Hum sorted, but I don't understand what I've done

Hi-Fi Corner
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Disconnecting the DIN cable between the 282 and ND5XS2 (with the switch at default) removed another earth path in your system but didn’t find where this connection was being made. I would do the following…

Disconnect the REL sub and disconnect the AV amp connection to the 282. At this point the only other item (apart from the Hicap and NAPSC) connected to the 282 will be the Qutest. Connect the DIN cable between the 282 and ND5XS2. Set the ground switch to default. We’re not using the analogue output from the ND5XS2, we’re just using this connection to the ND5XS2 to provide the only signal ground to mains earth connection in the system.

Any hum ?

If no hum reconnect the REL sub (which model is this ?)

Any hum ?

If no hum reconnect the AV amp to the 282

Any hum ?

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Hi, thanks for the suggestion. I’ve moved some Christmas decorations around so that I can get to the system and followed it. As soon as I add the REL then the hum starts, and interestingly it’s actually louder without the AV amp connected than without.

When doing this I recalled that there is actually another factor I’d been overlooking, a LFE input to the REL (model is Quake) from the AV amp. When I disconnect either of these inputs, ie the LFE or the hi-level from the 282, then the hum stops. And it stops for both the original issue and also when using the AV channel on the 282. Feels liks a smoking gun to me :slight_smile:. Does that make sense ?

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Just to be clear, you’ve reconnected the DIN cable between ND5XS2 and the 282 and ground switch set at default ?

With the AV amp disconnected from the 282 and the LFE connection from the AV amp to Quake disconnected too, you’ve only got the Quake connected to the Naim system via the High level connections – I take it this is the usual 3 wire cable, L&R positive and a single ground. Any hum ?

If no and with no other changes to connections, connect the AV amp back to the 282 (don’t connect the LFE cable) Do you get hum – if so is it all the time or just when you select the AV input ?

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Yes

Yes, the usual 3 wire cable (connected as suggested by dealer to the speaker terminals on the SN3 not to the speakers).
No hum.

Interesting, I hadn’t tried that combination - hum, but only on the AV input.
I can remove it by setting the ground to float or of course by removing the DIN between 282 and ND5XS2.
Adding the LFE connection brings back the hum, again on the AV channel only, and that’s there no matter what I do with the ground or the DIN.

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Ok that’s useful info. These sort of issues tend to come when integrating AV kit with Naim kit and you’ve got an additional complication with the sub.

I’d keep the DIN connection between 282 and ND5XS2 to keep the usual Naim signal ground / mains grounding scheme in place.

With the LFE cable still disconnected. I’d try an isolating transformer between the AV receiver and the 282. This should stop the hum on the AV input. If it does then you’ll probably find it comes back when connecting the LFE cable again. If so then isolate this one as well with another isolating transformer.

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Thanks, starting to make more sense now (I hope). A quick search for ‘ground loop isolator’ brings up many products with pairs of RCA connectors. Not expensive. I’ll get one of those and see how it goes.

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Yep, that works, and for the LFE if I use it there instead. The latter also mutes a click I hear when switching input on the 282 to the AV. Will get a second one and should hopefully be done. Thanks

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Are you using the Qutest Dac because you find it sounds better than the ND5 XS2 Dac, or do you have to use it that way just to get it connected?
Just curious.
Thanks.

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Both connections work but I’m using the Qutest because it sounds better to me. It’s a subtle change and hard for me to describe, and certainly nowhere near the big difference it made with an ND5XS, but still worth it.

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We all have such different experiences with our gear. Often with the same components in a different situation. I find it very interesting to hear what works best with members different systems and different room setups.
It also helps, as I’m always looking for the best and least expensive way forward when I try to improve things.
Thanks again.

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Cheers, hope it helps. One day I’d really like to hear the MScaler on the Qutest :slight_smile:

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A lot of members that have the Dave also have the M-scaler and run out of superlatives when trying to describe the SQ.

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The second isolator arrived very quickly. I’d say it’s 75% effective - no noise on the Qutest input but a very quiet hum on the AV input. Not enough to bother me. Maybe the cheap isolators I’ve bought are only so effective?

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