Help please... trouble shooting Nap 300 DR problem... one channel

Hoping someone can provide some feedback.

I had my gear powered down for about 2 weeks. Powered it up and I seem to have lost the right channel on my 300 DR. I’m getting sound out of my left channel but not the right.

I’ve eliminated the speaker cable as an issue, as when I switch the speaker leads the right speaker comes to life and the left one dies.

Here’s the really strange thing, and perhaps the clue to the problem. If I take the left channel lead from the DIN>XLR out on my 552 PS and plug from either the left channel or right channel out on the 552 PS into the left channel XLR in on the 300 DR, both of the out channels on the 552 PS feed the left channel audio. Which I believe eliminates the possibility of a problem with the 552 (this is a good thing I guess… looking for any good news at this point). If use the DIN/XLR lead that was previously connected to the right channel on the 300 DR, and attempt to run it from either of the 552 outs, I get no sound in either channel. So it would appear that this cable is completely non functioning. The cable that was previously installed into the left channel on the 300 DR will output sound from either of the 552 outputs into the left channel only on the 300 DR.

So it would appear that I have one cable that is shot… and that the right channel on my 300 DR is shot.

Is my logic here sound? Does anyone have any experience with similar problems… or suggestions on what I might be able to do to right the ship. Or am I heading to service-ville?

Any advice appreciated.


Remember the DIN > XLR are handed on the 300 and 500 so swapping left for right will result in no sound. Swapping these will not eliminate a fault with the preamp - is this on all sources ?

Thanks for the feedback. My point re the 552 outputs is that both are functioning… if I plug the left channel DIN in on the 300 DR into either of the 552 outputs… I get sound in the left channel. Which leads me to believe that both of the 552 outputs are functioning.

Yes it is on all sources (RP 10 and NDX 2).

Ok but the outputs on the 552 PS are not handed - both output L&R channels so it’s not an indicator of where the issue is. If it’s on both sources then it’s either a fault with the pre or power. Might be worth a full system power down and then power back up again to see if it’s a simple fault that needs a reset to clear.

I tried a power down but will try again :slight_smile:

Whilst the power is off, it’s worth checking all the connections from Pre to PS and from PS to Power amp. Also check the Burndy cables between the 300 and 300PS. Worth just pulling them out and reseating just to make sure all is well.

Power down did not resolve the issue.

I’m not really following how the issue could be related to the preamp if both of the DIN outputs on the 552 power supply are capable of sending audio?

Given that the DIN/XLR cable that was previously connected to the now malfunctioning channel isn’t working at all (ie. when plugged into either of the functioning DIN outs on the 552 PS or into either of the 300 DR XLR ins), and that the right channel of the amp isn’t outputting any audio regardless of which DIN output is connected, doesn’t this suggest that the issue is with the right channel of the amp?

I do have a chord TT that is not being used. I guess I could get some DIN > DIN leads and see if using the TT as a preamp resolves the issue.

But the cables you have to connect to the 300 are handed so whilst you can use either of the bottom two DIN sockets on the 552 PS, you must use the correct handed cable matched to the appropriate input on the 300 amp. They are coded green (ch1) and red (ch2). So what you have done is shown that the left channel is working in both sockets but you haven’t been able to prove you have a right channel working on either socket which to me means you can’t rule out either the pre being at fault or the power at this point.

Ok… I’ll power down again and then disconnect all burndys and interconnects and reconnect and then power back up and see what happens.

If that fails… does trying the Hugo TT as a preamp make sense to rule out a problem with the amp?

Shut down… disconnected and reconnected all cables… no success :frowning:

That’s a shame. If you can make up some RCA to XLR cables then that will help rule out where the issue is by using the TT but do you have a dealer nearby who could bring out a few bits of kit to try some substitution to work out the problem ?

Hi zipperheadbanjo,

While it is not inconceivable that you have a fault with the 300 or right XLR cable, my money is on a failed mute relay in the 552 pre.


1 Like


The Hugo has XLR outputs… so I assume I can use a standard XLR female > XLR male cable to connect the Hugo and the amp… no?

Interesting… when I booted up for the first time I thought the mute button on the 552 became dim a lot faster than it usually does when I restart the rig. No clue whether that is an indication of a fault with the mute relay or not.

The Hugo has balanced XLR outputs, the 300 is single ended (it just uses XLR sockets)

Neil’s suggestion is a good one and he should know so i think it may be worth involving your dealer to confirm it is the 552 and to get it fixed.

Thanks James… I’ll try to make this my last question. Well two questions actually.

With respect to testing the Hugo… therefore I would need two single RCA cables each with an XLR termination on the other end?

With respect to Neil’s comment… Is there anything I could have done to caused this problem? I’m pretty judicious with respect to following the shut down / turn on sequence… but I do know that when I shut down prior to going away for a couple of weeks, after powering everything down, instead of turning off my Audience power conditioner, I simply unplugged it from the wall. Could this have contributed?

In response to your last paragraph - not at all, just plain old component failure usually I’m afraid.


Yes - take a look at the back of the 300 to see how you would need to wire this. Each XLR input has either a CH1 / -ve or CH2 and -ve, See picture attached. Connect the inner pin of one RCA plug to the CH1 pin on the XLR plug, the outer to the -ve connection. Same with the other RCA plug albeit to CH2.

I doubt your power off sequence has done this. It sounds like it may be an issue that Naim are aware of hence Neil’s answer. I’m sure he will explain more. At least if you can get some test cables up, you can prove which unit is at fault.

Anyway hope you get it sorted and get your music back soon :slightly_smiling_face:

Sorry zipper - I missed your earlier post, the 552 will behave as normal with regard to the switch on mute period when it has a faulty mute relay, so it won’t give away any secrets!

We have used 2 or 3 different relay manufacturers throughout the life of the 552 - some have proved more reliable than others.


Thanks Neil… my serial number is 408xxx… does that provide any further clarity regarding the likelihood of it being mute relay?