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 1 response by audioengr

Sounds like an internal ground-loop. I fix lots of these in my mods. They are common even in high-end gear.