I am just recently having some hum issues with my X250 since I am still runingthru a non-dedicated power line, and I am sharing power withthe christmas tree!!!, once the tree is off hum issues dissapear.
A few years ago, I had a Pass X150 and bought a REL sub. I could not get the REL to work properly and could not get a good explanation from either Pass or from Sumiko, the US disctributor of REL. I returned the REL. I still do not know what the problem is with this pairing. Never had any hum problems with the Pass however.
Simon- you wrote-
"Probably the least of my worries as the Pass has been plagued with problems from day one and my patience is at an end".
I own the X-250 and a X2.5 Preamp, and have dealt with the Pass folks. I found them to be extremely customer focused and pleasant people, including Nelson himself.
If you feel in any way that your Pass X-250 is less than it should be, I recommend calling Peter or Nelson @ Pass Labs. I think they're great guys and will go the extra mile to help you.
Thanks for that guys.
Seemingly because the Pass is not grounded at the speaker terminals (floating earth, I think is the term, something to do with the balanced design), it will upset things by the sub only being grounded to one terminal(or not as the case may be).
The REL manual mentions that in some cases the sub will hum if the power amp is switched off.
This was the case when I hooked the REL up to the PASS - I simply switched the sub off before putting the Pass in idle mode. It seemed to work just fine and caused no problems when the Pass was powered up.On taking advice I decided it was best to leave the sub out of the system, a shame as I am late to the fold but really think a sub opens out the midrange when used sparingly. I am not a bass freak but given the REL brings more to the table than the Pass, I wish I had known this in advance - think I'll stick with my Nu-Vista and the REL - I like an approximation of real music, not really interested in an initially 'hi-fi' sound which palls greatly on serious listening.
I used a rel Stentor with Pass Aleph 2 Monos. I connected the high level negative imput of the rel to one of the spare outputs from my cd player via Radio Shack RCA connector (Wadia 860 - no preamp). The 2 plus wires were connected to a plus on each monblock. Worked fine. Maybe that could work the 350s? Just grab a ground some where else in the system.