Noise problem that goes away at max volume

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#22
I just ignored the loudness pin.
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#23
You've selected a 100K attenuator which is a reasonable choice; assuming a relatively low impedance source (eg. your iPad), the max impedance presented to your amp will be at -6dB position and will be 50k//50k = 25K. I suspect if you correct the missing cable shields, you'll be able to use the attenuators as you originally intended.
 
#25
That's a good point, Mark! To get a handle on permissible capacitance with 25K source, if we assume that -3dB at 100KHz could be tolerated, load C would be about 64pF.

@anhhct, do you have a handle on input capacitance of your amp, cable length between pot and amp input, and any spec on capacitance/ft. of the cable?
 
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#26
A 10 or 20 kOhm one will be less noisy. 100 kOhm is a bit old fashioned, even decades ago 50 kOhm was more or less normal. Modern sources can drive even 1 kOhm or less but that would be a hard load for the odd exception that may be in your chain.

That having said, I think you have a grounding problem in your amplifier and I can not make anything out of the PE/GND scheme as I don't see any connection to PE in the drawing?! Reread your posts and it is hard to believe you don't have PE in your home. If not then you'll have to do with GND only. Usually a sturdy 100 Ohm resistor from the central GND point to casing works OK both ways. Floating metal chassis work out less favorable usually.
 
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