Grounding problem of my OTL headphone amplifier

[ronardi]

I've just finished an OTL headphone amplifier, the sound is good, but it "hum"! the hum changes with VR volume. I've tried serveral ways trying to get rid of it, as the following:

1. connect the ground of RCA with a serial 1 ohm resistor to power ground in PCB.
2. connect the earth of power inlet socket to the chassis
3. connect the case of VR to the case of the amp.

is there anything wrong? plz help!

 

[eVITAERC]

Try moving the source & amp around a bit? If your source is too close to a computer or other RFI sources then no grounding scheme can really help you.