When I use my C3 REF as DAC for my tube amp I hear Humming/Buzzing 60hz noise from both channels when the volume is at around 11 clock and its gets louder, also I tried different dac but there wasn't any hum/buz noise.
I assume its a groundloop issues but I also tried 2pins power plug for the C3 REFS PSU but result is same can anyone help me?
Am a little bit late for with a reply, I do hope you have resolved in the meantime your issue with humming. I suppose it's a ground loop, since I wasn't able to reproduce it, at any volume setting.
On another note, haven't listened to the C3 for a while. I periodically take some listening "sabbatical" from my different headphones, gears and preffered music as well.
After some break up period, it is nice to revisit the gear and the music. It is kinda buying it again. After clearing up the "listening history" and getting free from the bias reading so many reviews, coming back from "sabbatical" helps me to listen more objectively. Sometimes, with certain gears I am not anymore sure it was a great buy back then, sometimes I even regret buying it and something it makes me happy I did a right thing.
Last night, after returning to the C3 after some longer break, I was extensively browsing through several Tidal playlists and was just (again) overwhelmed with spaciousness and huge soundstage. I have deliberately chosen AKG K701 for my marathon listening session, because they have somewhat cooler and analytical sound. I was amazed how warm and non-fatiguing they sound. There was wonderful airiness to the sound and the bass was warm, but stil tight and well controlled. Compared my notes, back in time when I first reviewed the C3 and I think, I wouldn't write it differently now.
So, the C3 has confirmed a best buy and secured a firm place in my setup.