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

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.

Nope. Not implying anything. I'm sure your X600 is probably just fine and the match up may be fine as well, just that the noise could be normal. I thought you might just be new to tube pre-amps. Continuing on that assumption....

Tube pre-amps in general just are not as quiet as SS pre-amps. Do you hear the hum when the volume control is at its minimum level or do you only hear it after you rotate the contol well past 12 o'clock? Do you hear the noise with any source input selected or only with phono and with a phono pre connected?

Hearing the hum at the listening position is not good if your volume control is any where near a normal listening level or at its minimum. If you are hearing this hum with only certain sources, like phono and only then with the volume control rotated well past a normal listening volume you may have a poor source or, in the case of phono inadequate gain for your cartridge. With some some sensitive amp and efficient speaker combos amps I have inserted in-line attenuators to bring the "noise" floor down to inaudible levels. Am I helping you yet?

If it humms out the speakers it's a ground issue, I tried a hummbuster also and it didn't work for me so it's not a huge DC problem. The Pass's already have a DC filter built in.

Have you tried the preamp at someone else's house to see if the transformer humm problem or an interaction/power/ground problem. ARC has great support.

Try floating the ground on the CDP, and then preamp , and then break the ground on one of the amplifier monoblocks (not both).

I had an identical Humm problem on ARC LS2B into a pair of Rowland 7M monoblocks. Humm was from speakers and was insensitive to volume control. Humm went away when I applied a ground cheater on LS2B.

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.