Naim pop and hum at turn on/off

[Aussie Geoff]

I think this has been answered before but i cant find info on this when i searched the forum. I have a Nap12s Nap160 combo which i both recently recapped etc. I had not listened to my hifi for years before bringing it back to life ( "it started with a broken switch ", post). I seem to remember that whenever i turned on/off the power amp there would be a pop and a few seconds of hum, the level of which is not effected by the volume level.
After the recap I didn't get this pop hum at turn/off which i thought was a product of new caps etc but it is now doing it, i can't think whether it coincided with some event but i just started noticing it. Is it a problem?It has the same level regardless of volume control level. After turn on and the few seconds of hum everything functions fine - but there is a 50? hertz hum that can be heard when there is no input selected and i am within about 300mm of the bass driver(Kef3) - the volume of this hum doesn't increase if i turn up the volume , actually it decreases slighty as it approaches full volume on the control. Obviouly this hum can't be heard when music is playing but will it effect the quality of the bass response to some degree?
Thanks for any info.

 

[Eyebroughty]

This is may answer your questions about the pop at start and thump at switch off.

I have had a few amps that had a hum, just accepted that was pickup from some of the cables or RFI getting into the system

Anyway, read the Naim Manual, page 4 mentions the pops and thumps.

https://www.naimaudio.com/sites/def...wer Amplifiers Reference English Issue 2B.pdf

Cheers

John

 

[Gervais Cote]

I have a full recapped kit of 32.5/Hicap/160 BD and also have a pop when turning on.
My 32.5 is also fitted with Neil Jadman’s cards.
To avoid loud pop, I turn on the Hicap first, wait for a few minutes and then turn on the 160 and the pop sound is much less loud doing so.
As for the hum though, my kit is dead quiet, just like a brand new Supernait so no complaints about this !

 

[booja30]

My first Naim item was a Nait 2 that made a pop followed by silence, then the relay clicked and music started. When I switched to a 72/140 I was concerned at first because it made a pop followed by a loud buzz until the relay clicked. I started a thread to ask about it and also did some detective work looking at the relay board. IIRC the 72 when first switched on is 'floating' while the relay is open. Someone said it could be quieted by using high value resistors to pull down the input until the relay closed, but I just got used to it. In my case as well the buzz was independent of the volume setting.

I don't recall having any buzz after the relay clicked though. But I usually had something connected on the current input (even if not switched on/playing).

What if you have it switched to an input with something connected (e.g. CD) but turned off? Does it still make the noise? If not I'd guess that having it switched to an unused input is similar to having the relay open during startup.

 

[Craig B]

Agreed, you can't really judge playback hum levels using an unconnected input. The true litmus test would be to use a DIN shorting plug (or 2 x bent paper clips as jumpers, one across ch1 +ve to -ve and the other across ch2 +ve to -ve) with the volume set to a normal listening level on that input (just don't go touching the bare jumpers with the volume up!).

As to the louder hum until the relay kicks in, I've heard this on many an old NAP powered NAC setup; nothing to worry about.

 

[Aussie Geoff]

Thanks for the info. Glad the startup pop/hum is no problem, as i mentioned i did seem to remember this quirk when i was using the system years ago. The low level hum i have after the relay has kicked is something else. I did have a cd player connected when i noticed the hum at close proximity to the speakers, i changed input to other sources , also plugged the amp straight into wall socket instead of the power board shared by all the sources just to see if this made a difference but no,
there is a constant low level possibly 50 hertz hum. If i had to put my ear on the speaker to hear it i probably wouldn't worry about it but from about 300mm away it is discernible. I have just moved my system to another part of the room to take use of the longer dimension for the speakers ,maybe the new position of wires is the problem although the level remains constant where ever the vol control is set (slight reduction at maximum).I think i will have to move things around to see if it makes a difference. Just realised there now a router sitting on the floor right next to the speaker cables, maybe ? I suppose my main concern was that when i recapped etc the nac and nap that i did something wrong and created this hum. Currently i have three sources connected via a passive three in one out rca switching box so i will experiment with different sources both switch on and off and see what results, at work at the moment so i will try peoples suggestions later.

 

[Craig B]

The router will be DC powered and likely transmitting at 2.4 and/or 5Ghz. Unless your speaker cables are draped over the routers wall wart, there is unlikely to be any contribution.

Personally, I wouldn't be bothered by a bit of mains hum that I'd need to be within 30cm of my speakers to hear. At normal distances and listening levels this will be inaudible.