I recently re-installed my 282 with nDAC front end and appear to have a grumbling mains. This is the first time I've installed the 282 in the current location, so do not have much data to go on. But, the setup is:
AV2: plugged in to av as unity gain
nDAC: plugged in to aux1
"Record" is set to mute with aux2 selected.
If I select the av input, all is quiet. Select any other input, including the nDAC aux1 input, and I have what is best described as an audible (normal listening levels), low grumbling, lumpiness of noise emanating from the speakers.
The closest analogy, if there is one, is that the noise is akin to the rollout groove on vinyl, but lower, more wavy, grumblier and not as repetitious. (I think I just described how different they are!) If left on one of these inputs for long enough, a louder "pop!" will occur at random intervals.
I tried changing ground on the nDAC from chassis to floating, but no change. I've removed the nDAC from the input and the noise persists across all other inputs. I'm working toward testing independent mains cables (currently a 5-way hydra) to see if the cabling can improve matters.
The other data point is that the volume knob on the 282 appears a little noisy when being moved.
Is this simply a case of lousy mains, or is there something else going on?
Thanks,
-Mark
Posted on: 21 November 2015 by Mark R
Richard,
Many thanks - I was just testing when you replied. With nothing connected to the 282, the sound is present on all inputs - this is true for av input as well, now that I have disabled unity gain. Does this point to mains, or still potential earthing issue?
Thanks,
-Mark
Posted on: 21 November 2015 by Darke Bear
It sounds like the 282 has a leaky coupling cap to the pot - you say the pot is noisy when moved and that is what a leaky coupling cap does, it injects noise just like you describe.
Also AV input I think bypasses the volume pot.
How old is the 282 - does it need a service?
DB.
Posted on: 21 November 2015 by Richard Dane
Mark, so have I got this right - you still have the low level rumbling noise even with nothing connected to the NAC282? But no problem when unity gain is on (i.e. pre-amp bypassed). If so, it seems to indicate a problem with the pre-amp, or possible the power supply powering it. Maybe a component gone noisy or about to fail? To be sure, are you able to power off the pre from a different PSU of from a power amp? That would at least rule out the PSU.
Posted on: 21 November 2015 by Mark R
Thank you, both.
Yes, with nothing connected to the 282 the low-level grumble is still present. The 282 is 190xxx vintage: 2002, yet to be serviced. The XPS is also 2002 vintage (189xxx) and have the XPS2 burndy.
I have a hi-cap I can use, to try and rule out the PSU. I also have a 180 - could that power a 282? I think I may have an older napsc somewhere - could that also be a cause?
-Mark
Posted on: 21 November 2015 by Richard Dane
NAPSC is just logic control and not audio, so i think we can rule that out. A NAC282 can be powered from a NAP180 - you just need the upgrade link plugs to be refitted.
XPS has nothing to do with the NAC282 so not relevant here.
Posted on: 21 November 2015 by Mark R
Good grief ... can't believe I did that; it's been a week, what can I say?!
Supercap2, 205xxx, 2004. None yet serviced, but have been in storage for a couple of years.
Posted on: 21 November 2015 by Darke Bear
The problem you are getting originates within the 282 head unit - changing the supply won't and can't fix it.
If it has not been serviced for nearly 14 years I think you are lucky that you managed to get that long before getting it serviced, but that is what you need to do to resolve the problem.
But it will sound wonderful once you get it back from service! 
DB.
