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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

Showing 4 responses by 88man

88man OP
29 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!
88man OP
29 posts
 
The CDP has makes no contribution to to hum. It’s only between the Preamp and Amp. The hum is audible from across the room. Nothing is connected in the room. I even turned off the lights, hum still present.

My $200 receiver (2-conductor PC) is dead silent at max volume on the same outlet. The house has never had noise/hum issues on any equipment. I’m going to order Hum X and Emotiva CMX-2. I’m discouraged and worried since I only have 8 days to sort this out.

88man OP
29 posts
 
I’m going to relocate the Pass XP-22 to another room. I’m using unbalanced RCA IC. I’m going to call Mark @ Reno.
I used the Pass X250.8 with my D. Sachs 6SN7 Tube Preamp - Dead quiet!
I ordered an Emotiva CMX-2 (Humdinger was out of stock). I’ll try the Cheaters too tonight.
88man OP
29 posts
 
With the XLR interconnects, the Preamp & Amp are dead silent! I wonder why the RCA connection produces hum?
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