Transformer hum.

Posted by: dave marshall on 23 October 2018

Bit of a puzzle here at Chez Dave.

My HDX returned home last week, having been back to Naim for a service, part of which included a new internal power supply.

Since re-installing it, I now have a fairly annoying hum coming from the second of the two 555 PS power supplies connected to my ND 555, something which was not there when the ND 555 was installed by my dealer, using the new Burndies supplied.

Now, the only connection between the HDX and the ND 555, is via a Cisco ethernet switch, so it doesn't seem possible that re-introducing the HDX could induce a hum in a power supply to the streamer?

They do share a common Musicworks Lite power block, but prior to the HDX going back to Naim, there was no trace of hum whatsoever, and there is no hum coming from the HDX, even though it now sports a new power supply.

The streamer power supply itself is a 3/4 years old DR version, so for it to have suddenly developed a fault at the same time the HDX was re-introduced would surely be too much of a coincidence.

I'm currently somewhat baffled, so anyone with some knowledge of all things electrical got any ideas?

Posted on: 23 October 2018 by james n

Dave - Can you move the HDX onto another circuit, or at least off the musicworks block. I suspect this may now be upsetting your second 555PS. I take it the mechanical hum from the 555PS goes away if you power off the HDX ?

Posted on: 23 October 2018 by dave marshall

Hi James,

The hum does indeed vanish once the HDX is completely powered down, so I've removed it from the distribution block and plugged it into the second wall socket which is adjacent to the one powering the Musicworks block. (I don't have a dedicated circuit for the hi-fi).

Silence is golden, and I'm completely hum free once more.

This would suggest that it's the replacement  internal power supply in the HDX which is the culprit, though I still don't understand why it was causing this problem.

Anyway, I'll take the pragmatic stance, and not worry about it, since shuffling things round as you suggested has delivered the desired outcome.

Many thanks, James. 

Posted on: 23 October 2018 by Bryce Curdy

One of the more frustrating and random things about Naim.  9 times out of 10 not a ‘fault’ as such, but bloody annoying particularly when it’s a new and unexpected development like this.  I know the domestic electrical supply is at least if not more to blame but that won’t change for the benefit of a few high end audiophiles anytime soon.

Posted on: 23 October 2018 by kevin J Carden
dave marshall posted:

The hum does indeed vanish once the HDX is completely powered down, so I've removed it from the distribution block and plugged it into the second wall socket which is adjacent to the one powering the Musicworks block. (I don't have a dedicated circuit for the hi-fi).

Silence is golden, and I'm completely hum free once more.

This would suggest that it's the replacement  internal power supply in the HDX which is the culprit,

Hi Dave,

it does seem the repaired  HDX is the trigger, but if it’s still on the same ring but now no longer a problem then I’d be thinking that either the issue is somewhere in the Musicworks or the ‘new’ HDX for some reason no longer likes being on a common star earth with the other boxes? A curious one for sure. 

Posted on: 23 October 2018 by dave marshall
kevin J Carden posted:
dave marshall posted:

The hum does indeed vanish once the HDX is completely powered down, so I've removed it from the distribution block and plugged it into the second wall socket which is adjacent to the one powering the Musicworks block. (I don't have a dedicated circuit for the hi-fi).

Silence is golden, and I'm completely hum free once more.

This would suggest that it's the replacement  internal power supply in the HDX which is the culprit,

Hi Dave,

it does seem the repaired  HDX is the trigger, but if it’s still on the same ring but now no longer a problem then I’d be thinking that either the issue is somewhere in the Musicworks or the ‘new’ HDX for some reason no longer likes being on a common star earth with the other boxes? A curious one for sure. 

Yes it's a strange one, though the hum, (to a much lesser extent),  did return shortly after I had moved the HDX from the Musicworks block, so I've now taken it out of my music room completely, hooking it up to an AirPort Extreme base station in the lounge, which provides a separate network for my music, and is directly connected via ethernet cable to a Cisco switch in the music room.

Most odd, indeed.

Mind you, since the HDX internal power supply was changed out as part of the service, I'm guessing that it is, as you suggest, the trigger for the hum, but I don't really want to have to return it to Salisbury yet again for investigation, so can happily live with things set up as above, assuming I remain hum free.