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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 4 responses by newbee

newbee
4,795 posts
 
Dumb question time. Have you tried using a cheater plug on the amp?
newbee
4,795 posts
 
Well, here's another dumb observation....If you are listening to noise with your ear near the tweeter/midrange and if your amp has a highish imput sensitivity you might just be listening to the noise floor of your amp, or its tubes. When I crank up my SP10II I get both a light hum and tube rush using two different amps, one with a .5 and the other a 1.v input sensitivity. With a third amp and a 1.5v sensitivity I get very little noise or hum. A different tube pre-amp is dead quiet into the same amps. Both with my ear at the speaker.
newbee
4,795 posts
 
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?
newbee
4,795 posts
 
The in-line attenuator that I was referring to is made by Rothwell. It is, in essesence, a resisor that is placed within an adaptor that you plug into your amp and then plug your I/C into it. You can buy these on line. They reduce the pre-amp output by 10db and in my system its enuf to lower the pre-amp's line stage noise floor below audibility. Cost about $60 on line for a pair.

About your problem - I've not a clue. But since it wasn't a problem at your friends house, it must be something in your power supply. Do you have a dedicated line, etc?
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