OPA1656 Phono Preamp: Split from OPA1656 thread

[JRA]

Are you shorting out the 'unoccupied' input or at least using something akin to a cartridge. If the input is open circuit, I'd expect to see 'some' crosstalk.

Only a fully balanced input would show 'low' crosstalk when OC.

I tried a 1K across the ghost channel RCA input and the output ghost disappeared. Yes a balanced connection would usually cancel out a ghost IF it existed on both +and - wires.

 

[JRA]

Regarding @JRA 's crosstalk: does it get better when you terminate the unused right-channel input with some impedance well below 47 kohm? When you short it, for example?

I lied when I said that with 1K shunt on the ghost input channel the ghost output was gone. Yesterday I saw a true shorting plug in my bench mess and tried that. Ghost output got cleaner. With the scope's minimum 10mV vertical res, I could now see that I missed something with the 1K plug. 4.4mV across 1K = 4.4uA! That's 4400x the op asmp's Ib. See pics taken yesterday before the following steps done yesterday and today.

I've ordered new Rs and Cs for repositioning of C2 and C20. I found a Pany 2.2uF metallized-PP with 7.5mm lead spacing that should go in, albeit tall. > > I've solder-coated the two outside +/- rails and the two outside Gnd rails with no change.
I tried running the "orange" wire on the board's backside but got similar results as the original positioning. = no help.
As before: Blue = driven Left channel output (8V) and Yellow = ghost Right channel output. Input signal = 40mVpp = 14.1mVrms