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WHAMMY DIY Build

JMAudio

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I have the WHAMMY Class A heaphone amp and with the ability to swap op amps out - I have the OPA627, LM833N, OPA2107AP - my favorite is the OPA627 by far- LM833N is warm tube like sound, OPA2107AP is more detailed still and the 627 is like opening up a window surpassing any op amp I ever heard. I wonder if someone here could measure the WHAMMY ?
 

JeffS7444

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I have the WHAMMY Class A heaphone amp and with the ability to swap op amps out - I have the OPA627, LM833N, OPA2107AP - my favorite is the OPA627 by far- LM833N is warm tube like sound, OPA2107AP is more detailed still and the 627 is like opening up a window surpassing any op amp I ever heard. I wonder if someone here could measure the WHAMMY ?

:facepalm: <- my feeling about using $28 opamps as "upgrade" to $0.71 stock part which already works well: Basic measurements at bottom of this page:
https://guides.diyaudio.com/Guide/WHAMMY+headphone+amplifier/3?lang=en
Very likely yours will measure much worse, and no I'm not being sarcastic.
 

JMAudio

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:facepalm: <- my feeling about using $28 opamps as "upgrade" to $0.71 stock part which already works well: Basic measurements at bottom of this page:
https://guides.diyaudio.com/Guide/WHAMMY+headphone+amplifier/3?lang=en
Very likely yours will measure much worse, and no I'm not being sarcastic.
Sound wise they do make a huge difference- not sure if you ever tried listening for the difference but I was astonished at how much more engaging and revealing the sound became. If you never tried it how can you comment? What do I have to gain by experimenting- even Wayne Colburn said they will make a difference in sound quality and what do you know they do!
 
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JeffS7444

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Sorry, didn't mean to come across as a jerk about it, but as soon as I realized that was a high-speed opamp you were using to replace an audio opamp, red lights started flashing, because while those sorts of devices can be perfectly OK for use in audio applications, they're not generally plug-n-play, and this is no exception, and I suspect the differences you are hearing are due to oscillation which might make things like female vocals and violins sound more "exciting" but likely if you could see what square wave response is, you'd see a lot of ringing.

Optional parts C7 and C2 on your WHAMMY board: What did you use there? Those are feedback loop high-frequency response compensation capacitors, and off the top of my head I don't know how to calculate appropriate value for OPA627, but perhaps someone else here does.

Also note page 25 of TI datasheet:
http://www.ti.com/lit/ds/symlink/op...ll-mousermode-df-pf-null-wwe&ts=1590346858787
Which indicates that you really want high frequency bypass capacitors on power supply lines located as close as possible to the device (stock circuit has none), and really want to relocate other key parts as close to the opamp as possible. This is why using high speed opamps to replace audio opamps can be tricky. And once you do optimize the circuit, you will find it no longer sounds much different from stock.
 

Martigane

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I've also build a WHAMMY a year ago (already!), and I tried different Op Amps.

I performed measurements with scope and APX555 with each Op Amps, and got some interesting results.
First observation is that different Op Amps give both different subjective and objective results (meaning the rest of the system is good enough to highlight Op Amp limitation).
I also compared the Whammy to the JDS Atom, and, well, the Atom is now on a shelf :)

I have never had to use C2/C7 to prevent oscillation, it was a non issue even with fast Op Amps tried. (max 40V/us if I remember).
That being said, I indeed made a proper local decoupling for the Op Amp with metal film capacitors.

From experience I know that a complete system/circuit is more complex than just a number/curve, there are a lot more dimensions needed to fully characterize a system: as of today, we can't claim that we fully understand the behavior of such system and have it 100% characterized/measured.
So no, I'll not be satisfied with just " below threshold of audibility for XXX measurement" , and instead I will perform blind tests and more specific measurements and dive looking for differences that would explain what I hear... That's the fun part :)
Objectivist and Subjectivist should not always be exclusive... but I understand that it's just easier to pick a side and hold your beliefs there..

For fun, I zoomed (a lot) in the transients of a 10kHz square wave and saw different behavior across Op Amps, and created a GIF for each Op Amps.
See this post on diyaudio: #2324
Now, I did not say it directly translate to subjective observations, but it's worth checking if there are correlations..
 

JMAudio

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So opa627 results from my ear are best as mentioned before but vs actual results much better than opa2107 but how were the measured results ?
 

Martigane

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I did not try/measure the OPA627, only the OPA2107. I could give it a try someday, but right now I'm very happy with my system synergy.

OPA2107 measured reasonably well, but not the best.
Here it is at 8Vpeak output, 1kHz, 160Ohms load.
THD N 1K Right 8k.png


As for the global comparison, this is what I have: (notice, it's only THD, not THD+N)
THD+N = f Hz ALL ROUND1 OP AMPS real zoomed2.png



It was interesting to note that while the Burson V6 vivid had the worse distortion raise as signal increased, its noise did not move much, while other Op Amps produced residual wideband noise as the output increased.
The amp outputs 10Vrms before clipping, and I typically listen with a <1V peak output; so listenning window is below the 250mV xAxis's THD+N below:

THD+N = f Hz ALL ROUND1 OP AMPS V2.png
 
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JMAudio

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The amp builder I bought my whammy from tried the Burson v6 and said he preferred the opa2106 and the opa627 best
I confirm my option on opa2107 vs opa627 as the best overall sound presentation with the opa627 as my win for opa rolling
 

Aperiodic

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I would consider building this if only there was a full kit- meaning a pre-drilled and cut chassis, with all parts and shielded cable- just mount everything and connect it up. Just like the old Dynaco days. I can build the pcb. Since there is no full kit almost three years after it first appeared on diyaudio, I guess it's full-on diy for anyone who wants this. I was also thinking it would look good 'open' á la the Botthehead amps but I don't have woodworking skills or tools either. Once 'fabbing' becomes involved, it moves from 'fun project' to 'actual work' for me.

Also I use sensitive IEMs a lot and my agdr-modified O2 is dead quiet at any volume stting with either the IEMs or my 250Ω Beyers. If this had switchable gain (I can barely use my volume control on my IEMs at a 3.4x 'Hi' gain), I can't imagine that would improve with the 4.7x fixed gain of this amp. It does look like a fun build if you don't mind all the mechanical work being 100% DIY.
 

sngreen

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I have the WHAMMY Class A heaphone amp and with the ability to swap op amps out - I have the OPA627, LM833N, OPA2107AP - my favorite is the OPA627 by far- LM833N is warm tube like sound, OPA2107AP is more detailed still and the 627 is like opening up a window surpassing any op amp I ever heard. I wonder if someone here could measure the WHAMMY ?

Are pins between OPA627 and OPA2107AP compatible, how did it work?
 

trl

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https://www.ti.com/lit/ds/symlink/opa627.pdf vs. https://www.ti.com/lit/ds/symlink/opa2107.pdf.

OPA2107
OPA2107.jpg


OPA627
OPA627.jpg

It's all in the datasheet, so in this case you can replace OPA627 with OPA2107, nor vice-versa, as one is dual and the other one is single channel opamp. Unless you purchase or DIY the right adapter you simply can't swap them, otherwise applying voltage (+Vs) on PIN#7 of the OPA2107 (which is analogue output) will destroy the opamp.

Also, when swapping opamps you might want to check the recommended and max. voltage, the input type (FET, bipolar etc.), but also other parameters too.
 

sngreen

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https://www.ti.com/lit/ds/symlink/opa627.pdf vs. https://www.ti.com/lit/ds/symlink/opa2107.pdf.
It's all in the datasheet, so in this case you can replace OPA627 with OPA2107, nor vice-versa, as one is dual and the other one is single channel opamp. Unless you purchase or DIY the right adapter you simply can't swap them, otherwise applying voltage (+Vs) on PIN#7 of the OPA2107 (which is analogue output) will destroy the opamp.

Also, when swapping opamps you might want to check the recommended and max. voltage, the input type (FET, bipolar etc.), but also other parameters too.

And so I wonder, how did whatyougot swap those incompatible op-amps when not only it is technically impossible but if 'wired' to match one, by whatever schema, it could damage the other. I hope he comes out and clarifies it.
 

trl

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Like I DIY DIP8 adapters in the past to accomodate the new pinout, maybe @whatyougot did the same.
 

Colin James Wonfor

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Back again, after a longer hiatus than I had anticipated. Getting the drilling done was easy enough, but I lost a lot of motivation afterwards and just didn't feel like working on it. Fast forward to today and I'm only a few steps away from the testing stage.

View attachment 16107
Me and my uncle got the plates all drilled out. It's not quite perfect, but it's good enough for DIY. We accidentally went one size too large on the stepped bit for the headphone jack, but it didn't turn out to be a big deal.

View attachment 16108
At first, attacking the shielding to separate it was a real chore. I didn't understand quite how to do it and started with a flat-head screwdriver, as I has seen others do. Turns out the tip of an old multi-meter probe was a far better tool. You can actually unravel them if you take it in steps and have a precise tool.

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After soldering both the signal wire and the shield, I heat-shrunk them all closed and did the other side in red.

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I continued the process for the headphone jack.

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I asked in the official WHAMMY forums on diyAudio and was told that the capacitor that is shunted from the RCAs to ground is a non-critical value, so I used an old one, which had previously turned out to be too big for one of my other projects. I'm hoping I won't have any issues.

View attachment 16117
Creating the threads with these screws turned out to be a much bigger chore than I had anticipated. The screws themselves kept wanting to strip and the aluminum on this panel proved to be far more formidable that it first appeared, making turns difficult.

View attachment 16118
In order to fit everything and have it away from the transformer on the PCB, we had to stack the RCAs like this in order to have the IEC Inlet in an appropriate position.

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Back panel complete.

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Had to widen the screw holes on the front panel headphone jack and use a nut on the inside in order get it straight. Unfortunately, the initial measurements were slightly crooked, so it required tweaking.

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...and that's it for now. Next time I will probably finish. I'm going to include some thermal shots of the amp in action after it has warmed up (providing it works, of course), so that should be interesting.

Just a safety worry no bleed resistor on the cap between earth and chassis, maybe fit a 10M 300V type so if there is a problem the cap does not charge up, I have seen it and done, it bites.
Nice work.

I would also like to have seen PCB slot to help isolation between mains and human, OK the gap is fine but I have seen condensation on pcb cause trouble, so beware. I am a worry gut honest seen to many accidents.
 

Colin James Wonfor

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Back again with the finish.

Ran into some unexpected problems this time. The first of which was that I realized the outer screws holding the jacks in place were going to run directly into the outer perimeter of the case, preventing closure.

EDIT: (Forgot to mention that all photos in this post and the previous post were taken with my new camera, the Panasonic DC-G9 and the Panasonic Leica 45mm F2.8 Macro Lens, except the last image, which was taken with the Panasonic Leica 25mm F1.4 Lens, and the thermals which were taken with a Seek Thermal RevealPro.)

View attachment 16141
I ground them down with a Dremel. Unfortunately, this was my first time doing this, so it's not pretty (it's on the inside, so who cares). I wish you guys could have seen the sparks coming off the steel screw though! Too bad I didn't get a video of that.

View attachment 16142
New Problem! The board doesn't fit into the case. See the left (white) jack down there? It's in the way because we set it too low when drilling the holes. I have the beginning marks of the area I need to cut on the PCB. That's right, I have to cut into the PCB. By some miraculous fool's luck, there is nothing important there (It's just a part of the extensive grounding plane, it won't be missed) except maybe the standoff hole... but I'm not using them, so it's time to cut!

View attachment 16143
Measured and marked.

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Confirmed there is nothing there. No traces.

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I don't trust myself, so I put a bunch of tape to protect the nearby components in case of a slip.

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Little crooked. Doesn't matter.

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Now it fits!

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Just have to wire the inputs and outputs. Even with an appropriate tool, pulling the shielding braid out gets old... fast.

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Also remembered I still needed to fit an op-amp, so I went for my tried and true LME49720.

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Input wired.

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Output wired.

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Ready for testing! I didn't screw in the self-tapping screws yet, because they can only be put in so many times before they strip out their own holes... hence the crap-tastic tape job... onwards!

View attachment 16153
Test commencing! But there's a problem. I keep hearing crackling and popping. I'm devastated. However, I remember from the WHAMMY thread on diyAudio that they recommend testing many different op-amps if the one you choose doesn't work well. I have an OPA2134, so I put it in instead. It fixed the issue!

EDIT: Forgot to mention, the DC offset was measured and was negligible: less than 1 mV.

The thermal images are next. I took these at various intervals of the test. There wasn't that much variation between the temps over an hour. I've chosen some of the most interesting pics. They progress from earliest (around 10 minutes) to oldest (about an hour).

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Op-amp.

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The power supply MOSFETs got up to about this temperature after ~30 minutes and stayed there.

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This was the hottest that the other MOSFETs got.

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An overhead shot without the center reticle.

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The op-amp never got much higher than this. Since the OPA2134 max recommended temp is 85C (185F), I decided it was fine and didn't need a heatsink. There are some op-amps that operate at their upper limit (17V) when used in this design. Make sure you confirm what the op-amp can handle before using it. If it does approach its limit, you may have to use a heatsink on the op-amp or a different one altogether.

View attachment 16164
After testing, it was time to put it together and be done. I screwed on the panels, the volume knob, and put on some rubber feet. There's a slight gap where the backplate meets the top panel (it must have gotten warped during drilling or another process). It's not too bad though. Unfortunately, this amp doesn't really look new or shiny. There's a bunch of scratches all over it from mishaps during the build. It doesn't bother me, but maybe I'll get a blue Sharpie one day and try to touch things up a little.

Overall I'm really happy with it and am listening to it as I write this. It sounds fantastic, but that's just subjectivity. There's no hiss or anything I can hear, so it seems like a really good, clean amp. It also has a lot more range with the volume than my Millet Butte (and not so much gain), so I don't have to feather the knob on the low end to get even (but not deafening) sound. It gets more than loud enough when required. Also, there's only a slight blip when the unit powers on, unlike the Butte; which is loud enough that I started unplugging my headphones before powering it on.

If you've been thinking about building one, I say go for it! Feel free to shoot me any questions, or you can head over to the official forum at diyAudio, where there's a proverbial army of people who have already built this, ready to answer questions.

I'll leave you with a glamour shot...



View attachment 16165



Thanks for looking! Until the next time I find something to build...

I did not see ambient temperature measurement or a inside box one, can you please tell us what they are??
 
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