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

HELP! How do I eliminate Hum? I just bought a demo, Pass XP-22 and X250.8. 60Hz hum is audible across the room at no volume. It’s only a 60Hz hum, not 120Hz/buzz. Here’s the setup into same AC wall plug.

Amp only (no Preamp): Very slight hum audible inches from speaker
Amp + Preamp: 0 Volume: Slight hum audible 6 ft away
Amp + Preamp: 01 Volume: Slight hum audible across room.
Amp + Preamp: 99 Volume: Moderate hum audible across room

I tried the following without any success:
- Connecting CDP
- Used different interconnects
- No cables touch nor cross.
- Separated the preamp from the power supply module.
- Used different AC outlets
- Used different AC Power strips for testing
- Each unit on different rack.

My integrated amp doesn’t have this problem.  The sonics are great, except for the annoying hum. I have 9 more days of trial period... How do I solve the hum issue without killing the sonics?


88man
mlsstl
1,379 posts
 
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. 
Ag insider logo xs@2x
oldhvymec
5,101 posts
 
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
88man OP
28 posts
 
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!
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