How to Eliminate Hum? CDP + Pass Preamp + Amp Setup.

Have you checked your outlets with a receptacle tester? It is possible that circuit in your house is wired backwards or has a missing ground. Or, that one of the power cords you are using is bad.  

And don't leave the CDP out of the picture. It could be the problem and your current integrated isn't sensitive to that problem. Try a different music source with the Pass gear just to eliminate that possibility. 

OP sounds like the dealer has 9 more days to fix it, then.. Does the seller have any ideas?  Did it sound right where you picked it up from, and not correct at your place? 

1. Remove all routers and cable crap from that circuit. It should be on a dirty circuit (different). 

2. Everything on the same circuit. Get cheaters plugs and see if it goes away or with a PC swap, just for the sake of trying. No cost ay?

Regards

Mlsstl, I haven’t checked the receptacles. I have a Ground Fault Tester on order.

oldhvymec, I ordered it from a reputable Pass dealer sight unseen. I’ll get cheaters. The PC does wobble at the IEC plug. I’ll try swapping it out.

Thank you both!

If the cheaters work get an EBTech Hum X.

@88man 

Hum is a very specific sound. You can't hear it in the midrange or tweeter. I am assuming this is what you are hearing with the following comments.


Don't worry about hum if you can only hear it 6" from the speaker. That is pretty common. But the fact that the addition of the preamp causes the hum to be so much more audible is an important clue. Another important clue is the fact that the hum is affected by the volume control. If this were a ground loop problem or anything caused by the AC line you would be hearing a buzz, which is audible in the tweeter.


You did not mention if the CDP was connected or not when the hum was noticed with the preamp. If it was connected, disconnect it and see if the hum is still there. If yes, return the preamp for service- the hum should not increase with the volume; this suggests a filter capacitor problem in the power supply of the preamp.

If the hum goes away when the CDP is disconnected, have the CDP serviced out. Digital devices can make all sorts of sounds including hum when things go awry.