Some opamps will have some DC offset. I noticed it jumping from ~0.3mv to ~40mv on a couple opamps, though I don't remember exactly which ones. While quite high, it isn't high enough to damage headphones or anything. I would worry about the opamp not performing if it had an offset that high though.
I tested the offset cold with the top off, so not sure about it 'settling'. I would think that the offset would drop a bit when you put a load on it, though.
I tested the offset cold with the top off, so not sure about it 'settling'. I would think that the offset would drop a bit when you put a load on it, though.
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Ok.....I have the Whammy kit but not built it yet…….I still wait for the DiyAudio Store chassis.....that was promised some time back
I am in "M2X mode" …...and have just installed the pots for adjusting offset
to MEPER #1403
Hello MEPER,
don't worry! The circuit of the WHAMMY and the circuit of the M2X -amp
have a very similar bias adjustment via an optocoupler (4N35) in the outputstage.
WHAMMY does it fully automatic (most often), the M2X has the trimpot
for adjustment together with the optical bias adjustment (4N35).
It seems to me as there is the same 'father' for both 'kids'.
Greets
Dirk
Hello MEPER,
don't worry! The circuit of the WHAMMY and the circuit of the M2X -amp
have a very similar bias adjustment via an optocoupler (4N35) in the outputstage.
WHAMMY does it fully automatic (most often), the M2X has the trimpot
for adjustment together with the optical bias adjustment (4N35).
It seems to me as there is the same 'father' for both 'kids'.
Greets
Dirk
I had an old XLR to mic cable(which I never use) that I cut. Seems to be what most people are using(or similar).
I can't find a match to that PN.
Looks like W2791 or W2549 or W2944 would be good choices (bulk/markertek), the first two are mic cable and the third console cable.
BK
Basically any of the Mic cable (2-conductor plus shield) will work perfectly for the whammy -
W2552 Mogami W2552 Microphone Cable (Black)
W2549 Mogami W2549 Long Run Mic Cable (Blue)
W2697. Mogami W2697 Miniature Balanced Mic Cable (By the Foot)
If you order from there, spend 5 bucks and do yourself a favor and get 20ft of 2381 as well, it's a small flexible coax that makes great wiring to/from RCA jacks and such. My absolute favorite for wiring RCAs to PCBs. Mogami W2381 Black Coaxial Cable, 50 Ohm (By the Foot)
W2552 Mogami W2552 Microphone Cable (Black)
W2549 Mogami W2549 Long Run Mic Cable (Blue)
W2697. Mogami W2697 Miniature Balanced Mic Cable (By the Foot)
If you order from there, spend 5 bucks and do yourself a favor and get 20ft of 2381 as well, it's a small flexible coax that makes great wiring to/from RCA jacks and such. My absolute favorite for wiring RCAs to PCBs. Mogami W2381 Black Coaxial Cable, 50 Ohm (By the Foot)
You don't want a super fast opamp in whammy, (or honestly, in most audio devices) there's absolutely no need and it has the possibility of making it unstable and/or oscillating. If you have a slew rate thats 10 times faster than the absolute fastest music signal theoretically possible, that will be great, and still fairly slow when compared to video signals ad faster things. I.E., super fast isn't important, and can be detrimental.
Broadly speaking, a type that the manufacturer labels suitable for audio will work beautifully.
I really like the LM833 in this circuit as well.
So, for science, I tried my hardest to push the whammy into oscillation, but I failed xD
I grabbed a couple random video op-amps, and they didn't sound the best, but they also wouldn't push the opamp into oscillation.
I then said 'screw it', and grabbed the op amp with the highest slew rate I have on hand, the AD812ANZ, which has a 1600 V/ms Slew. For comparison, the LM833 has a 7 v/ms slow, and the LM4562 has a 20 v/ms slew.
Still no oscillation... and it actually sounds amazing. I gave up. That was not the result I was looking for xD
The weird part is I have sent preamps into oscillation before because of what you were talking about, but I would be damned if I could recreate it on the Whammy xD
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That takes away all the ambiguity - thx.
BK
MY WHAMMY
Hi
This is my WHAMMY in a different PCB and two single OPAs with offset adjustment.
All the components are from my shelve, that's why the resistors and the capacitors are different brands.
The PSU is seperated from the main amplifier, in it's own enclosure. It is dual with LM317,337 and 50VA (2x18v) transformer.
The R16, 22, 29 and R32 are replaced with 5.6 Ohms so as the bias is about 0.11 A.
The quality (using my old SENNHEISER HD540 Reference gold) is great with detailed sound and great focus of the stage. From all the ICs I think that OP627 is the best sounding.
It is the quietest phone amplifier I 've ever heard.
So I'd like to thank Mr Wayne for sharing his design with us.
Kostas A. Vazakas
Aigio
Greece
Hi
This is my WHAMMY in a different PCB and two single OPAs with offset adjustment.
All the components are from my shelve, that's why the resistors and the capacitors are different brands.
The PSU is seperated from the main amplifier, in it's own enclosure. It is dual with LM317,337 and 50VA (2x18v) transformer.
The R16, 22, 29 and R32 are replaced with 5.6 Ohms so as the bias is about 0.11 A.
The quality (using my old SENNHEISER HD540 Reference gold) is great with detailed sound and great focus of the stage. From all the ICs I think that OP627 is the best sounding.
It is the quietest phone amplifier I 've ever heard.
So I'd like to thank Mr Wayne for sharing his design with us.
Kostas A. Vazakas
Aigio
Greece
