Advice please ... has anybody had this happen

Hi all I am gutted something strange has happened to my system. As you all know I changed my switch to the Aqvox SE and gradually the system got better and better. The bass in particular was superb - quick tight fast - great texture to drums etc. - the best I have experienced in any home system. Last night put on a familiar track - and all that had gone - like a switch had been thrown. Now the bass is ill defined not much impact - and has more of a one note - feel. This is particularly noticeable on bass guitar notes… I am sat there thinking WTF… I checked the speaker spikes… aghh yeah… her indoors had moved them a little … and there was some movement apparent…so I adjusted … eliminated any movement. Effect - zilch in-fact it was worse… !!! The only thing that was apparent that was odd … the NAP500 transformer was humming and grumbling a bit … so I am wondering if there was/is a mains issue that effected the bass tunefulness. Could it be an earthing issue… I have left things as is at the moment - and when I get home from work -I will test it again.

Has this ever happened in your system? and if so what was your resolution. How would you go about tracking this down. I am going to test the same track with headphones - to see if it is the source giving the issue… aside from that I am at a loss…:pensive:

One thing I have been considering for a long while … my NAP500 is 17 years old fully serviced and dr’d
however, the transformer has always been very very noisy and grumbly … at times audible above music!!! Having spoken to Steve Sells … it was confirmed that there have been some subtle changes to the transformer metallurgy over the years - resulting in much less boisterous transformers. So I am considering changing the transformer…but that desire was from a noise perspective…

Assuming that you aren’t suffering from Statement-deprivation syndrome following your day in Salisbury, it does sound to me like an issue with your NAP500. You could try leaving that off for a few hours (but leave everything else on) and see if that has any effect. I recently had an issue with a capacitor going down in a tuner (not Naim) and after being turned off overnight, it was much worse in the morning. So I knew that there was a problem to solve…


My 500DR is really quiet, just the occasional mains hum, but not enough to be even a minor problem. Back to Salisbury perhaps?

Do you already have dedicated mains?

Even on a relatively noisy transformer, when it hums loudly it usually indicates that there’s something nasty on the mains. It’s getting colder so I wonder of neighbours are switching on things like electric blankets (awful for provoking mains hum) or cheap electric heaters. As David suggests above. Try powering everything down, leaving for a bit, and then powering up again. Sometimes I have found that a system needs a sort of “reset” if things sound off all of a sudden.

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The improvement you heard may have altered the balance of the system. In my experience there can be a time lag as the system resettles. It sounds like a mains problem because of the hum. Mine was very loud when I first had it but the local supply was affected by the engineering work for a new incinerator. Look at the MusicWorks thread. My 500 is mostly quiet now. curiously the 555DR hummed before the circa 2000 552/500 arrived. It stopped immediately! There are explanations.


Humming transformers, especially intermittently variable, is commonly caused by DC on the mains, requiring a suitably rated DC blocker to stop it if the source can’t be found and eliminated. Dedicated supply to the system may help, but it depends on the source of the problem. To eliminate things in your home being the problem, try turning off everything else, and if that clears it bring them back on one at a time. If still present when all off then it may be something external contaminating the mains.

Whether that is of any significance to the diminished sound quality I don’t know, but it is an odd coincidence that the change has coincided with an audible change to the transformer noise.

Thanks everyone… I will do some more testing…I have dome theories… I need to try and eliminate those variables… so I can be confident in some form of diagnosis … doh

That’s what I thought…I wondered if some strange transformer harmonic was effecting low frequency signals…

The other thing different was my nuc running roon was quite hot…inc psu. I had … been doing some gaming…I wondered if the heat had effected the sound some how…

Your last post reminded me of an issue I had a while back with Roon. Response was slow and something didn’t sound right through both my lounge and headphone systems. The case of my nucleus which normally runs very cool, was much warmer than usual. A restart of the nucleus brought everything back to normal. I’m assuming something was not happy and putting some heavy load on the nucleus and a restart fixed it. No issues since and worth a try if you’ve not already done a restart.

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Right I am home again now…tried system … it is fine yipee!!! :smiley: WTF… whats going on :woozy_face:… my suspicion now is on the NUC/Linar PSU. Last night … it got pretty hot as I had a long session on World of Tanks…which stresses the i7 + GPU to the max … I immediately stopped gaming and started to listen to music… I suspect the heat somehow had an effect…perhaps thermal throttling???

I think you are right … somehow heat has an effect…now where’s nitrogen cooling kit gone…from my overclocking days…

I have noticed that NUC/Roon performance is variable - sonically … when cold superb … but as it heats up the performance fades somewhat… I am checking it out further…have others found this…??

It it on your HiFi dedicated radial?


Richie - My comment was really based on assuming (in my case) that something had gone awry with the Roon Core hence the sluggishness and the rather warmer case than usual - the laptop with a screaming fan scenario if you like. A reset fixed it and it’s never happened again.

I assume the hardware you are running the Roon Core on is up to spec and is as per Roon recommendations ?

There is definitely something to do with heat … I am keeping a watchful eye … I am wondering if thermal throttling is responsible… I repeated this morning…all was well for about an hour…and then it went off again… hmmm

OK … I am still concerned about this - I am going to have undertake some painstaking tests… in order to try and narrow down where the problem is.
So I was thinking - of doing the following…
Get a reference track.
Test 1 Copy ref track to USB stick …if problem disappears then there is possibly an issue somewhere on the ethernet side.
Test 2 Change preamp inputs … to see if there is an issue with 552
Test 3 Make sure Bluetooth is off altogether on pc (I have a sneaking suspicion that maybe this came on midway during my listening sessions)
Test 4 Disconnect one NAP500 channel … and see if I can Identify if it is one channel behaving badly.

Just to reiterate the problem is ill defined non tuneful bass … that seems to happen after about 30 mins of listening… all is well to start of with - fantastic…then you gradually notice bass is not sounding right …everything else seems ok… On one occasion when this happened … I noticed that NAP500 transformer was humming quite loudly - but I think when it happened again later… it was quiet…

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Naim has a fantastic SQ, a world class one, and a post-sales medal service, but, things up and thongs down, I begin to harbor the perception that, fundamentally, amplifiers tend to be a little unstable, or a little bit sensitive, or may be a bit picky…


Variable sound may suggest an issue with the receiver not the source too…