Hi everyone. Just a curious question. I have a 252 and whenever I mute or unmute it I get a fairly unhealthy sounding thump from my speakers. I’m fairly sure this isn’t normal, but I don’t think there’s any other issues with the amp, so wondering if anyone else has this or how much of a big deal it is? I only just noticed it recently since I picked up a pair of headphones and have started using the mute switch. Just for full info, it went back to Naim in 2019 and had a full service. Full setup is NDX2 and Rega P8/Rega Aria > 252/300DR with a Supercap DR and an XPS DR powering things. I did do a search and one result did pop up, but the video that guy uploaded has since been removed, so I have no idea if it was the same thing or not. Here is a video of my issue, since that will explain far better than me.
I have a 252/250. The mute on is inaudible at all preamp volume settings. The mute off is inaudible a 9 o’clock, barely audible at 12 o’clock and and audible tick at full volume on the 252. A tick, not a thump like yours.
All sounding a bit concerning then! The volume of the thump is completely independent of the volume, it can be turned right down and it’d be the same as if it was at 9, 10 or 12 o’clock.
It’s certainly not normal but may not be entirely attributed to the 252. I’m wondering if the phono stage may be affecting this. Have you tried with the turntable and phono stage disconnected? Maybe worth a few minutes just to eliminate?
I would try unplugging every source component. I once had this happen to mine and it was an earth leakage problem in an old Goldring turntable that was connected. I hope that when all sources are unplugged the noise stops.
Sadly it does the same with all sources removed. I took them out one at a time and no luck. I did discover it’s only thumping in the left channel though. I’d never actually paid attention to that before, as the left speaker is so close I just noticed that one, but yeah, the right channel is perfect.
That’s quite a loud thump on the speaker. Whilst I’d be tempted to try swapping the left and right speaker cables at the Power amp, I’d be concerned that there might be some damage caused to the other speaker in doing so.
I guess powering down and unplugging / re-plugging all of the Din / XLR, Burndy and interconnects might be worth a try. Nothing to lose in trying that.
It certainly isn’t right as it is and I’d be wary about damage to the speaker if you continue. I know that there have been some problems over the years with occasional failures of the mute relays in the preamps but I’m pretty sure these manifested as no output at all to one channel rather than the issue you have. @NeilS is more qualified than any of us on here to advise, if he is around.
Both my 82 and 552 produce a loud thump /click on mute. I now just select the next input along which is a totally silent way of doing it.
I suspect that rather like the mute relays in the Snaxo the pre amp output is simply being open circuited rather than switching it to ground via a low value resistor like I do in my home brewed amps.
That is probably one of the DC blocking tantalum caps in the 252 not doing its job properly any more & passing too high a level of DC. Especially as only one channel is exhibiting the issue.
A simple tant change should fix it (once the offender has been identified) & as said above - avoid using the mute until its sorted. It does look like quite a lot of DC!
Thanks Neil, I appreciate your input. Is this something that if I don’t use the mute button, nothing else is effected? If it is, then it’s pretty easy just to not use it and not worry about it for now. If it needs fixing then it needs fixing, but I’d rather not send it off again when it only had a full service a few years ago. Though I at least have a Muso QB now which could tide me over whilst it’s away!
