DIY Audio Electronics from Zynsonix.com

With the resurgence of vinyl over the last decade manufacturers have taken notice and there are more offerings than ever for new vinylphiles. Not only do we have a great selection of turntables from VPI, Clearaudio, Music Hall, Marantz, Pro-Ject, etc. but there are lots of great new accessories as well to enhance your vinyl listening experience.

As we all know, listening to records can be a little inconvenient compared to firing up a Spotify playlist, however there are a few new items to the market that can help you out. If you're like me and can't always immediately get up at the end of a record side, you can now get a device that lifts your tonearm so your stylus isn't sitting there grinding on the end loop for several minutes. If you are using a $25 cartridges, this might not be a big deal, but there are some people out there using fancy pants carts that would be very interested in these.

There are a couple solutions I'm aware of: The Pahmer Enterprizes Q Up, which appears to be a great choice for value oriented listeners, and the Integrity HiFi Tru-Lift, which, in my opinion, seems a little more elegant and "at home" on a nicer turntable. The job of these devices is relatively simple, as the tonearm reaches the end of the record, it presses against a lever or switch and the tonearm is lifted to prevent the stylus from remaining on the record.

This post is going to be a brief review of the Tru-Lift. I say brief as it does exactly what its supposed to do without any notable flaw. Below is the no-frills packaging, which I actually appreciate. It drives me nuts when I purchase something I already knew I wanted and it seems like the manufacturer spent more on the package than the product itself... but I digress.

The Tru Lift is available in Brass and Stainless Steel, both relatively heavy metals. For the science savvy, the density of brass is between 8440-8730 kg/m³ and the density of stainless steel is between 7480-8000 kg/m³, so the brass units of the same size will weigh slightly more.

I like the look of the brass (and the added weight) but the stainless matches my setup better. I purchased the Deluxe package that included four different heights, should I ever change my turntable down the line. The units can be purchased individually for $199 (as of this writing) and are available/adjustable from 1 1/4" to 2 3/4", and the Deluxe package is available for $259.

The Deluxe set comes with 4 different sized bases

The units have a nice heft to them, which is good as you don't want them to fall over. Unscrewing the unit gives easy access to the internal mechanism.

The height is easily adjustable via set screw.

Setup took me a couple of tries, but once it's in the right spot you're good to go. I had to adjust a bit after these photos were taken, the little lever needs to be facing toward you to work as intended. There's a video that explains the setup. Once the lever is slowly pushed into by the tone-arm, the spring loaded piece slowly and carefully lifts up the tonearm. The unit remained stationary when the mechanism was struck, which is great as you don't have to move it back into place. To reset the mechanism, you simply push the spring loaded piece back down and you're good to go.

Overall I'm fond of the Tru-lift. It's a simple, elegant solution that does exactly what it is supposed to do and is easy to use. Pricing seems on par with other audio accessories, but may be a little high for those with modest systems. I'm actually surprised there are not more products like the Tru-Lift available, but it definitely satisfies a need for avid vinyl listeners. Highly recommended.

The Fine Print: Zynsonix Audio LLC and DIYAudioBlog have no affiliation with Integrity HiFi and/or the Tru Lift product. The author of this review was offered dealer pricing for the Tru Lift system as consideration upon request, however was not a factor in the evaluation of the product.

Dave over at Planet 10 HiFi has been instrumental in pushing the envelope for single driver speaker designs, including the much lauded Fonken and MiniOnken designs and the amazing Frugal horn which can be built with Mark Audio or Fostex drivers.

He also developed and patented the EnABL process which dampens and improves drivers (an interesting read if you have time). He's also developed many speaker cabinet designs, hosted a number of group buys, and has been a cornerstone of the DIY community.

Dave currently needs our help. Last year Dave's wife, Ruth, found him laying on the bathroom floor, ghostly pale and staring wide-eyed. Ruth immediately called an ambulance and Dave was taken to Vic General where an emergency CT Scan and speedy blood work prompted another ambulance to rush him to Royal Jubilee for emergency surgery less than an hour after leaving their home. It turned out that an abdominal aortic aneurysm had burst (one of multiple previously undetected aneurysms), his chest was full of blood and infection was raging through his upper body. Two gifted surgeons spent over 10 hours working valiantly to save his life. Dave survived the surgery to replace his entire aorta, top to bottom, and was kept in an induced-coma for almost a week to allow the body to begin to heal. The surgeon said Dave had incredible tenacity to make it through the surgery.

Fortunately, Dave just got back at home last month and has been slowly recovering, but as you can imagine there are many expenses associated with medical difficulties of this magnitude and being out of work for so long.

I encourage you to join in the GoFundMe to help out Dave and Ruth as they traverse this challenging time in their lives, especially if you value the great things Dave has done for the DIY community. You can also see the latest updates at DIYAudio.

In Mid-March, the prolific DIYer Pete Millett introduced a new hybrid headphone amp called the NuHybrid using the Korg Nutube 6P1. The design is similar to the original Millett Hybrid, which spawned both the exceedingly popular Millett MAX and stripped-down Starving Student builds. The Starving Student was super-popular as it could be built for as little as $35, which is unheard of for an amp with two tubes.

To shake things up (Millett designs are rarely status quo), the old car radio tubes were eschewed for the new Korg Nutube. The Nutube is a low-power, directly-heated dual triode tube built using a process originally used for Vacuum Fluorescent Displays (VFDs) and emits a bluish-white glow when the tube is powered up. The Nutube has been popular with DIYers in Japan since it was released at the tail-end of 2016, but hasn't really caught on with DIYers elsewhere, at least yet. The cost of a Nutube is around $50, which may seem a little steep, but two noval signal tubes will set you back at least $30-35 these days, along with another $5 for sockets and the potential to have to replace them in a few years, which makes $50 not seem all that bad.

The Korg NuTube

One of the nice things about the design is you don't have to feed it plenty of amps. The whole thing runs off of a 24V power supply, so it is much safer than a typical tube-based build. A pair of OPA551 op-amps to drive the headphones, but others can be rolled in for a different sound signature. Pete has made the design so it can be built cheaply (~$120) and placed in a Serpac plastic case. Much like Pete I don't like status quo, so I'll be building a case from scratch for my NuHybrid amp. I wanted to make the amp look like an old tabletop radio, so a wood frame would be needed.

A quick trip to Home Depot yielded a 6ft long by 3.5" wide piece of maple.

A little bit of routing and a few 45 degree cuts on a miter saw and we have a frame. Note the inside of the frame is rabbeted so the front and rear plate can sit flush. The 5/8" pieces in the middle are for screws to hold the plates in place. This is a photo after an initial coat of Minwax Pecan colored stain and seal combo. Yes I know it's sacrilege for anyone who works with wood regularly, but it's quite and easy.

Frame to hold PCB inside

The board is quick and easy to populate and should take even the most OCD solder slinger less than 3 hours. Below is an image of the PCB. The checkered areas indicate where double-sided tape is applied to the board to hold the NuTube in place.

NuHybrid unpopulated PCB

Below you'll see my PCB about 90% populated. I changed a couple of the parts in the BOM. The BOM calls for Wima polyester, but you can switch them out with Polypropylene for about $2.50 more and they fit without issue. I also went with Elna Silmics in the power supply. The Silmics sport a 7.5mm lead spacing versus 5 on the Nichicons, so they have to be pressed into place otherwise they'd stand crooked. They also encroach a bit on other areas of the PCB, so the Wimas needed to be mounted on the bottom. I also went with Takman carbon film resistors in most areas. The 1/4 watt variety are only 36 or so cents a pop at Sonic Craft, so it won't break the bank to use them.

Note the large-and-in-charge Silmics in the power supply section

I picked up two aluminum plates 1/8" thick for the front and back. I usually get them pre-cut from eBay but will also use a miter saw with a metal blade if the size I need isn't available. The back of the unit needs holes for four RCAs and 24v DC. Although I doubt the unit gets very hot due to the low power requirements, I drilled a hole pattern at the top for heat to escape, as with wood it will trap it in otherwise. The aluminum is spritzed with Hammertone paint in a copper finish.

1/8" thick aluminum plate with holes for RCA, DC

More to come...

Please remember that building/modifying circuits can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard.

This guest post is brought to you by my friends at Headphone Ninja. Anyone following the blog knows I love headphones, and Jo-Ann and company have culminated four tried-and true classics to discuss.

Studio headphones fill the market today. However, many of them are either far too expensive or far too inaccurate when it comes to meeting the referencing demands of producers and audio engineers. While everyone would love to own a pair of the sleek Sennheiser HD800s or the beautiful Japanese cherry birch wood Fostex TH 900s, we don’t all have a Hans Zimmer’s budget.

In this post we explore four of the more preferred headphones available in 2017 that are well suited to the modern day studio.

Closed-back headphones

Audio-Technica ATH-M50X

Comfort is key when it comes to long studio sessions. The generously padded earcups and adjustable headband of the ATH-MX50 provides comfort, and while the headphones do clamp down reasonably hard, they do not physically strangle the life out of your temples. They are slightly heavy at 10-ounces, but this should not be a deciding factor for those looking to use these in a studio environment.

The ATH-M50X is fitted with large 45mm proprietary drivers that deliver exceptional clarity. Some individuals who have used these thought that the bass is slightly high, but the mid frequencies are fairly well represented. The higher frequencies also appear to be slightly bright, but not to the point of fatiguing the ear. The 90-degree swivelling earcup is great for single ear monitoring and the frequency response ranges from 15 - 20,000Hz.

Sony MDR7506

Introduced back in 1991, the Sony MD7506 has remained a firm favorite amongst many looking for high quality and reliable headphones. Their durability is as decent as a pair of plastic headphones can get, with the only real issue of deterioration being the earpads on the cups, but these are replaceable. At around 8-ounces, they are light enough to not burden the wearer much.

The MDR7506’s frequency response ranges from 10 - 20,000Hz. It has revealed a solid bass response in tests, albeit slightly bumped up in the 60 -100Hz range. Mids remain fairly flat while the low treble to the high treble frequencies are quite inconsistent; the sibilance range is slightly boosted and can be slightly piercing to the more sensitive ears. The soundstage is decent for a closed-back pair of cans. They have an 63-ohm rated impedance and their low leakage is also suitable for recording purposes.

The coiled 9.8-inch cord is more than enough for studio environments and it does come with a ¼ inch adaptor. The Sony MDR7506 gives many mid-range referencing cans a run for their money.

Open-back headphones

Sennheiser HD 650

The Sennheiser HD 650 are slightly pricier, but it seems important to add these cans for those who enjoy the spacier sounds that open-back circumaural headphones offer. The suede-like fabric is a nice touch on the large, encompassing cups that house the efficient neodymium magnets.

The slightly under-emphasized low bass frequencies with the minor boost on the high bass gives the headphones a more natural sounding low end. The mid range responses are pretty much flat throughout and the treble frequencies are consistent. Their impressive frequency response coupled with the spacious sound created by the deep drivers and open-back design makes these excellent for critical listening.

Needless to say, their isolation is pretty much non-existent, making these more suited to quieter environments. They are also less suitable for recording purposes, because they do leak quite a bit of additional noise, which in turn will bleed into your microphone.

The Sennheiser HD 650 is an excellent referencing headphone and offer an awesome frequency response, though they are less suitable for recording purposes however.

Editors Note: The 650s can sound a little dull in the treble with the stock cable in some setups. A replacement featuring silver-clad copper can bring out the highs. Check with Zynsonix for additional details.

AKG K712 PRO

The AKG K712 PRO are another great choice for mixing and mastering purposes. The design is slightly bulky, but they are purposefully built for studios, so that is completely understandable. The memory foam earcups captures the shape of your head, but they are rather large. Sound wise, they deliver a spacious and accurate audio reproduction, but the sound is a bit warmer in the upper bass. Still, it is well controlled overall. The mids are represented accurately.

Sensitive ears may find the slightly boosted (and somewhat inconsistent) higher frequencies a tad overwhelming, as they can sound harsh. The frequency response ranges from 10 - 39,800Hz in its entirety and it has a low harmonic distortion.

As a whole, the AKG K712 PRO have a natural sound and are well suited to intensive referencing sessions. The open-back design means they are more suited for mixing and mastering in studios.

Wrap up

This is by no means a comprehensive guide to selecting studio headphones, but a look at some of the more popular headphones around at the moment for any type of studio. While they may mostly be mid-range headphones, they perform well within their specific categories and are well suited for studio use.

Op-amps, or operational amplifiers, are ubiquitous in solid state amplifiers. These little integrated chips are simple little building blocks designed to work in a wide range of electronics such as PCs and other devices. For those of you not familiar, op-amps are like vacuum tubes for the solid state world. Most manufacturers use sockets so the op-amps can be swapped, and each have a difference sound signature (e.g. warm, revealing, etc.). Some have voltage requirements that make them only compatible in certain designs, etc. Some are affordable (the LM4562 which runs less than $1), and some are expensive like the popular $25 Burr Brown OPA627.

Burson Audio is a company on a very short list of providers of discrete op-amps. Rather than having a bunch of teeny tiny components shoe-horned in a chip the size of a fingernail, Burson creates devices that plug into op-amp sockets that use a fully discrete set of diodes, resistors, etc. I remember my first purchase of several of their discrete op-amps roughly six years ago, trying to breath some additional life into a Music Hall DAC. While their first iterations weren't super easy to install, they made a world of difference in the sound department. Everything was much more natural and effortless sounding than the stock op-amps which I believe were mid-grade models from Texas Instruments.

Fast forward to today and we have the Supreme Sound V5 and V5i Opamps. The V5 features fully discrete components including 0.5% tolerance metal film TKD resistors, hand-matched FET transistors, and a sleek looking red cover.

The Burson V5 (left) and V5i (right) in their packaging

Note the size difference between the two units

A fixed 8 pin DIP socket makes installation much easier

It's also a smaller form factor than the originals, which is crucial for installing in tight circuits / spaces. The V5i is a hybrid of sorts which includes both IC and discrete components, but is much smaller and should fit in virtually any build. Do note that these units can only replace op-amps as noted on the Burson site:

Dual Op-amps:
AD823, AD823AN, AD8066, AD8620, AD712, AD827, C4570, JRC4556AD, JRC4580, JRC5532, JRC5532D, JRC5534, LF353, LM4562, LME49860, LM833N, MUSES8920, NE5532, NEC4520, NEC4570, NJM2068D, NJM2114, NJM2214D, NJM4558, NJM4558D, NJM4560, NJM5532, NJM4558P, OP275, OPA1612, OPA2277PA, OPA2132, OPA2134, OPA2604, JRC4558, RC4558D, RC4558P, TL052, TL072, MUSES01, MUSES02, MUSES8820, MUSES8920, MUSES8832, BA15532

Single Op-amps:
NE5534, LT1122, TL071, OPA134, OPA627, AD811,AD829, AD844, OPA604, AD8610, AD711, AD797, LME49990, LME49710

Installing them in a unit that is not compatible could cause undue stress on the components / oscillation, etc.

More to come...

I've heard many positive impressions from fellow audio enthusiasts regarding LessLoss power conditioning products and have always been curious about how they stack up. The unique construction of the previous Firewall using exotic materials like Panzerholz, a plywood-like bulletproof material with high damping properties, and carbon fiber, had left me very curious. The new Firewall is a much more affordable endeavor, starting as low as $198 for the DIY version, $385 for the USB version and $410 for the power outlet version.

As nearly all of my gear is completely DIY, I took a special interest in the DIY version of the Firewall. I've come accustomed to the typical simple resistor/capacitor/inductor networks in discrete filtering circuits (those you commonly find in an audio power conditioner, the filtering IECs that are sometimes installed in DIY tube amps, and other DIY implementations), but have never seen an alternative to these.

The Firewall DIY module is relatively small, roughly 2" by 4" and has and input and output for L (line/hot) and an input and output for N (neutral). There are unique ripples/patterns in the surface of the solder mask which cover the copper underneath.

Click to enlarge the photo to see the solder mask

Five Firewall units lined up

Per the instructions, The Firewall units can handle up to 1000VDC and can be stacked and/or run in series to increase the level of the filtering. Kapton tape or discs is recommended to prevent the inputs and outputs from shorting.

Four LessLoss Firewall Modules stacked in series

There have been tests of up to four parallel stacks of eleven boards if you want to go super crazy ;) Do note that "LessLoss will not be held responsible for the fate of your equipment or health or other personal property should you choose to use our product in your own designs", so stick with the off-the-shelf units unless you know what you're doing.

More to come...

MHDT has a cult following in the DAC world, and for good reason. They may not be featuring all the latest chip designs and 24bit oversampling converters, but new technology doesn't have a direct correlation with better sound. The equipment designed in the 1960s from H.H. Scott, Dynaco, Harmon Kardon, Marantz and McIntosh is still well sought after today for it's excellent sound qualities. Granted if you are a purist and want a straight line response curve, these won't scratch that itch, but if you want to enjoy the music they'll fit the bill perfectly well.

The MHDT Havana comes after the venerable Paradisea 3, which is an excellent sounding example of a NOS (non over-sampling) DAC with a tube buffer. Both the Paradisea and the previous Constantine make use of a Philips TDA 1545A DAC chip and come in a handsome translucent dark acrylic. (See the posts covering the modification of the Constantine and the Paradisea.) Unlike the previous two, the Havana uses no op-amp for I/V conversion. Opamps are often looked down upon as the tasks performed can generally be done better with discrete components. The Havana features a 16 bit R-2R Burr Brown PCM56P DAC, and uses a tube-buffered output stage (GE5670).

A stock MHDT Havana DAC

It's interesting to see the progression of MHDT DACs over the years. Not only are the op-amps going away, there's more aluminum panels and less acrylic body panels, as well as the utilization of more surface mount components on the PCB. The circuit boards have also become more robust, which is nice when exchanging components. Other components generally stay about the same, from Nichicon Fine Gold electrolytic caps in the power supply, Nichicon Muse caps and Sanyo/Panasonic OS-CON caps elsewhere, as well as MHDT brand film caps which I imagine are sourced in Taiwan.

The stock PCB removed from the chassis

I generally like to replace the Muse caps with Elna Silmic II for a little more warmth, as well as Soniccraft 600v 0.1uf and 0.22uf Sonicaps for the smaller film caps, as Sonicaps are a great value and are small in form factor compared to most other audio capacitors. For the output caps, replacing with the best quality that fits that you can afford is generally the best strategy, as they are directly in the signal path.

Below is a partially modified unit. Note the Nichicon FG power supply smoothing caps have been bumped up to 3,300uF (there's plenty of room), most film caps have been replaced, and I had just started installing the Elma Silmic II caps.

Partially modified PCB, note larger Nichicon FG filter caps, Sonicap film caps

The RCAs on the unit are perfectly fine, but I was able to source some nice ones with teflon insulation, so I installed those. The unit on the left is the teflon insulated one, it looks a little bit different but fits perfectly.

Teflon RCA left, stock RCA right

The RCA for the digital coax was replaced with a Vampire BNC (about $13-14). I chose Jupiter HT paper in wax caps for the output. They've served me well in other applications and have a nice natural presentation. I happened to have several Kiwame resistors that I installed in the tube buffer.

The completed mod

The Jupiter 2.2uF 600V caps just narrowly fit in the Havana chassis. I tombstoned one of the Sonicaps to ensure there was enough clearance. One thing I found odd was MHDT never grounds their DACs. I understood there wasn't much of a point with an acrylic chassis, but now that they're brushed aluminum, might as well use it as a shield. The electroplating is very thick on the chassis and needs to be sanded away to make contact. I used a Dremel on the metal under each screw and put everything back together, checking for continuity with a multimeter. I had to re-hit a few of the holes but eventually got there. I ran a wire from the ground on the IEC to circuit ground and connected to chassis ground, so now we have a safe and shielded DAC.

Boxed back up

Everything is sounding very nice so far. The op-amp-less design is a little more forward than the Paradisea (which is very warm and syrupy), but still very natural sounding and makes for an enjoyable listen. When I say forward, I simply mean related to other MHDT DACs. It's still warm compared to 95% of DACs on the market. I still have to let the Jupiters burn-in, which in my experience just takes a couple of nights of audio running through them, but everything will open up once they do.

The Fine Print:

Please remember that modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a posted modification and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard.

I was browsing around the net looking for a quick and fun little project when I discovered Fred's Amplifiers. Fred has a small site with a number of PCBs and kits, most of which are portable headphone amplifiers, along with a portable guitar amp kit and a couple of crossfeed units.

I decided to order the 12AU7 Valve headphone amp PCB. It's a single sided PCB and was only $10, with the BoM (bill of materials) posted on the site. I went with the PCB versus the kit as I have tons of parts lying about, but the kit is only $45 if you want to go that route, just note you need to buy the chassis (Hammond 1593) and A/C adapter (12v 1A Regulated DC supply, center pin positive) on your own. The unit only requires around 25 parts to complete, so you'll be done in no time. The Op-amp in the kit is the venerable JRC 4556 used in most CMOYs / RA1 clones and similar portable low-power headphone amps.

I went with the translucent blue version of the Hammond case (1593KTBU). Trimming into the plastic Hammond case requires you to go slowly on the drill press or the plastic will crack. You may want to buy two cases (they're $4 each) just in case your holes don't line up perfectly.

My unit features Takman carbon film resistors, a diffused 5mm amber LED, a milled aluminum knob from Kilo, and 470uf 16v Elna Silmic II capacitors. Elna Silmic II are widely accepted as the best electrolytic available for the signal path. They are a tough fit, and will require you melt down the PCB standoffs on the bottom of the Hammond case to get everything to fit nicely. You could also drill holes at the top of the chassis for clearance, but that reduces the portability in my opinion. The AC adapter I went with was a $10 Meanwell unit - SGA12U12-P1J. I'm sure there are cheaper, I just plugged the specs into Mouser and bought the first one on the list.

Here are a few more photos of the amp:

There's nothing challenging or unusual about this build, so if you'd like a fun and affordable little portable tube headphone amp, put this one on your short list.

MHDT has a cult following in the DAC world, and for good reason. They may not all be featuring the latest chip designs and 768kHz inputs, but new technology doesn't always have a direct correlation with better sound. Case-in-point, the prices of 1960s equipment made by H.H. Scott, Harmon Kardon, Marantz and McIntosh all continue to increase from more and more audio enthusiasts desiring the musical qualities inherent from the Golden-era of audio. Granted if you are a purist and want a straight line response curve, these won't scratch that itch, but if you crave a warm musicality MHDT has few peers that can rival.

The Atlantis is one of the latest offerings from MHDT, and much like last generation's Havana, along with the current generation's Stockholm, features a R/2R Multibit DAC. The Stockholm, Atlantis and Pagoda are unique as they have discrete transistors in the I/V stage, no opamps at all. Opamps are often looked down upon as they can be a "one-size-fits-all" type of solution, and the tasks they perform can generally be done better with discrete components. The Atlantis features a AD1862-J DAC chip, and uses a tube-buffered output stage (GE5670).

MHDT Atlantis with stock internals

Luckbad, a member at headphone enthusiast forum HeadFi, created an AWESOME table that compares the more recent MHDT DACs:

Mhdt Labs DAC Families
Models	Havana	Havana 2	Stockholm 2	Atlantis	Pagoda	Steeplechase
Spec	Havana	Havana 2	Stockholm 2	Atlantis	Pagoda	Steeplechase
Input Capacity USB (Max)	16bits/48kHz	24bits/192kHz	24bits/192kHz	24bits/192kHz	24bits/192kHz	24bits/192kHz
Input Capacity SPDIF (Max)	24bits/96kHz	24bits/192kHz	24bits/192kHz	24bits/192kHz	24bits/192kHz	24bits/192kHz
Output Format	16bits	16bits	16bits	20bits	24bits	24bits
Digital Receiver Chip	CS8414	CS8416	CS8416	CS8416	CS8416	CS8416
USB Chip	CM102AS+	CM6631A	CM6631A	CM6631A	CM6631A	CM6631A
DAC Chip	PCM56P-J	PCM56P-J	PCM56P-J	AD1862-J	PCM1704	AK4396
DAC Chip Construction	R/2R Multi Bits	R/2R Multi Bits	R/2R Multi Bits	R/2R Multi Bits	R/2R Multi Bits	Delta-Sigma 1 Bit
I/V Stage	Voltage out DAC's Internal OPAMP		Current Out Discrete Transistors I/V, No OPAMP, No feedback			Current Out AD847AQ as I/V
Tube Buffer	Tube Buffer with 5670/2C51
Output level	2.6V	2.6V	3.0V	3.0V	3.0V	2.8V
Output impedance	32 ohms	32 ohms	32 ohms	32 ohms	32 ohms	32 ohms
Inputs Available	3 Inputs -- USB/ RCA/Optic		4 Inputs -- USB/RCA/BNC/Optic
USB Input Topology	USB1.0	USB2.0
USB Driver for Win XP/W7/W8	No Needed	Yes, Needed
USB Driver for Linux/Mac	No Needed
Dimensions clear (WxDXH)	260X150X60		276 x 150 x 60 mm
Dimensions w/ socket	280X170X60		295 x 170 x 60 mm
Weight	1.8Kg		2Kg
Box Color Avialable	Black Only		Black/Silver Selectable			Silver Only

It's been fun to see the progression of MHDT DACs over the years. The chassis used to be made completely out of acrylic. Now only the front cover is acrylic (a nice thick acrylic) and the rest of the body is make of aluminum panels that screw together. In addition, the op-amps are going away and there is more utilization of surface mount components on the PCB. The circuit boards have also become more robust, which is nice when exchanging components. Other components generally stay about the same, from Nichicon Fine Gold electrolytic caps in the power supply, Nichicon Muse caps and Sanyo/Panasonic OS-CON caps elsewhere, as well as MHDT brand film caps which I imagine are sourced in Taiwan.

I generally like to replace the Muse caps with Elna Silmic II for a little more warmth, as well as Soniccraft 600v 0.1uf and 0.22uf Sonicaps for the smaller film caps, as Sonicaps are a great value and are small in form factor compared to most other audio capacitors. For the output caps, replacing with the best quality that fits that you can afford is generally the best strategy, as they are directly in the signal path.

MHDT includes a larger toroid in the Stockholm, so I wanted to upgrade the power supply in the Atlantis. I checked Mouser and Digikey for a larger toroid and no one seems to make a unit with the two secondaries needed, so you'd either have to have two toroids (which wouldn't fit in the case) or snag one from MHDT directly. The larger unit from the Stockholm fits perfectly well in the Atlantis, you don't even have to drill a new hole to mount it. While they look similar in size, the larger one is twice the volt-ampere rating.

Comparing the larger toroid from the Stockholm (black) to the stock Atlantis unit (white)

Teflon RCA left, stock RCA right

The Jupiter 2.2uF 600V caps had to be shoehorned to fit. While they fit fine in the Havana (albeit tightly), the Atlantis opening was a little narrower despite the slightly larger chassis footprint. Reviewing my options, I decided to stand the caps off the board slightly to clear the small Oscons and sand down the heatsink to allow the capacitor to wedge up next to it. It doesn't get terribly hot, so we'll see how that goes.

While I don't go out of my way to get audio fuses (I'd be pretty grumpy if a $70 fuse broke, and I'm a little skeptical as the resistance in a fuse is minimal), PCX had a few on sale for $12 from HiFiTuning so I figured I'd give it a shot. $12 is a drop in the bucket for audio gear as you know. Swapping the 400ma stock fuse with the gold fuse seemed to increase the higher frequencies (by a small degree), so it may be counteractive when you're after a warm-sounding DAC. I'll be testing more, but that's my initial finding. I may try in some other equipment to see if that's consistent if they're still cheap for my next order ;).

Click to zoom in

The DAC sounds excellent. More resolving and clear than my Paradisea and less forward than my Havana. It's my favorite sounding MHDT so far and very easy to listen to. I hear the Stockholm is even better (based on forum banter around the web), but this is a DAC for a few bucks less.

UPDATE: I found some 30mm aluminum feet with a damping ring on Aliexpress that are a nice step up from the stock plastic feet. They're quick and easy replacement and are less than $10 for a set of 4.

The Fine Print:

Version 2 of AMB's σ11 (Sigma 11) regulated power supply has been out since June of 2015, but I'm finally getting around to building my own. AMB (Ti Kan) is mostly known for his headphone amp and DAC designs, but his site offers several power supply options as well.

The σ11 is a top notch DIY single-rail linear regulated power supply known for low-noise, high-current, excellent line/load regulation, wide-bandwidth, and stability. The circuit features all discrete components and high-current MOSFETs for the output. Per AMB, the σ11 is a great choice for DIY headphone amplifiers, pre-amps, DACs, network media players, and other devices needing a single-rail regulated power supply.

AMB o11 Power Supply PCB

This power supply is a pretty quick build with ~40-50 total parts. A typical builder can populate the PCB in an hour or two. AMB offers the PCBs for sale on his site, along with some of the necessary parts. The rest you'll need to get from Mouser / Digikey or your favorite parts supplier. I went with all stock parts aside from an Antek 50VA toroid instead of the Amveco TE62062 25VA as it was much more reasonably priced, albeit a little larger. Because of this, the Hammond 1455N2201 was the best chassis size for the job.

Antek 50VA toroid

Rather than leave the Hammond case plain, I wanted to give it a little more character. I sourced a piece of wood online which didn't have a species listed, it simply was called Asian burlwood. I cut a front plate with about a 1/2" overhang in each dimension and drilled holes for the screws to line up with the existing screw holes in the Hammond case. Two coats of satin lacquer gave it a nice sheen.

Asian burlwood front cover

Two holes were cut into the top of the Hammond case and it was sanded down with 180 grit sandpaper to reveal a grain-like anodization pattern. Powercoated aluminum grating was secured with adhesive underneath the holes... then a permanent furniture market was used to give the bare aluminum a bronze-like color.

In the rear, I've installed a pair of outputs. The board offers up to four outputs if desired, but an appropriately sized toroid should also be used. If you're not sure about the rating needed, the forum on the AMB website can be very helpful as other people have likely already asked the questions you are wondering.

AMB σ11 Sigma power supply rear

A Fender-style pilot light was installed up front with an Amber jewel and LED.

AMB σ11 Sigma power supply front with pilot light

All done! Now I have a nice regulated 24v power supply now with a pair of outputs.

Anyone who does DIY knows it can be expensive at times. As the dollar weakens and metal commodity prices rise, so do capacitors, resistors, transformers... you name it. There is a great way to get around that though, with surplus and buyout parts. There are many companies out there that procure these parts from discontinued products, company closures, old military stock and other sources and flip them at a discount. While you may need to modify your specs to accommodate some of these parts, they generally work perfectly well. Apex Jr. is one I frequent, and Partsexpress is also a great source for some unusual finds.

Partsexpress recently procured a buyout of Footnote electric guitar 5 watt amp assemblies and are passing them along for $15 a pop, a great deal given the complexity and quality of the unit. For $50-100, you can put together your own miniature guitar amp for practicing or small gigs. I decided to put one together as a gift for someone I knew would appreciate it, so I ordered the unit along with an A/C adapter, full range driver, grill and a few other items. Below is a list of parts with some embellishments that can be included as desired.

Inventory List

Footnote 5 watt amp assembly	$15 from PartsExpress
9V 1000mA A/C Adapter (center pin negative)	$5 from PartsExpress
GRS 3FR-4 3" full range driver	$5 from PartsExpress
4" wire mesh grill with gold accent	$1.50 from PartsExpress
Speaker Caulk	$1-2 from PartsExpress
Leather look strap handle	$5 from PartsExpress
Weather stripping	$4-6 at your local hardware store
Metal corner accents	$3-5 shipped on eBay
LED accent bulb	$2-3
Automotive damping sheets	$10 on eBay
Wine box	$17 on Amazon
9V Battery clip	$4 on PartsExpress
Equipment feet	$2-3 on PartsExpress

As you can see, nearly everything can be sourced from PartsExpress. Some other things that I had on hand that were needed were some 24 gauge wire, screws, solder, wood stain and seal, 2.5" hole saw, drill, etc.

The only modifications needed for the wine box were drilling the hole for the speaker, cutting the hole for the amp unit, and removing the little wood piece that would separate the two bottles of wine. I had a spare piece of mahogany that I used to reinforce the baffle area for the speaker. Drilling the parts in place like the handle and feet only takes a few minutes. There is a small amount of speaker caulk to seal the driver and amp within the box, the interior is covered with the automotive damping sheets, and the weather stripping helps seal the box around the perimeter.

The wiring to the driver connects directly to board via an adapter, but to add the LED pilot light I needed to solder some leads to the on/off switch so it would only turn on when the amp is on. The unit can also run on battery power, so I soldered another couple of leads to the board and ran them down to a 9V battery clip. As the amp creates a modest 5 watts, the battery should last a while. There was room in the box for the A/C adapter, but care was taken to ensure it would not short out or damage the board. After the photo below I added some additional wood to secure it in place.

The SKB Footnote unit was actually made as a practice unit for guitarists that wanted to plug in a bunch of effects pedals, as it offers 8 separate power outputs for them. Per my research, the unit came with a 6" Eminence speaker, real-estate for all the pedals and cost around $300, so $15 is a bargain for the amp unit.

The original SKB FootNote unit - neat idea

The FootNote Amp module installed

Even if you're just using the Footnote as a power supply it's worth the price of admission. The only trick is you'd have to build power cables to work with it as the kind it uses are hard to come by (9v center negative on both sides). PartsExpress does show you how to make one though.

Here's the unit in its finished glory. I used a woodburning pen to decorate the surface of the unit and personalize it. I applied the stain selectively to allow some of the objects to stand out a little bit. Should make a great gift!

If you are looking for a simple guitar amp circuit with great tone and you don't need a lot of power, the Champ 5F1 is a great choice. The Champ 5F1 was introduced by Fender in 1958 and were produced in tweed covered cabinets until 1964 when the "Blackface" circuit and cabinets were introduced. The 5F1 features 6 capacitors (+1 additional bypass if desired), 12 resistors, 3 tubes, and one potentiometer. Not only is a simple circuit harder to screw up, it's easy on the wallet too! The output is a modest 5 watts, which is great for practice and studio work. There are some chunkier transformers that let you bump up to 15 watts with a tube and resistor swap if desired.

The Champ 5F1 starts its life as a turret board. If you're not familiar, these were very common in the 50s and 60s, where axial capacitors and resistors were lined up on the board. Why I wasn't alive back then, I assume this made electronics easier to fix for the visiting repairman, who could simply look at the board and see where the problem component is and replace it easily. The use of these faded as electronics were more commonly replaced rather than fixed. You can easily find one pre-made for the 5F1 on Ebay, Watts Tube Audio or buy a black FR4 board, drill the holes and affix the turrets yourself (It's fun!). You can get the tools to do that at Watts Tube Audio as well... I encourage you to support them, they are a great small business and a source for myriad board designs.

A classic turret board

Adding the caps and resistors is easy, just ensure the leads are long enough. Some carbon comp resistors from Mouser were too short I found. The parts used here are Illinois Capacitor electrolytics and Koa Speers / Kiwame resistors. Some people prefer Sprague for the axial caps, however I've heard from a trusted source that he's experienced failures first-hand with them, so I steer clear. F&T is the only other high voltage axial capacitor maker that I am aware of. It's a niche market, so we're lucky we have three options.

Next, you'll need a chassis. While I often drill my own, sometimes it's nice to take a little break and get a pre-fab one. This one is from Tube Audio Supply and is very high quality. They supply a number of colors in addition to the typical polished/chrome, great for a personalized look.

Tube Audio Supply 5F1 chassis in Oxblood Red

After much reading regarding transformers, ClassicTone by Magnetic Components seemed to be the best bang for the buck. I chose the 10-18019 model, 5/15 watt version for power. As you can see below they aren't too easy on the eyes, there's quite a bit of errant varnish.

ClassicTone 10-18019

It also may have been the end of the day on Friday when they put this one together. The nylon washer broke off inside so the builder put a few lock washers there instead.

A little bit of elbow grease, paint and new screws/nylon washers go a long way.

Before

After

...too bad, as I liked their logo on the bell. Aside from the visual issues, the transformers seem very solid.

Below is the unit with the mostly-populated turret board in place. The light is the typical Fender jewel style that I like to use on pretty much everything. 1/4" jacks are Switchcraft, and tube sockets are Belton. The pot is a high quality PEC unit from Canada, which I feel is worth the extra scratch over CTS / Alpha.

Getting all the wiring correct is important, and a little tricky as there isn't a ton of room once everything is in place. I highly encourage you to visit Rob Robinette's fantastic page on the Champ 5F1. It lays out all the parts and their purpose, as well as optional parts. Rob is an awesome guy. I once messaged him to donate some funds for site maintenance as I was building one of his designs and he told me "just buy yourself a few beers, I do this because I love it". Also on the page are various guitar mods, headphone circuits, car tweaks, you name it.

Next we need a cabinet to drop this puppy in. I had one custom made for me by a Jim, who goes by tubeampcabinets on Ebay. The work is phenomenal, with Spalted Maple and Purple Heart accents. I highly recommend you reach out to him via Ebay to get yourself a nice cab yourself.

Beautiful Cab from Jim, Ebay user TubeAmpCabinets

While it's not necessary, I had some spare damping material which I added to the box to prevent standing waves.

The driver I chose is an 8" 4 ohm ceramic from Jupiter Condenser. Anyone who's followed my blog knows I love Jupiter's capacitors, they have a warm, natural tone that does music right, so I HAD to try a Jupiter driver.

Jupiter Condenser 8" ceramic cone woofer

It's a beauty in what looks like a hammertone green powdercoat. For $50 it's a straight-up bargain, considering the caps can cost many times that. The AlNiCo versions are notably more expensive, but there isn't an 8 inch version of those yet. It will likely give me an excuse to build something a little bigger ;)

Below you'll see the unit with everything fitted, including the Red Astron Jupiter tone caps and a burgundy hospital grade power cord that I purchased from a surplus electronics store. As the PEC pot did not include a switch, I added one, a surplus Carling SPST, thus the 2 Amp fuse had to be mounted inside the chassis vs. a panel mount.

One of the greatest things about the Champ is that there are many NOS tubes out there for dirt cheap. I got a handful of 5Y3 rectifiers and 6V6 power tubes for a song online. You'll find plenty for around $10 each. The 12AX7 is going to be a little more pricey , but still much more reasonable than say a 6922. I had a spare Yugoslavian Ei from the 80s that I dropped in, nice and smooth sounding. If NOS is too expensive, there are many good new production 12AX7s out there. I personally like the long-plate Sovtek 12AX7-LPS, which are about $15 a pop.

Cool looking red power cord sourced from an electronics surplus shop

The knob I chose was one I had in-hand. It needed to be milled a bit to fit, but I liked it a little better than the red chicken head knob I had selected for the amp initially.

Milled aluminum knob for a custom look

What a beauty!

The result, beautiful tone from an amp that's very easy on the eyes.

I've seen a few designs out there that starve a tube filament to maintain a low voltage and still provide nice results. The Matsumin Valvecaster is one of them. For those afraid to work with tubes due to high voltage (cue Electric Six, "Danger! High Voltage!"), this keeps the power at safer levels. It also allows a 9v battery to be used (or 12V) but will consume them fairly quickly... so an AC adapter is recommended.

The design is nice and simple, and for beginning builders it's not too hard to follow the circuit visually. There are a couple of variations floating around, so if you're looking at multiple schematics or diagrams, be aware that they aren't all the same. Other builders have created their own unique pedals based on this design, but the values of the parts are different, so again, be aware ;)

Matsumin Valvecaster schematic from hgamps

My favorite diagram/illustration was from David Smith. The input and output jacks are included as well as the 3PDT switch to bypass the circuit. David's illustration is intended for a turret board, but if you prefer point to point it's still easy to follow. Be sure to note the orientation of the 3PDT switch, it won't work if it's oriented differently (i.e. twisted 90 degrees).

David Smith's diagram offers an easy-to-follow layout

Here's another diagram from Stompboxed, it's a little harder to follow but still helpful.

Another diagram for reference.

You'll probably want to use one of the larger Hammond 1590BB (or Hammond-style) chassis as I don't think trying to shoehorn this into a 1590B would be terribly easy. The 1590BB is available from the usual suspects, Mouser, Digikey, etc. in a variety of powdercoated colors. You can also go to Mammoth Electronics and get some much cooler paintjobs for a few more bucks, or go crazy with some waterslide decals... the sky is the limit. For this project I went with a purple Hammond 1590BB ... you can almost taste the grape looking at it.

These are cast aluminum, so you need to treat them a little more gently than something that's extruded (e.g. try to do more drilling on the drill press rather than punching holes). Punching out the holes with a tool can sometimes take away more metal than you anticipated.

I used larger Alpha pots in this build as I had them in the work-bin. CTS, Bourns and PEC also make good pots, and if you want to check out surplus, Clarostat and Allen Bradley are also great choices. The ceramic 9 pin tube socket is set against the chassis with a rubber "o" ring which can help quash microphonics. It's overkill for this build, but I had it in the bin. Beltons are cheaper and work great as well.

There is a corresponding PCB to be used with CNC tube socket as the solder tabs are quite small to solder accurately. These can be found on Ebay by searching for "9 pin PCB", and Partsconnexion also carries them.

The Russian PIO caps are a little on the large side and have metal shells, so they need to be carefully placed so they don't short any leads. They can also be covered with heatshrink. PTFE (teflon) tubing is placed on bare leads to ensure they don't short either. Also space needs to be given to the open-frame Switchcraft 11 1/4" jacks so they don't bump into any parts or wires when being inserted.

Using different colored wire during the wiring process can help you visually follow the circuit if it doesn't work upon plugging in for the first time. Having a rat's nest of the same colored wire makes things much more difficult.

Valvecaster wired up point to point

On top of the chassis a tube shield will be installed to protect the tube from an errant foot. You can find these in a number of anodized colors from Angela.com. I thought the gold looked nice contrasting against the purple.

Top of the Valvecaster with Tube Shield off...

...and tube shield on

Hope you enjoyed the build process of the Matsumin Valvecaster Effects Pedal. You can see it's pretty easy to build a great effects pedal without a PCB and just a few parts. Remember to use good quality parts like Switchcraft 1/4" jacks, Alpha or CTS potentiometers, etc. to ensure your new pedal lasts a good long while.

When I started doing research on which guitar pedals I wanted to build, the Electro Harmonix Big Muff may have the largest following of any pedal. Nearly every boutique pedal provider has a version of the Big Muff, and there are many forum posts arguing which Big Muff configuration is the best of the best.

After much digging, I found an extremely well documented PCB which can be configured to many different versions including the V1 Triangle, V2 Rams Head, V2 Ram's Head Violet Era, V3 Big Muff, Green Russian, or Civil War w/power booster... you can even tweak it to work similarly to the Black Arts Pharaoh... so lots of headroom to try different things. Best of all, the PCB is only $8, so you can experiment away on the cheap. Speaking of cheap, I highly recommend Tayda electronics, you can get most of what you need for a fraction of the price that Mouser or Digikey would charge. All the resistors, switches, op-amps, sockets, etc. I've purchased there work perfectly well. I do usually splurge on name-brand electrolytic caps from Mouser (e.g. Nichicon or Panasonic), but for everything else, Tayda has you covered.

Coda Effects Dolmen Fuzz on right

If you want to be cool, you'll get a nicely powdercoated enclosure for your Big Muff clone from Mammoth Electronics... or paint your own :) I chose a translucent blue powdercoat for this pedal. The documentation at Coda (PDF) has a printable template for your drill holes. Make sure to not resize the document when printing, otherwise you might have to order another chassis when your drill holes don't line up.

Using Coda's drill template makes things a snap

Adding the holes on the drill press

So purdy!

Now it's the fun part (at least for me), populating the PCB with parts. As you know, start with the small parts first (usually the resistors) and work your way up to the capacitors. I'm pretty OCD about this process. I measure the resistors to ensure they are the correct value, solder them on the bottom, trim the leads, then solder the top of the board. Most people just solder the bottom and trim the lead. No matter the method, it won't take you long to get everything in place.

Populated Coda Pi Fuzz board...sweet!

If you're wondering about the parts used, they are Wima film caps, Vishay Dale mil-spec metal film resistors, and a Panasonic electrolytic. They tend to be the preferred parts for audio people, but you'll likely do just as well with their cheaper counterparts. I followed the Ram's Head Violet Era bill of materials (BoM) for this particular build. I had a good listen to various YouTube videos before I settled on it as my favorite of the bunch. Many people like the Green Russian, so give that a good listen as well.

The cute little Alpha pots with non-conductive dust covers sit on the other side, no wiring to worry about. These are from Tayda Electronics if you are looking. "A" means audio log taper, and "B" means linear taper... so B25K means a 25K value pot with linear taper. Sorry, that will never show up on trivia night at your local bar.

Alpha pots all pointed at you like torpedos

Just a heads up, but shoehorning everything into a 1590B is a tight squeeze. I should have drilled the pedal switch a bit lower, but I still made out okay. The great thing is the pots hold the PCB in place, no need for standoffs.

So tight that I needed to mount the Panasonic capacitor sideways and give the transistors a bit of a gangsta lean.

The 1/4" plugs fit perfectly. As you can see nearly all the real-estate is filled.

And the final product, which sounds excellent. Lots of fuzz for your buck. The knobs are also from Tayda.

Hope you enjoyed the build process of the Coda Effects Dolmen Fuzz Pedal. If you'd like to get started with a versatile effect with exceptional documentation, this is a great choice. Remember to use good quality parts like Switchcraft 1/4" jacks to ensure your new pedal lasts a good long while. Until next time!

Wayne Colburn of PASS Labs was kind enough to release a new DIY headphone amp circuit into the wild, the WHAMMY, standing for Wayne' Headphone Amplifier Must Make Yourself. It's a nice simple build, no need to match parts or make adjustments, so it's perfect for the budding DIY builder. It's also inexpensive. The PCB, parts and chassis should be under $200 without much effort. Jim Tiemann aka 6L6 of DIYAudio has been kind enough to coordinate the project and has been instrumental in making it accessible. Having a headphone amp of this caliber available at this price is an incredible opportunity and I hope many can take advantage of it. If you're not familiar, Pass Labs is very

You can read more about the project here and boards can be purchased for a very reasonable price at DIYAudio. And you can learn more about the circuit design by watching this Youtube video:

Wayne Colburn of Pass Labs, the designer of the WHAMMY

I'll be briefly walking through my own build. I encourage you to also check out Jim Tiemann's build as it is more granular. My parts choices are also going to be outside of the standard BOM to some extent and will be more expensive, but DIY is fun because you have the freedom to make some unique choices without deviating from the original circuit.

As I knew I would have a little bit of extra headroom in the chassis I'd be using, so I added a piece of Dynamat between the board and the transformer just for a little bit of extra vibration damping. There's electrical tape over some of the larger contacts to prevent any shorting with the aluminum on top of the Dynamat.

Dynamat mounted on the PCB

After this, the power supply components were populated on the board. Normally, you would populate the small components all across the board such as the diodes, resistors, etc., however in this case populating the power components first allows you to test the power supply and ensure it is running properly and within tolerance before moving on. Review Jim's write-up for additional information on the measurements.

Please note the snubber capacitor (C20) should be an X-type, so you might see X1 or X2 in the model number. Before buying the capacitor, check the datasheet to ensure it is X1 or X2 rated. The lead spacing is 22.5mm. I personally used part 594-2222-336-10224 from Mouser. The PSU caps are Nichicon "For Audio"... for whatever that's good for ;)

Power supply populated and ready for testing

After the power supply is tested, fully disconnected, and the caps allowed to fully discharge, I moved along to populate the smallest parts first. If you've read my blog in the past, you'd know I really like Kiwame/Koa Speers resistors. These can be found at Mouser under SPR2 and are 40 to 50 cents each, rated at 2 watts which is far above what's actually needed. Not all values are there, so you can get the remainder at a boutique provider like PartsConnexion or just get some Vishay Dales at Mouser.

Adding the resistors

Then the rest of the parts are added. While Wayne mentioned that the Silmic IIs, which are now being produced in China, aren't as reliable as they used to be, I still like the sound of them so I went ahead and used them. They're over-rated too @ 50V, so hopefully they'll last a while. You'll notice they're a bit large, so some creative mounting is needed. Wayne suggested using Nichicon BPs (bi-polar caps, they're iridescent green) if you'd rather not use Silmics. C1 and C5 are the input coupling caps and should be of high quality as they're directly in the signal path. I personally used some vintage Sprague paper-in-oils, but you can likely fit some of the smaller narrow Mundorf EVO caps or Clarity Caps, either of which can be found at PartsConnexion. The lead spacing is roughly an inch.

All PCB parts populated

I hate this picture as it looks terrible from all the flux (this is before I cleaned it with some isopropyl alcohol and a toothbrush), but It shows where the film bypass caps are. The units in the audio section are polypropylene and the units in the power supply are polyester. The twisted pair is pulling off the 22V secondary for a pilot light.

WIMA film bypass caps on bottom of PCB

The chassis I selected is from IAG DIY Tube Audio Products. He lists his chassis on ebay and on his website. Hand-made in the USA and built like a tank. It would be a slightly tight fit so I needed to see where items would be mounted to the front and back of the chassis so they wouldn't bump into any parts on the inside. The IEC filter in particular needed to be offset from the center so it didn't bump into the PCB mounted transformer. I decided to mount the 0.5A fuse and socket on a blank part of the PCB so there'd be one less hole drilled in the chassis.

Lining up the chassis-mounted parts

Once everything was lined up and the holes cut, the PCB was secured in the enclosure using 1/2" standoffs. The front panel has a four pin connector in addition to a locking Neutrik TRS as most of my headphones are wired that way, so it saves me from having to use an adapter.

Wiring is scraps of Cardas I had in my wire bin, 4x24, 2x24 and 2x21 and some 24AWG, all litz in teflon. The potentiometer is the $40 100K Audionote with solder tags. It's nice and small so I didn't have to worry about it bumping into a discrete opamp. The IEC filter is from Furutech, gold plated. I normally wouldn't spend the money on it but it was discontinued and quite a bargain. RCAs are Cardas rhodium plated. The switch is a simple 3A rated toggle I picked up from Radioshack when they were clearancing everything. The LED pilot light is one from a guitar shop typically used for an effects pedal. Everything else is from the BOM.

Wiring everything up

Here's a few more images of the chassis with the wood panels.

Front of the WHAMMY amp in the chassis

Back of the WHAMMY amp in the chassis

I used a very simple circuit from ClassicValve for the LED.

Pilot light circuit to protect LED

Here's an image with the bottom panel and feet installed.

Bottom panel with vents

...and here's the WHAMMY almost done, just missing the knob.

Nearly complete

...more to come.

It's a head-scratcher why this hasn't been requested before... a switchable headphone output box. I know so many people in this hobby who have more headphones than fingers and toes, so something like this should be commonly on headphone enthusiasts desks across the world! Haha, well maybe not...

Anyway, I had a client approach me who wanted a switchbox so he could switch easily between four headphones. Obviously you don't want to have all four headphones connected at once due to various drive and impedance issues, hence the switch. In addition, the unit should be as transparent as possible as sound quality is paramount in this hobby... so we have a point-to-point 1 to 4 headphone switch, so up to four headphones can be connected simultaneously to an amp, and switching between them is as simple as the click of a switch (and swapping them on your head).

For the box I used a Hammond extruded aluminum box with aluminum endplates, anodized black (everyone likes black). It needed to be a wider model for enough panel real estate for the switch and four 1/4" connectors.

While 4 pole, 3 throw switches are as plentiful as flatulent passengers in airplanes, 3 pole, 4 throw are a little more difficult to find. I used one made in the U.S. by Electroswitch, found on Mouser. If funds permitted we would have gone with Elma/Goldpoint, but this is a great switch with smooth operation. For the 1/4", I went with the super common Neutrik NMJ6HC-S, which is the more attractive jack from their M-Series and is very reliable. It has switching ability as well, but that wasn't needed in this application.

Here's a few progress pics below:

Lining up the jacks

Drilling the pilot holes

Mounting the jacks and switch

Installing the Kilo aluminum knob

Everything was wired up using solid core silver-clad wire in PTFE. I highly recommend this wire for internal chassis work. It sounds excellent and is easy to work with. Just be sure not to be too aggressive when stripping it as if you nick the solid core wire, it can break off and you'll end up with an open circuit. You'll note below the ground is tied to the chassis via a screw and locking solder lug. This is important to ensure the metal chassis has active shielding from noise no matter which output is selected.

Interior wiring

This is a simple, effective switchbox which hopefully the client will enjoy.

Final Product

Hopefully you have fun reading this, and who knows, maybe someone will want an 8, 12 or 16 headphone switchbox in the future! You guys will be the first to know ;)

Please remember that building/modifying circuits can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings.

Back in 2004 I purchased my first serious pair of headphones, a pair of Sennheiser HD600s. This was an introduction to a number of new concepts for me: headphones that are open, benefit from an amp, are sensitive to different cables, and are intended to be listened to at home (where you could be listening to speakers, sacrilege in some circles! haha).

In these formative days of headphone audiophilea I recall being at a meet in College Park, MD where there were a number of HD600s and HD650s. We were auditioning cables by Cardas, Stefan AudioArt and other DIY concoctions including pure silver cables. It was amazing what a difference the cable could make to the signature.

I'd long since sold my HD600s and HD650s and moved on to other headphones like Audeze, when I saw Massdrop and Sennheiser teamed up to released the HD6XX. The HD6XX is quite literally a more affordably produced HD650 (based on Inner Fidelity's measurements). I figured for $200 it would be fun to have a listen to the Sennheiser house sound once again, and see how good it could sound with a balanced amp and some tweaks.

If you're not familiar with Massdrop, it's an interesting business model where the company has a number of people commit to buy a product at a discounted price. Generally there are a certain number of buyers required to make the "drop" happen, and once it does, it can take months before you have a product in your hand. The upside is you can get some incredibly good deals so long as you're patient. Massdrop also teams up with manufactures to produce one-off products at a sizable discount, such as the Focal Elex, AKG M220 Pro, HiFiMan HE-4XX and other headphones which are a little different from what's on store shelves. The Sennheiser HD6XX is such an animal.

Looking at the HD6XX versus the HD650, you'll note the HD6XX has a dark blue headband versus silver and the screen printed "Sennheiser" on the top of the band is more subtle. I personally think the HD650 color scheme is a little easier on the eyes, but given this relatively superficial difference shaves $150+ off of the street price of the HD650s and still sounds identical, the choice is a veritable no-brainer.

The stock HD6XX

Given you're saving big bucks on the HD6XX, those dollars should go toward making them even better, right? I'll be going over a few tweaks you can do for improvements in sound, comfort, and looks.

One thing I couldn't be happier about is the trend toward calfskin earpads in the past decade. Exposed foam and velour don't feel all that great against my skin. The Sennheiser HD580, 5XX, 600, 650 and 6XX all feature velour pads, but fortunately there are companies producing replacement pads. I've found the Dekoni fenestrated pads are quite comfortable while allowing breath-ability. The pads snap in place on the frame and are quick and easy to install and uninstall.

Even with the new pads, the HD6XXs look a little dull, easily glanced over when looking at newer headphone designs with chrome and carbon fiber. I decided to reach out to Larry at Headphile to see about getting some custom wood cups.

Talking about Headphile with some of the old-heads at HeadFi will elicit smiles and good memories. Larry's been at it for quite some time, and for a little while there, the "Darth Beyers", which were Beyerdynamic DT770 headphones modified with wood cups, were one of the most popular cans on HeadFi. Every now and then you'll see a pair pop up for sale, and if you like bass, I'd recommend you give 'em a shot. In addition, if you have the scratch, Larry is still building them with a number of wood choices... although I don't know if he's still building the deep versions (which I most favored).

I chose Padauk (pronounced Pah-duke) wood as it's reasonably priced and has a nice reddish hue, which will pop on the dark HD6XX. Larry offers the cups open with screens or closed. The open versions sound pretty much identical to the stock screens with perhaps a tiny bit more reverb, and the closed versions have notably more reverberations (or a chamber-like effect) depending on what sort of damping is applied inside.

The installation process is quick and painless. The screens are pressure fit on the frame, and using a spoon or similar utensil (I used an avocado knife) you can slowly pull the screen away from the frame and remove it.

The screens can be removed easily with a spoon (or avocado knife)

The difference in color and presentation is night and day from the new wood cups and the existing stock screens.

Headphile wood cups versus stock screens

Installation is completed on each side using a set of 4 brass wood screws.

You will need to adjust the tension of each screw to ensure it has adequately threaded into the wood, but is not impeding on the cavity for the cable plug insert, otherwise the cable will either not insert at all or will be super tight.

The HD650 (and HD6XX) is a warm-sounding headphone, no doubt about it. It can be a little too warm and rolled-off in the highs for some. This is where a cable comes into play. I opted to build a Zynsonix Xev cable for the HD6XX. While the most affordable in the line, it features silver-clad conductors, low-strand count and a PTFE (Teflon) dielectric, giving it a forward and detailed sound signature. It's exactly what the HD6XX needs, pushing forward the treble, resolving the bass, and giving the headphones a far more dynamic presentation.

I wasn't sure if I would keep the HD6XX, it was more of an entertaining experiment, however with these mods the enhanced comfort and sound really make it a winner and a definite keeper. Headphone enthusiasts these days are quite lucky, as it would be very hard to reach this level of sonic performance at this price years ago.

If you'd like a Xev cable made to your specifications (whatever length, sleeving, and termination you'd like), please reach out to Zynsonix today and take your Sennheisers to the next level.

Zynsonix Audio, LLC does not have any relationship or financial interest in the companies mentioned in this post, including Headphile, Massdrop, Sennheiser, Inner Fidelity, Dekoni, etc.

Another day, another headphone amp :) One of my life's pleasures is digging around on eBay for exciting finds, whether it be obscure vintage tube equipment or interesting/useful PCBs. This article covers the latter, a very nicely made PCB which features an octal (8-pin) tube OTL headphone amp circuit. Specifically, this is an Aikido input with a White Cathode Follower output, based on John Broskie's design. The circuit is designed to power most headphones, including those with a 32 ohm impedance. This is relatively uncommon with OTL headphone amps, which usually get along best with headphones ~300 ohms.

Top and Bottom of PCB

The tube compliment is a pair of 6BX7 or 6BL7 output tubes, a pair of 6SN7 input tubes, and a 5AR4 rectifier... because tube rectifiers are fashionably old school. Using all these tubes requires a hefty transformer, the 8.6lb.Hammond 272JX, which has a 5V, 6.3V and 600V secondary outputs. Yes, 600V, so this is not an amp for beginners.

One can utilize the 6BX7 or 6BL7 tubes by switching two pairs of jumpers on the board, or the circuit can be configured to only work with one of the two tubes, but you can select between 32 and 300 ohm outputs using the jumpers. I personally chose the 6BL7 tubes and two different impedance outputs.

One nice thing is that getting pairs of vintage 6BX7 / 6BL7 tubes is pretty reasonable ... $25-30 a pair for many different brands and vintages. Same for the 6SN7. You can get the GTB variants which are built to a slightly higher spec. For the 5AR4 you'd probably want to get new construction from Sovtek or similar. Guitar center is a good source.

All the stuff on the BOM is of great quality: WIMA film caps, Vishay resistors, Nichicon electrolytics... all the good stuff. I ended up digging around the workroom to see what I had first... mostly Kiwame and carbon comp resistors, hand matched as carbon comp values can vary by 10% or more. Film caps are compact Panasonics. For the power resistors I think I went with Koa Speers as the Vishays were oddly overpriced on Mouser.

PCB populated with the smaller components

Ceramic tube sockets soldered in place

For the larger film caps, I wanted to incorporate some of the EVO oil Mundorfs. The sizing is tough, as the Mundorfs are fairly compact, but wide, and the chassis is about 3" tall, so some unique fitting was required. As most of the area underneath the caps on the circuit board doesn't have any traces running through it, I used a cutting disc and Dremeled away the area on each side... this would give an extra 1/4" to 1/2" height lost from the PCB and standoffs for extra clearance. I drilled a hole on each side of the PCB as well so a zip tie could hold each cap in place.

The chassis I selected is from IAG DIY Tube Audio Products. He lists his chassis on ebay and on his website. Hand-made in the USA and built like a tank. The chassis gauge is relatively thick, but aluminum so easy to work with. I chose to cover up the pretty polished aluminum with painters tape to try and prevent any scratches.

Using a step drill bit to make holes in chassis

Using a Greelee punch to make the holes for the headphone outputs

Dremelled out area for IEC power inlet

I accidentally inverted the drawing when punching the holes, so we have an extra hole here. No big deal, it can be covered with a 1 1/8" Hillman hole cover.

Interior of the chassis

The populated PCB slips right in place. There aren't too many wire connections needed, just the transformers, pot controlled RCA input, and headphone output. Shielded Cardas 2 x 21.5 was used for the input and output (as they no longer make the 2 x 24 for some reason). I also wired up a pilot light to the 6.3V heater. The Hammond comes with a 115V and 125V primary. Typically you use the one that closest matches your house's voltage. As mine is 120V on the dot, I used the 125V as it didn't really matter. You dial in the voltage via the two adjustable resistors inside anyway.

When adjusting the 300V secondary, I noticed R24 was dissipating a bit too much heat and starting to smoke. Per the seller, R24 has been changed to 22K, so I went ahead and swapped that out.

By default for a tube amp, I wired in a filtered IEC outlet, however these are incompatible with this design as there is a ground isolation circuit built in. Once everything was corrected, I ensured the secondaries were dialed in correctly, but was getting a high DC offset.

To be continued!

Looking for sale or to save a few bucks on audiophile headphones? Whether you’re just getting into personal hifi listening or you’ve been the hobby for a while, you’ve likely noticed that it can get expensive, quick. Over the past several years, we’ve seen a huge uptick in manufacturers retail prices, with many headphones stretching into the several thousand-dollar price range. From the $55,000 Sennheiser Orpheus to the $18,000 HiFiMan Shangri-La, prices can be staggering.

The Sennheiser Orpheus. I'll take two please! :)

Even at real-world prices From the cans to amplifiers to cables to pads, everything will put a dent in the ‘ol wallet. As such, I wanted to put together some tips and tricks I've learned over the years to ensure you are getting the best sound for the money and don’t end up taking a bath because you end up with a new set of cans you don’t like.

Get to a Local Meet or Show
One great way to save money is not buying headphones that don’t fit your tastes. The best way to audition headphones before you buy them is at a meet, whether it be HeadFi gathering, or a local audio show. Many audio shows now have rooms for high end headphone listening (this wasn’t commonplace 10+ years ago), so you can quickly sample a number of different headphones quickly without someone trying desperately to sell you something for a commission. Auditioning headphones saves a lot of time, cost and effort versus buying blindly or based on online reviews. Everyone has different ears and different preferences, and you should trust your own ears when it comes to the sound you prefer. Reviews have their place, but one person’s “high-end sparkle” is another person’s “bright and sibilant”.

Find local HeadFi meets here.

A photo of Head-Fest from Stereophile.com

Black Friday / Cyber Monday
While there are a lot of over-hyped sales on BF/CM, it’s often the best time to purchase high-end headphones. Manufacturers like Audeze and HiFiMan have incredible deals directly on their site where you can save up to 50% in some cases. Just remember to watch the sites carefully and refresh often, as they sell out quick. Also be sure to keep an eye on BuyDig, Adorama, Monoprice and Amazon, as they often have great deals on brands like Fostex, HiFiMan, Audeze, iFi Audio, Beyerdynamic, Sennheiser and others.

Keep a close eye on Audeze.com near Black Friday

Slickdeals
Slickdeals is a great place to find deals on videogames, electronics, clothing, food, you name it. The curators there do a great job of finding headphone deals, generally from BuyDig, Adorama, Newegg, Monoprice, and the manufacturer’s websites. Simply run a search for “headphones” at the top of the page and sort by your budget on the left to see the deals listed in chronological order.

HeadFi Deals Page
Having a subscription to the HeadFi Deals Page is a great way to get email notifications when there is a deal. I try to participate there regularly and there are many others monitoring email blasts from various manufacturers. Generally there are several updates daily.

For Sale in the Forums
Buying headphones new for full price is a great way to lose money. Depending on the headphone brand, model, condition, availability and other factors, a used headphone will generally sell for 50-80% of its value. If it’s barely used with accessories and proof of purchase, this is on the higher end, and if it’s a couple of years old in very good to excellent condition and the manufacturer is more prone to running promotions on the product, 50% is pretty common. Some headphones, like MrSpeakers, hold their value better as the manufacturer doesn’t run heavy product sales/promotions, whereas headphones like Audeze or HiFiMan, which are often discounted, don’t hold their value as well.

Thus, if you anticipate selling your headphones after a couple of years of ownership to upgrade / side-step, etc., I encourage you to purchase used on the forums. That way the difference between your buying and selling price will be far less than if you purchased new. Active headphone communities include HeadFi, Head-Case, Super Best Audio Friends, and others. A good way to search others is HiFi Shark. Each forum has it's own rules (and culture), so it's important to review these before posting anything for sale.

Please note that you must use your best judgment when purchasing on the forums, ensure the seller has a clean history and good feedback, don't ever use "Paypal Gift", and you can request the seller take a new photo of the item being sold with their screen name in it to ensure they actually have it in their possession. Using a credit card via Paypal or other method offers you protection from the credit card company if you do not receive the item or it is not as described. My personal experiences with Paypal buyer protection have been poor, so using a credit card provides an adequate layer of security.

MassDrop
If you plan on purchasing a new headphone and holding on to it, MassDrop has some great deals on headphones that are only available through the platform. Interesting offerings like the Focal Elex (a cross between the Elear and Clear), the Sennheiser HD6XX (a rebadged HD650) and HD58X Jubilee, the AKG K7XX, the HiFiMan HE-4XX, the Fostex TH-X00, the Koss Porta Pro X, Fostex T-X0, and many others have been released that are a tremendous value. Every headphone that I have tried provides incredible bang for the buck in terms of sound quality for the dollar compared to normal headphones being offered at street prices or MSRP. I actually picked up the HD6XX recently and did a few tweaks.

The Sennheiser x Massdrop HD6XX is a screamin' good deal

If you want an even higher value and don’t mind buying used or B-stock, getting Massdrop headphones used via forum or via eBay resellers (use a 15% Ebay coupon if available) probably represents one of the best headphone values on the market today.

Ebay 15% Off Coupons
I’m not sure how long eBay will be offering these 15% off coupons, but they’re a real boon for anyone planning a larger purchase for a pair of headphones, amps, etc. With a max discount typically at $100, it’s a great way to trim down the price of new, used or b-stock gear. If you know a 15% off coupon is coming, sometimes it pays off to make the seller an offer lower than their Buy It Now price, then once the offer or counter-offer is accepted, stack the coupon on top. Just make sure to get the timing right.

Before you purchase any used gear, be sure to check the Forums and/or HiFi Shark. Sometimes gear costs less on the forums even after the eBay 15% off, as sellers have to build the fees into their asking price.

Email Subscriptions
Many retailers have strict reseller agreements that don’t allow them to publish prices for gear under the MSRP unless there is a company approved promotion. While this is generally always true on retailer websites, often times you’ll see lower prices via email blasts as it’s a limited distribution and the retailer has less of a chance to have their hand slapped. So go ahead and get on that spam list if you want to ensure you’re getting the best prices.

Call on the Phone
Most of the gear in the audio industry that is being resold by secondary retailers has a heavy markup. If a headphone costs $999 on a retailer’s website, the cost to the retailer was probably $500-600. Granted the retailers have many expenses including personnel and numerous business costs, but there is often times a little bit of wiggle room if you give a call. Requesting 10% off generally works and the salesperson will be happy to get the commission.

This doesn’t work as well for direct sellers as the price-to-cost ratio is a little different (there’s likely less markup).

Old Favorites
While they may not be the flavor of the month on the headphone forums or the featured article in The Absolute Sound, there are some older headphones that represent great values. Currently, because of all the competition in the space, these headphones are even cheaper than they were years ago. Check out old favorites like the Beyerdynamic DT770, DT880, DT990, as well as the AKG 240S. Often sites like Buydig have these for sale dirt cheap and they're built to last many years.

That about wraps it up. These are little tips I've learned over the past 15 or so years I've been in the hobby, so I hope it helps a couple of you. I’m sure I've missed a few things, so please feel free to add them in the comments.

Flash back to mid-2017 and you may remember the super cool "NuHybrid" Headphone Amp that Pete Millett designed around the Korg NuTube. If you're not already familiar with the NuTube, the current model is called the 6P1, which is a thoroughly-modern, dual, very low power, directly-heated triode tube. The NuHybrid used the 6P1 as a driver tube for a desktop headphone amp with very good results.

Back to October 2018, Korg has not been resting on its laurels, and has released a couple of cool new DIY designs. Both make a lot of sense given the low power requirements of the NuTube: a portable headphone amp and a guitar pedal. Some of you may say "wait a minute! the NuHybrid was sensitive to vibration, I can't imagine it bumping around in your pocket or getting stomped on during a performance". I was thinking the exact same thing, however I'm pleased to note that Korg has completely eliminated this concern in the new portable headphone amp (the HA-K1) by mounting the Nutube off the main board and using a modicum of foam to dampen things.

Being the ravenous DIYer that I am, Pete was kind enough to send me an HA-K1 to play with. Included in a relatively non-descript box are the instructions in Japanese and English, several baggies with parts, the enclosure, a sticker, and a PCB which is semi-populated with SMD parts. This is similar to Elekit's portables that knock out some of the steps. I personally don't mind as I don't enjoy futzing with teeny tiny SMD resistors.

Pre-populated PCB bottom

Pre-populated PCB top

The case resembles an Altoids mint tin case in both size and material, which is commonly the enclosure choice for a CMoy. The top is a dark piece of translucent acrylic which has the labels for the controls printed on it. In the parts baggies are a variety of Nichicon caps, trim pots, standoffs, switches, a smaller PCB for the NuTube to mount on, and a couple of op-amps.

The HA-K1 kit parts

The tin case and acrylic top

The instructions discuss the order in which the PCB is populated, and refer to a numbered bill of materials. There was an instance that I wasn't quite sure what the BoM was referring to e.g. "connector", but since there are so few parts to worry about it's pretty easy to just visually check the board and confirm. A couple of the parts need to be visually distinguished, like the codes on the side of the different value trim pots, and the solder eyelets are a little on the small size and close together, but there is nothing particularly difficult about the build.

I would recommend having at least decent solder skills or plan to use some extra flux to ensure you don't bridge any eyelets accidentally. I also found myself using a solder sucker a little bit to tidy up the joints, but I'm more OCD than most ;) The entire build took about an hour and a half, and I like to take my time.

I also needed to whip up a short mini to mini cable as surprisingly I did not have a spare.

3.5mm mini to mini cable

Once the build is complete, there are a host of fun little things to tweak like the internal gain, the load on the anodes, a bass boost switch, and choosing which op-amp you prefer. I found that I liked the load on the anode a little over halfway and the volume a little under halfway turned. I tried both op amps, liking the basic JRC for alternative rock with more electric guitars (overdriven guitar sounds more raw) and the Muses 01 for the indie rock I prefer which is more electronic and vocal based (smoother, more balanced presentation). The bass boost I liked better for poorly recorded rock that lacked body, but was a little aggressive with already bassy music.

Bottom of amp with stick-on footers

Top of completed unit

So bottom line, is this piece of kit worth your time? If you enjoy tube sound and want it on the go, I'd say definitely. Overall the sound is very full and engaging, warm, dynamic and non fatiguing, just the way I like it. It's a little more lush than amps like the Chord Mojo and iFi xDSD. It is also probably the lowest cost portable tube amp on the market that is properly implemented and doesn't suffer from any microphonics what-so-ever.

If Korg releases a future (or alternative) model, I'd like to see a built in USB DAC so we can bypass the phone's internal amp, but for the price and the sound, it's a good value.

Pros

Fantastic sound, warm and engaging
Nice portable size and attractive case
Good quality internal parts
Sound is highly configurable to user taste
Well-designed PCB screen print eliminates confusion
Quick and easy to build

Cons

No built-in DAC model yet
Requires at least decent soldering skills
Bass boost adjustment requires opening amp
Tin case prone to dings

I'm of the understanding that the only American distributor at the moment is Pete Millett, and they are available via this eBay page. For full disclosure, I have no business affiliation with Korg or Pete Millett. The review sample was provided to me for evaluation / review purposes.

The Fine Print: Please remember that building/modifying circuits can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself and/or your surroundings.

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