2. amps-preamps
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Need help from Pass X-600 + ARC Ref 2 MK1 user

I am matching Pass X-600 with ARC Ref 2 (MK1) and encountering a strange hum issue. I have tried couple combinations and it seems like the hum is coming from only X-600 + Ref 2. X-600 and Ref 2 do not seem to have any problem individually. Following are the combinations that I have tried and they show no hum at all.

1. X-600 + Pass Aleph P
2. X-600 + Wadia 861 (using build-in preamp)
3. Mark Levison 331 + Ref 2

I have also tried couple power conditioners and even power regenerator, but the hum still. I was told the hum might be from power & preamp impedance mismatched. However, it shows pretty healthy from the specifications. Any comments on this will be appreciated. Thanks in advance!
jshaw1004

Showing 6 responses by jshaw1004

jshaw1004 OP
53 posts
 
Newbee: Thanks for your comment. Yes, cheater plug is the very first thing that I tried. I think I can pretty much rule out the ground loop issue.
jshaw1004 OP
53 posts
 
Cytocycle: It humms out of the speakers and a little bit from preamp's transformers as well (no mechanical hum at all on X-600's). I have tried PS-Audio's HumBuster, but it doesn't help on the mechanical hum from Ref2. I am using balanced cables. X-600's take only XLR.

Newbee: Humm... I can't find input sensitivity from my X-600's spec. Do you imply that there is some kind of mismatch between X-600 and Ref2? The humm is somehow auditable from the listending position.

jshaw1004 OP
53 posts
 
I have tried Mark Levison 331 + Ref 2 at friend's house and no hum at all. The humm doesn't increase as I increase volume control. The humm occurs without connecting any sources from preamp, simply power amp + preamp. I have tried star connection and leave only one ground for fixing ground loop, but the humm still.

Newbee: What's in-line attenuators? Where can I get one? Will it affect/downgrade the sounding?

Thanks for all your comments.
jshaw1004 OP
53 posts
 
No, I don't have a dedicated line. I thought about the power issue at my home before, but why even the power re-generator (PS Audio Power Plant) still doesn't help?

Another symptom is that I still can hear the music playing while turning the preamp volume control down to the minimum. Therefore to reduce my preamp (gain) output can probably benefit to both... I will do the research on in-line attenuator. Thanks for your info.
jshaw1004 OP
53 posts
 
Internal ground loop? If that's the case, which unit needs to be fixed? Power amp or preamp? Thanks.
jshaw1004 OP
53 posts
 
After reducing the output gain from preamp, the humm goes away! Thanks for all your comments!
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