Buzzing valve power amp

I have the following set up: NDX analogue out into 272. 272 pre amp into Bel Canto C7R integrated.
C7R into David Berning valve power amp. This all works perfectly but I really would like to dispose of the C7R integrated. However when I connect the 272 via pre amp out directly to the valve power amp I experience a moderately loud buzzing sound which appears after a few seconds and goes away if I switch off the 272. The noise gets considerably worse if I switch the grounding switch on the 272.
So to recap - no noise when 272 connected to integrated but buzzing as soon as 272 connected to valve power amp. Any help from this forum would be gratefully accepted.

Sounds like a grounding issue somewhere. What type of leads are used from the 272 to the power amp. DIN-RCA, DIN-XLR, RCA-RCA?

If anything ending in XLR, I might suggest just trying with a cheap RCA-RCA (if your amp supports it).

Thanks for reply. Using rca to rca - the only available connection on the power amp.

Not sure what to suggest. It is a signal grounding issue somewhere but not sure where. Generally, having the 272 left on Chassis is the way to go. The fact you said it get even louder when switching to Floating is a bit concerning.

I’d test that out. Set it to Floating and at the power amp end get a bit of wire to touch the outer conductor on the RCA inputs to the case (Creating a signal ground to the case). Does that cause it to stop. get louder, do nothing?

Hi J&V,

Are you based in the UK?

M

Hi M
Yes - based in Essex.

Ground loop problem - difficult to get rid off in this set up.
One would need an isolating transformer between 272 and the valve amp.

Thanks Adam. Is it the valve amp that creates the problem. There is no buzz when I connect 272 to my Bel Canto integrated?

Does anything change if when it is playing you touch the power amp casework and that of the 272?

I had grounding issues a year or so ago, although I didn’t realise it as the effect was subtle, and when I tried to solve it using isolation transformers I made it worse; but it did help me to understand what the issue was.

My understanding is that these issues arise when you have more than one route to earth. In my case this was being caused by having items that did not ground to the mains, I had a such few devices including LPSUs. I bought an earth terminal block and ran cables from a metal point on any such device back the the block, and then one from the block back to my pre-amp earthing pin. That solved the issue for me.

By the looks of it.

Many thanks for your assistance, Mr U. I am going to solve my problem by taking advantage of the Offered discount from Naim and part exing the 272 for a NDX2!! That should get rid of the loop!!

:grin: