"WHAMMY" Pass DIY headphone amp guide

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#4,701
fubar3 said:
protect whammy opamp from overvoltage:

The Whammy build procedure gives 3 options for 7815 output voltage -- 15v, 17v, or 22v. This does not bother the MOSFETs but it could damage an opamp where the absolute maximum supply voltage is exceded. I believe that the opamp supply should be fixed at 15v so that variations in 7815 MOSFET settings or transformers do not cause faults.

I modified the Whammy with 7815,7915 regulators just for the opamp. I installed a gridded PCB by drilling holes in the non-functional fins of the toroidal transformer. I lifted the hot side of R35 and R36 so that the opamp is powered by it's own regulators.

Be aware that the MOSFET regulators suffer more stress when a higher voltage toroid is used. This occurs because of the increased voltage across the linear regulators. Also, the vertical heatsinks on the main board are not very effective without a cooling fan.
Click to expand...
It'd be better to place the additional reg PCB close to the OPAmp...

Extreme_Boky said:
I think the higher voltage after the regulators (+/-18V) is desirable for the MOSFETs and overall power output/drive capabilities. It is undesirable for the OPAmps... the JFET input ones (that would allow for DC sound path coupling. i.e. no capacitors) usually like to see no more than +/-12 ... maybe +/-15 V top.

If I were to make one of these kits, I'd add LT3054/LT3095 voltage regs to drop the rails down from +/-18V to +/-12V and then use my favourite OPAmp AD8066. That would be okay for the LT regs as well - they wouldn't need any heatsink due to a very low OPAmp current consumption.

Not to mention the very low noise environment established... for the OPAmp.
Click to expand...
 
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#4,704
Here's my (in progress) WHAMMY. I took the opportunity to design the enclosure in Fusion 360 to improve my skills. The top panel needs to be redone to fix an issue.
 

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#4,710
Hello vdupham,

nobody will be able to answer these two questions. Why? Because it depends on several factors.
The most important - listening taste.
More important in this design - the influence of the OPAmp.

But if you can get the Toshiba MosFets 2SK2013 / 2SJ313, then use them.
Between the ONSEMI / Fairchild FQP3N30 / FQP3P20 and the VISHAY IRF610PBF / IRF9610PBF
it is very difficult for me to hear a real audible difference. I think in a blind test I would fail.
I had the imagination, that the ONSEMI Fairchild have a slightly better?more? bass. But this is so marginal...

And the input caps (C1 and C5) are in my opinion much more important for the sound than the 22µF-caps (ELKOS). But this is my opinion.
The only way to find out. Solder caps in (that they are easy to desolder) - listen - decide what is best
for your ears.
Sorry that I can't offer a better answer! 🤔
Perhaps other WHAMMY-builders can chime in?
Cheers
Dirk 🙂
 
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#4,711
cubicincher said:
Hello vdupham,

...
And the input caps (C1 and C5) are in my opinion much more important for the sound than the 22µF-caps (ELKOS). But this is my opinion.
The only way to find out. Solder caps in (that they are easy to desolder) - listen - decide what is best
for your ears.
Sorry that I can't offer a better answer! 🤔
Perhaps other WHAMMY-builders can chime in?
Cheers
Dirk 🙂
Click to expand...
If you have a scope and a square wave input to the Whammy C1 you can see (at U1-1) that the square wave input is no longer flat. I believe that C1 at 1uf needs to be increased so the bass is not rolled off at 50hz.
 

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#4,712
Hi huge thanks to Pass Lab members and others to help me complete my build. I built my version Whammy, its mono version. I use IRF610/IRF9610 mosfet output and 2 single OPA445BM opamp. My headphone is Hifiman Sundara. Soundstage is outstanding, detail is so good with mature and neutral. And PSU part is LM317/LM337 with DC servo LF453, so zero noise or hum.
 

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#4,713
twofires said:
Just the stock one for now, but I've mounted the caps either side underhung so that I can play with some big opamps if required (although that input cable might need to be rerouted if I do).
Click to expand...
Just to update this @ArtNova , I grabbed 8 different op amps from Mouser (from the super cheap NE5532P to the relatively expensive AD746JNZ) and have just started playing with them for a laugh. I don't have test equipment for them, and know they likely make very little if any audible difference, but my logic is just to swap one in, and try it until I get bored of it.

Here's the full compliment I now have to play with in order of expense:

RC4580 (stock - seemed fine)
NE5532P (a tech friend said to stop here, but clearly I didn't listen)
NJM4556AD
LM833N/NOPB
LM4562NA/NOPB
LME49720NA/NOPB (currently socketed - seems good)
OPA2134PA
OPA2228PA
AD746JNZ (felt it was a bit sharp - probs not worth the expense for audio)

That lot all together is still cheaper than the cheapest discrete, especially if you leave the last one off.
 
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