Supernait 3 hum

Just got a Supernait 3 and really pleased with sound. However, an unacceptable level of mains hum.
Having looked on here, and other resources, there seems to be a possible variety of causes - faulty unit, grounding, 'dirty mains etc etc.
A couple of ‘knowns’.

  1. My old kit did not hum at all - same mains sockets etc.
  2. I connect my friends NDX - the hum disappears.

My question is quite specific, why does plugging in a NDX ‘cure’ the hum?

1 Like

Naim amps signal earthing is through the din connected CD player which is why when ndx connected it’s all good, I suspect you have another source connected that is not earthed. Does it hum with nothing at all connected to the inputs? It shouldn’t

4 Likes

Was it Naim or another make?

Is the hum through the speakers or is it a mechanical hum from the casework?

Try this

2 Likes

Thanks for the update, the ndx was connected to the SN3 via rca and no other audio or power connections to either unit. So, the ndx was plugged into the same mains extension lead as the amp, the connection to the amp was rca, the amp was only connected to the ndx (i.e. no other inputs). No hum.
Take away the ndx and connect my irdac to the same input as was the ndx and the hum appears.
I’ve just disconnected the sole inputs on the SN3 and the hum goes.

Linn, Kairn Pro and LK140. Both now not in service (i.e. not connected to anything, mains and audio).

Speakers, I’ve just disconnected the speakers and there is the faintest hum from the amp (i.e. I had to press my ear against the case) and not audible even a few inches away. Plug the speakers back in and the loud hum reappears.
Not sure if this is relevant, the hum get louder when the volume goes up.

Thanks James, I’ll give this ago and report back.

Brilliant!! Thank you so much James.

1 Like

It’s the dac then which is lovely likely only got earth and neutral, so do the short bit of wire workaround in the linked post and all will be good

Thanks for your pointers Hifi-dog, it’s worked a treat.

1 Like

A follow on question (for James?) if I may, in the other post with the workaround/solution James says “I’d recommended making up a more permanent solution using a metal outer DIN plug.” - how would I go about this?
Would I need something like this? https://cpc.farnell.com/prehkeytec/71430-050/5-pin-din-plug-locking-180deg/dp/CN00750?st=5%20din%20plugs
And if so, what’s needed to be done?

That plug is a 180 deg plug so would fit into one of the input sockets (such as AV in/out). It’s only the outer of the DIN socket you need to make contact with . I’ve think I’ve got some DIN plugs knocking around in the lab at work, so I’ll take a couple of pics tomorrow to show how you could make up a more elegant solution.

I wrapped the wire around the din nearest the earth post and secured it with black insulation tape when I had hum from chord Qutest. This was resolved when I added an earthed linear supply for the Qutest. No hum or wire needed

Thank you James, much appreciated.

Thanks for the tip, how are you finding the Qutest?

brilliant! dare i say im enjoying it more than my previous nd5xs2…?

I found I didn’t have any DIN plugs so apologies for the drawings. Usual Caveat - if unsure about doing this, seek advice from your dealer.

Taking a typical Preh DIN plug, internally you have the black plastic front assembly holding the pins, with a metal bracket that clips onto this front assembly. This bracket would usually provide an internal strain relief (and also terminate a screen if needed) for the connecting cable. When the DIN plug is assembled a small screw secures the metal bracket to the metal outer case.

Mains earth is connected to the casework of the Supernait 3 and as the DIN connectors are mounted to the chassis, you can use this to connect signal ground (0v or -ve) to mains earth. Here are a couple of ways to make this connection-

Make up a short cable with a round solder tag at one end and spade tag at the other. The round tag goes under the securing screw on the DIN plug, the spade tag to the Supernait 3 ground post.

Solder a wire between the -ve pin on the DIN plug and the metal bracket. No external wire needed to connect to the ground post.

1 Like

Thanks for the info, glad you’re enjoying the Qutest, it’s one of the DACs on my radar…

1 Like