"WHAMMY" Pass DIY headphone amp guide

So, 7.5V of DC offset is bad, right? Not mV, V. I have the power on, with my black probe in the GND out, and the red probe in the the RIGHT out on the board. Same outcome with the LEFT out. Pretty sure the board is stuff properly and the power supply testedproperly when I finished it. No smoke or crazy heat. I am hoping I am being dumb about measuring for offset.

I have attached some pictures, but can someone help me with a testing regimen to go through. I have the mechanical skills to stuff boards, but only a rudimentary understanding of what I am doing.

Thanks!

https://pzibyg.by.files.1drv.com/y4...4sU6OPjA?width=4032&height=1960&cropmode=none
https://pzieyg.by.files.1drv.com/y4...IaLQ7RiA?width=1960&height=4032&cropmode=none
 
Populate R3 and R5.

That will get the offset issue fixed. Without them the Opamp has no idea where it lives in relationship to ground.

Thank you! Now reading about 12mV on each channel. And I feel dumb about those resistors. I paid careful attention to not stuff them when building the power supply, then just went into stuffing mode after I finished.
 
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I am still working on casing, but after 6L6's help, everything is in good order and the amp sounds fantastic, even just out of my phone. I can't wait to get it cased up and start doing comparisons to other amps I have around. Thanks to all who made this amp a possibility, and many thanks to those helping us builders get working amps up and running!
 
Interesting. Can you define "better"?

well. yes i can. but it would mean nothing to you. unless you are running the same setup i do, and got the same taste in sound and listening to the same type of music that i do:) otherwise it's just taste. what i prefer would not be what you prefer :) its better to get a bunch of OP amps and just try them out and find the one YOU like best :)
 
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I finished it (finally)! It came out OK. I learned a lot about matching the board to the chassis. Also, still getting AM when I touch the aluminum knob, so I switched the knob to plastic. Problem solved.

9939473_l.jpg


Sounds pretty darned good with the Ether C 1.1, as well as the Utopia.

The way I built it, I can't really get to the board, so this one is done, and will not change. I'll probably build another and get the op amps suggested above to experiment. Thanks for the advice.
 
Tonight I tried the WHAMMY with a pair of sensitive IEMs (Sennheiser IE800S) and the stereo image is veering noticeably to the right.

With a tone generator, my decibel meter reads 1-2 dB louder on the right side, and my multimeter reads about .2 mV higher in the right channel.

Is this something peculiar to my build that I can try to diagnose and fix? Or is an IEM like this perhaps too sensitive for the WHAMMY?
 
Tonight I tried the WHAMMY with a pair of sensitive IEMs (Sennheiser IE800S) and the stereo image is veering noticeably to the right.

With a tone generator, my decibel meter reads 1-2 dB louder on the right side, and my multimeter reads about .2 mV higher in the right channel.

Is this something peculiar to my build that I can try to diagnose and fix? Or is an IEM like this perhaps too sensitive for the WHAMMY?

Scratch that! I swapped the RC4580 opamp for the LM833 (my AD823 is on the fritz), and now the channels are balanced (at least according to my 1/10 mV resolution dB meter). I'm not sure if that's due to a difference in opamp quality or something else.

By the way, it surprised me to see that the output voltage went from around 13mV with the RC4580 to around 23.5mV with the LM833. Is that strange? If I'm reading the spec sheets correctly, it looks like they'd be expected to have the same typical voltage amplification of 110dB?
 
Well, now I've really done it. I guess I should have left well enough alone and continued to enjoy my properly functioning amp. I swapped back to the LM833 to investigate the multimeter mystery for curiosity's sake, and now the ground has completely shifted under me, and I'm not really sure what I did to change things. This is what I'm seeing now:

- All three opamps (LM833, RC4580, and AD832) are working fine and behaving the same way (maybe last time I didn't push the AD832 far enough into the socket?).

- The channel imbalance has grown much larger to around +15dB on the right channel!

- The multimeter readings are very confusing. With the AD832 plugged in, I'm getting 0mv touched right channel and ground, and 4 to 8 mV touching left channel and ground. With the LM833 plugged in, I get a steady 23mV on the right channel, no matter how much I change the volume. The left channel is 10-30mV (increasing steadily as I turn up the volume). With both opamps, though, the sound is the same. I hear the test tone clearly, but +15dB on the right side.

- My rails are normal at around 17V and -16.86V.
 
Hello everyone. Two quick questions:

  1. What's the manufacturer and part number of the 1/4" TRS audio jack included in the kit?
  2. In addition to running a second set of RCA jacks in parallel with the headphone jack (with 100 ohm resistors on the hot leads to prevent oscillation), can I run a third set as a bypass set? Do I just tap directly off the inputs? Do I need anything else, like 100 ohm resistors? Lastly, can I tie all RCA grounds to the same ground bus with the final end going to the safety cap anchored on ground?

Thanks! Just gathering ideas.

Bump.