282 Noise - Suggestions?

Hi, the collective. I’ve been running my 282/HCDR into my 250DR for some time. As well as stereo, I also use it in unity gain mode for AV throughput from my Arcam AVR20 for TV viewing, both 2-channel and multi channel. The mode change from an audio input to AV (everything supplied via the relevant 5-pin Din) and back again has always been silent, but now there is a sharp, loud and somewhat alarming ‘crackle’ through the speakers. It’s only momentary, and the performance seems unaffected, but I’m concerned. The only significant change has been a move from a Grahams Hydra (fed directly from the wall socket) to Powerlines from a PowerHAUS M6. Does anyone have anything to offer, or a similar experience??

Many thanks in advance

No harm in unplugging all the cables and reconnecting them as a first check.

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Do you still have all the same items you used to have powered by the Hydra, now powered via the M6 block ?

Going to unplug/re-plug tomorrow. No changes to equipment otherwise

Does it do this with the volume control all the way down?

Makes no difference where the volume is set. Also, to be clear, it is only a problem when switching between any standard input and AV (and back) - if I switch between any two normal audio inputs it’s fine. And, as I said, once the switch has been made it works perfectly. The sound is similar (identical?) to that which occurs if you connect a source without having first powered down. Not that anyone here has ever done that…

powerlines properly shoved in?

As hard as I can without them sticking out the front - but the noise predates their arrival, and was there when Powerline lites were in place (as two still are, on NAPSC and ND5XS2 - upgrading slowly)

ah having re read, does it only occur when you change to and from AV mode? if so it could be a dodgy relay.

One thing to note from your system profile is that you may not have a source providing the signal ground to mains earth connection that a Naim source usually provides in a Naim system (you are using the digital output from the ND5XS2 and this is coupled via a pulse transformer so not galvanically coupled).

I’d suggest a simple thing to try is to plug the DIN5 interconnect that comes with the ND5XS2, in between the ND5XS2 analogue output and a spare input on the 282. With the ND5XS2 switch set to default (chassis) you now have a known signal ground to mains earth connection. Worth a try.

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Exactly that

I’ll try that - thanks

As I understand Naim source selectors, the noisy digital circuits are only powered up when you use them, once a source is selected they go to sleep. When using AV bypass, the power amp is effectively on full volume so it kind of makes sense to me that you would hear some noise when switching to AV but not on any other source. I get a brief taste of this when I select any source on my 52. There is a little barely perceptible hiss as I press the buttons which almost instantly disappears.

Unfortunately this is not a gentle hiss - it’s a sharp static sound that you can hear across the room

Would the earth connection still be live with BNC selected as the ND5 output?

Yep. The signal ground connection is always there whether analogue or digital output is selected.

Awesome. Once my four dogs have finished chasing me around Exmoor I’ll give it a go!

Tried it - sadly no difference. I even tried a spare SNAIC but that was the same. Any further ideas anyone?

Barring a strip down and recheck of all the connections as already suggested (which is always good to do routinely) further up the thread, to rule out a possible problem with the 282 (which I think unlikely) is to temporarily put the Hydra back in and see if the problem goes.

One of the issues with using AV kit integrated in with the Naim Hi-Fi is bringing leakage current in from other items attached to the AV side of the system – TV’s, set top boxes etc and this may result in the noise you now get when you initially switch to the AV input. With the change from the Hydra to the M6 block, you’ve subtly changed the mains wiring configuration from star to bus bar and this may be enough to make a difference.

AKA unity gain. I think Paul has a point. The fact that it used to be quiet but now is loud suggests a fault in the AV or a connection issue (with the AV).