I need to revise my cmoy headphone amp because that DC offset still bugs me a lot.
I want to know what I did wrong or at least reduce the offset to an acceptable voltage 20mv to 25mv max.
After some light reading my conclusion is that the problem can be from: A bad ground plane, a bad chip, the power supply rails off-center (I’m pointing to this culprit because the amp has way less DC offset using a a true ground rail from two 9V batteries, too much gain, bad circuit soldering.
Now I shall rebuild the darn thing with those culprits in mind.
I’ll also remove the psu board after the dual AMB Sigma25, but the biggest change will be using the layout of the Grado RA-1 with its original 4.6X gain. I already talked with my supplier for the original chip of the Grado Amp with luck I’ll buy some soon.
If I can’t correct the DC offset I’ll go for the coupled output again.