2. amps-preamps
  3. 1108769076

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
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.
mybuddy
16 posts
 
i have an arc ls25 mk2 with bryston 7bst. these components i believe have very similar impedance specifications as ur arc and pass. both components are dead quiet and even with my ear to the speaker, no noise.

i don't think its an impedance mismatch. i recall reading something from the pass website that the x600 amps can be driven by anything and impedance mis-matches is rarely a problem.
audioengr
3,282 posts
 
Sounds like an internal ground-loop. I fix lots of these in my mods. They are common even in high-end gear.
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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