Are you running balance from your Bryston to the ARC? If you are, try a single ended cable to see if that helps. You mentioned running a couple CDP’s directly to the ARC so this probably isn’t the issue as I’m guessing they don’t have balanced outputs. If you are using balance on the Bryston try single ended.
Also if you’re running balance to your Pass, try single ended as well.
I had a ARC LS25 MKII at home for a short time on my Pass X250 and had no issues whatsoever and the older X250 has a higher gain output than the .5 series I believe. Have you had your tubes checked lately?
Also if you’re running balance to your Pass, try single ended as well.
I had a ARC LS25 MKII at home for a short time on my Pass X250 and had no issues whatsoever and the older X250 has a higher gain output than the .5 series I believe. Have you had your tubes checked lately?