DIYAudio WHAMMY

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The acronym DIY stands for Do It Yourself, and that’s what she said… The forum diyaudio.com is for this community what Head-Fi is for headphone enthusiasts. It’s an international institution of which I’ve been a proud member since 2011. Boy, it’s been some time, huh?
The forum touches on everything related to DIY: amplifiers, DACs, ADCs, speakers, headphones, tubes, solid-state, and class D. Whatever you like, it’s there. But a community is nothing without people. Besides enthusiasts from all over the world, you can spot the best audio engineers just chilling and giving tips around. Incredibly, you can approach one of the big names, and they will gladly help within their respective fields of interest.
The biggest celebrities of the forum are Nelson Pass, tenderly nicknamed Papa and the “Wizards Assistant” himself, Wayne Colburn. Those names can and should ring a bell. They are the masterminds behind the Pass Labs – California, USA-based manufacturer of Hi-End amplifiers. More importantly, they are both incredibly nice and down-to-earth.
They openly share some of their discontinued products to the community, supporting the builders. There is a community around those projects, and I cannot skip user 6L6, Jim, who creates the most amazing, thorough, step-by-step build guides for Papa’s projects. Since we have all the main characters on the stage, we can proceed to the subject.
Reviewed WHAMMY is a headphone amplifier project presented by Wayne Colburn at the forum’s official festival, The Burning Amp. I remember reading about it on the forum. I got really excited, especially since I had just got Audeze LCD-2F. There was an international group buy, and I managed the whole order for Poland, including shipping from the US and domestically. Mr. Colburn was so nice that for handling almost 20 orders, he dropped me a set of Toshiba MOSFETs for this project. Once again, super nice man.
Yes, I have built this amplifier once. Sadly, I had to sell it with the headphones for financial reasons. Meaning I was broke. The memories of that set are still with me, though. Great sound, is simple to assemble and is fun to use. Recently I have started grumbling about having some DIY on Ear-Fidelity.
Finally, Paweł commented with this line: “just don’t f*ck it up”. I won’t. I sent an email to the DIYAudio Store and contacted Jason Donald, the owner of the forum and the respective store. It was an incredibly pleasant conversation, especially since he is our reader already! Cheers, Jason! Few emails later and some mingling with customs, the package was in my hands.

Build and Tech of Whammy​

I’m not going into a piece-by-piece detail here. If you are interested in that, visit the official thread on the forum. WHAMMY is an opamp-based circuit. The opamp gives the voltage gain and controls the feedback loop. It is followed by a push-pull, complimentary MOSFET source follower. It is biased in class A/AB between 27 mA to 60 mA (or any other value, if you are smart enough to not blow it up). Greedy boyz always want more current.
The bias spreader is an unusual arrangement of an optocoupler controlling the voltage on the source (bias) resistors. The stock opamp is a low noise JRC4580DD, and MOSFETs are Vishay’s IRF610/9610. The original WHAMMY used the unobtanium Toshiba 2SK2013/2SJ313. The power supply consists of a 25VA Talema impregnated transformer, a CRC filtering, and the staple of electronics: 78XX/79XX voltage regulators with LED lifted references.
The power supply is very stable and has negligible noise. I need to point out one thing, there is no output protection. Depending on your opamp and the exact output voltages of the power supply, there will be a thump when powering on, and there is no protection to your precious cans if something goes horribly wrong (DC on output). If you wish to be safe, either a DC blocking capacitor (10kuF/35V) or a speaker protection system can be installed between the amp’s output and the output jack.

The choice of parts surprised me. While $300 is not super affordable for a headamp, the parts included in the set are all premium! Dale military grade RN55 resistors, Panasonic, Elna, Nichicon caps, and Alps potentiometer. Audio connectors are made by Neutrik, and the AC inlet is a big unit with fusing and filtering. Also, some Mogami 2552 shielded twisted pair cables. It’s all excellent choices, and honestly, better quality than I was expecting at this price. $300 is a price including the enclosure. You only need some tools and time.
Oh, it will not drive the F4. It doesn’t have enough output voltage (although you might be able to modify it so…).
TLR
Buffered opamp, class A, MOSFET output stage, linear power supply. Premium parts include big brands like ALPS, Elna, Dale. For $299 you get (almost) all parts that you might need.

Assembly​

You need some tools for this. Luckily for you, they are all specified in the guide. The project comes with a comprehensive, step-by-step build guide by the 6L6. I’m an experienced builder, as I worked in electronics assembly and built some projects on my own, including the massive First Watt F5Tv2.
Assembly took me one evening. A less experienced builder will need 2 or 3 evenings. It all worked with no issues from the first try. If you wish to attempt this project, you should be at least proficient in soldering and have a basic understanding of electronics. The guide should have included one point: the power LED. It is not specified on the PCB. Also, the current limiting resistor was not included in the set. I have easily found a suitable one (20k, I think) and attached the LED circuit to the C9’s pins.
One hack I recommend to all builders is installing the C3/4 on the bottom side of the PCB. It will make your life easier if you want to run discrete opamps because their size interferes with the big caps next to the sockets. Recently I met a person on a Facebook group who bought this set but couldn’t make it work. He pointed out that the input ground pad on the PCB is not described, which led him to a mistake in wiring. Hopefully, we will get his piece to run soon.
Update: he did and is super happy with it. Way to go, Jay! Assembly is pretty straightforward, but I recommend having some experience before attempting it yourself. It is an intermediate project.

Finished Amplifier​

The included chassis is made out of steel and aluminium plates. It’s all cut on a CNC machine and fits perfectly. The sides of the top and bottom plates could use better machining, which is my only complaint.
The front panel is a thick cut of aluminium with printed descriptions all over it. The back plate has descriptions too. After assembly, it looks like a commercially available product. It looks very respectable on the table and doesn’t get too hot.
I like its aesthetics, especially small accents like silver knob and red nut for a 6,3mm jack. They give it some visual character. The only real downside to the reviewed WHAMMY that I can see is a very high gain. It can be impractical in most cases. See the mods section for solutions.

Sound of WHAMMY​

I have built the amplifier with all stock options, as I want this review to focus on what you get from the box. There is an insane amount of mods and changes to be done, so it is essential to get some reference for what a new owner can expect from a vanilla WHAMMY.
My exact config is LED references in power supplies, JRC4580DD, and stock parts. Let’s start with first impressions. This amp is absolutely amazing. It sounds like a good class A amplifier like Accuphase (who also use JRC opamps…), or obviously, Pass Labs. Sound is tuned for pleasure, smooth, dynamic, colorful, and realistic. It has a slight tone to it, a touch of warmth and a bit of meat on the bone. Call it as you want. It sounds inviting, but after a long day at work, when you just want to listen to music, you will want to use WHAMMY. On your day off, you also probably want to use it. It is a great blend of just right in every category. You will find amplifiers better at something, but it is rare to find one that is a true jack of all trades.
Bass
The bass feels slightly elevated like there is this muscular quality to it. As a bass head, I’m more than happy with that. It doesn’t influence the midrange, so no worries. Or maybe other amps I have tried can’t produce that punch and volume? While this range might not be as precise and tight as other amps can reproduce, WHAMMY has this wonderful ability to make it seem more real.
That works with both natural drums and synthetic bass. Take a listen to already beaten-to-death Earth Drums by He Xiun-Tan. I swear every audio show has to play this. But it is a great reference for bass. WHAMMY made me almost feel the air moving. If you like big, bold bass with nice slam, that still gives you more resolution than you might need, this might be it.
Midrange
You know what’s coming. Class A amplifiers are famous for their reproduction of voices. While the whole amp is not biased in class A (the opamp isn’t), we still get the flavor of this kind of amplification. Once again, WHAMMY has this intense, emotion-packed, realistic sound. Midrange is a bit on the closer side, but the volume and detail make it feel very natural. I don’t like this adjective, but it is really organic.
It could be the slight imperfections that make it feel more real. I know amps that can retrieve more info, yet it doesn’t have the same impact. If you want to understand my point, a trip to Pulp Fiction’s OST, especially the Son of a preacher man, by Dusty Springfield. Her voice feels colorful, beautiful, and simply stunning. Just.. normal. The natural dynamics and the tonality are top-notch. All of the vocals separated perfectly and were easy to pick up on their own, with no effort. Top performance, here.

Treble
As WHAMMY is a coherently sounding amp, treble features similar characteristics to the rest of the ranges mentioned earlier. Highs are enthusiastic and full of energy. They have a hint of warmth, perhaps the biggest of all. It is really up my alley. Cymbals, bells and whistles sound very realistic, natural and straight-up fun. What I really appreciate in WHAMMY is that it never ventures into “too much” region.
For example, the Main Title from Star Wars IV: A New Hope played by a whole orchestra, can easily get overwhelming, especially when amplifiers lack speed or headroom. None of that happens here. Brass instruments sound like brass, bells like bells, etc. Even in the most intense moments, you can easily pick up a melody played on each of them. It is like listening to the orchestra live in a sense. Is it the most transparent sound? No. Is it engaging and makes your foot tap? Hell yeah.
Soundstage
Reviewed WHAMMY doesn’t have the widest or deepest soundstage on the market, but the coherency sets it apart from the competition. Sometimes the soundstage feels uneven as sounds in the middle sound less precisely positioned than those more to the sides. Here it is all smooth, which makes a world of difference in transitions. An example is Aesthetics of hate by Machine Head where the drums are set up wide in stereo, and you can hear that with WHAMMY. Everything sounds similar and in the same plane. The width and depth are in the middle of the scale, as mentioned earlier, you can get bigger presentation from other amps. For me, what we get is perfectly satisfying.

Pairing​

HiFiMAN HE-6SE

Oh my God yes. WHAMMY is absolutely spot on here. It is powerful, it gives the famously hard-to-drive cans a run for their money. Half of the scale, and we are good. The extreme resolution and control of those headphones work fantastic with the warmth and organic sound of WHAMMY.
This might be the cheapest way into TOTL sound if you ask me. This sound has everything you might want: good sound staging, insane resolution, beautiful tonality and a nice slam in the bass. This was my most used headphone in this review.
Sennheiser HD800
Another great combo, the high impedance of the German cans was not a problem for the WHAMMY. This amp added nice mass to the sound, and while it is not a champion of sound staging, it certainly didn’t kill the strongest point of the HD800.
With their relaxed sound, light, open construction, and WHAMMY’s unproblematic sound, it was a great combo for games or long hours in front of a computer.
HiFiMAN Sundara Closed

This combo is for those looking for something on the other side of the scale. This can have a darker sound when compared to those mentioned earlier. Also, as a closed construction, it delivers strong, punchy bass. The midrange and treble are still great, but the soundstage is pretty closed of in this combo.
On the other hand, relative to the price nothing to complain. Detail, famous HiFiMan’s resolution, and bouncy lows might be up your alley. Recommended.

Comparisons​

iFi Audio iDSD PRO Signature
The integrated amp in this combo is nothing to laugh at. Class A output stage, switchable tube circuit, balanced and single-ended outputs. The biggest advantage the iFi has is the size and precision of the soundstage. WHAMMY, on the other hand, sounds much more natural, with nicer tonality and a smoother sound. iDSD PRO Signature was the main source in my comparisons.
Topping A30 Pro
This might be one of the most popular headamps from Topping. Great output power, XLR and 6,3mm outputs, and selectable gain. This company is a powerhouse in the features department. Soundwise, A30 PRO offered more detail, really pushing the nuances to the front. While not as detailed, Whammy was much more coherent, realistic, and pleasurable to listen to.

Opamp rolling​

This would only be a DIY review with mods. I mean, if you built an amp, why not push it further? An obvious and easiest mod is opamp rolling. Take the stock JRC out and pop a Burr-Brown, Muses, Linear, or whatever your heart pleases. I bet you have a whole drawer full of them. Please ensure that the opamp you want to use is a dual part that handles up to +/-18V power supplies. If you want to push it further, get some discrete opamps. They really allow us to get the most out of WHAMMY. I have tried 2 of them, and here is a short summary for you:
MuzgAudio
This JFET input opamp is manufactured by a polish company that started as a DIY startup. It is extremely small, and the size was located in height. A trim pot is available if you wish to trim the output offset to an absolute minimum. Stock it gives me offset in the range of 1mV, so a great result (JRC4580DD has 6-7mV). The sound signature of this opamp is neutral. It is the most universal out of the bunch. It gives a reasonable improvement to all of the qualities mentioned earlier. If you want WHAMMY, but better, this might be it.
Stacatto Audio
This one got me by surprise. It is an opamp with a JFET input and output. The output stage is also single-ended. It is finely tuned to an offset in the range of 1mV, similar to the MuzgAudio. There is a trim pot available. Sound-wise, it has a strong old-school, tube-like sound. It is warm and thick and has this effortless openness. This might be it if you want a tube-like sound without dealing with expensive and noisy parts. Oh, while doing that, it still delivers great dynamics and resolution.

Mods​

Let’s get into more advanced mods. One recommendation is to add 100nF decoupling capacitors close to the opamp socket, in parallel with the C3/4. They will help when rolling high-speed opamps, as they might go into oscillation without extra decoupling. The rest is pretty simple.
Most people should start with different coupling capacitors at the input. You might want to change the gain, by changing the feedback resistors. There is an option for a capacitor in the feedback circuit, marked Cx. It will also improve the stability margins.
Calculate it for a corner frequency of around 200kHz, and you will be good. Please use good quality parts like a styroflex or foil caps here. The feedback network is susceptible to parts quality.

As a Preamp​

I recently borrowed a Schiit Audio Gjallarhorn from a friend (thanks, Grzesiek). They worked together so well. It is a desktop power amplifier, making it a perfect candidate to test the pre-out of the WHAMMY. WHAMMY can drive it super easy, and thanks to the swappable opamps, I could mix and match the sound signatures to get the best pairing. Thanks to a big headroom, WHAMMY will easily drive the most power amps on the market.

Whammy review – Summary​

It might be my passion speaking, but WHAMMY is an outstanding amplifier. One that you can make yourself, on top of that.
While it lacks balanced outputs and other fancy features, it focuses its value on the sound. And it is great. Natural, powerful, organic, and easy to listen to, with nice detail and sound staging. It was able to handle flagship headphones like they were nothing. This is no ordinary amplifier. Let me tell you that.
On top of that, you can improve it further by rolling opamps, and modding. Wayne Colburn, the amp designer, has put all of his experience into this deceptively banal design. It truly is an example of more than just a sum of its parts. The only sensible thing is wholeheartedly recommending WHAMMY to everybody who can handle a soldering iron. In the end, it is Wayne’s Headphone Amplifier Must Make Yourself!
Highly Recommended.


Big thanks to DIYAudio for providing the Whammy for this review. I wasn’t paid or asked to say anything good or bad about this product, all of the above is just my personal, unbiased opinion.

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