[mr_bill]

I’m puzzled:

I have my vintage Onkyo T9 tuner (which has a variable output) rca’s connected directly to my PS Audio S300 amp.

With the Onkyo tuner’s power OFF - when I twist the Onkyo volume control up and down, I can hear some scratchiness through the speakers. Remember - that is with the Onkyo powered off.

How could this be?

(I imagine the volume control needs to be cleaned but why would I hear this through the speaker with the Onkyo power off?!)

[JerryM]

I would ask Frank at avahifi.

[richidoo]

I get a transient snap from my turned off diy amp when I shut off nearby florescent light. It continues happening for a few days after I used the amp then it stops until I run it again. Probably need a drain resistor on the PS caps.
Ghost of Tesla playing tricks on us.   

[Wayner]

Generally, all inputs in a preamp are tied together (shield wise). I suggest turning the volume of your tuner down and keep it there. Increase the volume on the preamp to make up the difference.