NAC62 - Normal/Mute/Monitor Switch [Snap, crackle and pop]

The short story is that when using my phono outs (with BNC to RCA adapters) for the first time in years, I had a lot of hum and signal drop out, unlike any other input.
I simultaneously tracked down a problem to the Normal/Mute/Monitor Switch . The physical lever is not functioning properly . Could these problems be related?
I now have a dysfunctional mute switch. Does anyone has advice for me to source a functional one or fix this one. I have tried an air blast and am looking for my contact cleaner - but it seems a physical problem.
As an addendum, NAP140 now seems to have ‘caught’ some hum when attached directly to my Topping L30 which it never previously had. Surely hum cannot be viral? I confess it was not socially distanced.
OK so that wasn’t short. But it could be longer.
Any advice on the above would be greatly received. I will try further diagnostics but the NAC62 is currently disassembled.

Hi Dave, when you say phono “outs”, what do you mean here, as there are no phono “outs” on the NAC62. If you could elaborate here, that would be great. Perhaps you mean the BNC input, which you’re using with BNC to RCA Phono adaptors? If the adaptors have gone bad then that may be cause. Can you try one of the DIN inputs instead?

Of course, if the mute and monitor switch is faulty then I guess that will need to be fixed. I would advise you to contact a Naim dealer to get it checked or else have a word with someone like Darran at Class A.

As for playing a non-Naim device directly into a naim amp like the NAP140, this is likely down to an interconnect or an earthing issue (or maybe both). I assume this was fine before with the L30 directly connected to the 140 and has just started to happen with no other changes?

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Depending on their history, most would suggest getting the 62 serviced. Class A is where a lot send their gear. Darran has serviced a few bits of my Olive range brilliantly. Nice guy yo deal with and you kit comes back ready for another 20 years service.

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I had a similar problem when using RCA/BNC adaptors. I seem to recall the RCA on the tone arm cable was not a tight fit on the adaptor. Problem went away when I used a different pair of adaptors.

In what way is the mon/mono/norm switch not functioning correctly?

@Richard.Dane I did mean phono in not out ‘doh!’. But I cannot see how to edit this. As it was my first post I did not get a sight of this error I need to remedy it.
I used an external phono-pre amp through the DINs with no problem - after I head earthed the turntable well.
The turntable phono plugs had a poor fit in the BNC to RCA adapters so I used my headphone amp as a pass through and used a higher quality phono cable into the adapters with a tighter fit. i had a cleaner signal then but still some issues with the integrity of the connection. However it was at this point that the influence of both the balance and the mute switch became apparent.
The switch does not ‘latch’ cleanly between the positions. Also it appeared to influence the amount of hum and the signal dropout of the phono input.
At this point I removed the NAC62 and detached the switch from the case to see if I could fix the problem. I cannot and the selection lever is loose and does not index into the 3 positions cleanly.
I went back to the NAP140 just as a power amp with the Topping L30 as a single input pre-amp as I was using before. I now have a background hum.
Thanks for the leads about the switch it looks like this will have to be replaced.
There maybe more than one thing going on here. So I need to try and eliminate the variables.
The BNC/RCA adapters were on the NAC62 when I got it and also remained there when Naim serviced it. I will investigate alternatives.

Hi @Fatcat
The mute switch does not ‘latch’ correctly in the 3 positions. It also causes hum, crackle and channel dropout when moving between the different positions. I detached it from the case body to investigate (ie. removed the nuts from front and back). The lever is clearly loose.
I have not tried operating the system with the case off and the switch loose from the case. I am wary of doing this.
Please can I ask where you got your new adaptors from? I was also wondering whether a cable with RCA Phono to BNC directly might be the way to go.
Many thanks

Thanks for the info re: Class A.
I did get the NAC62 serviced by NAIM in around 2005 (maybe slightly earlier or later) It has was a lightly used 2nd system and also has not been used for the last 5 years or so.
So I had hoped that a service was not necessary. I never used the Phono at all so I have no idea if the problem has always been there. I need to find my service paperwork to see if there is any mention of it. The phono boards in it were MC boards, I have just got MM boards but I cannot really test them properly because of the problems.

Apologies - I meant Phono Inputs. Doh!

OK. So 15 years since service and not much use since then? All should be good.
My 72s were 25 and 28 years old when serviced. There was no noticeable drop off in sound before they were serviced. Just their age pointed to a need.

Hello Dave

I bought a new low lost pair from ebay. I think I was unlucky in that, the original adaptor was slightly under size and the tone arm plug was slightly oversize. It was that bad, that slightly touching the cable would cause a channel to drop out.

@Richard.Dane . You are correct about the NAP140 hum - just interconnect issues.
I did major re-routing of cables and seem to have eliminated the hum. I am using ‘Gotham RCA to Din’ interconnects from UK-CBE off e-bay. The quality and build is good but perhaps the shielding is not up to the Naim interconnects. Given the price differential that is probably not a surprise. It was just a coincidence that this suddenly happened at the same time as other problems.
I will also chase up the potential RCA to BNC adapter problem - a new adapter seems the way to go. In the meantime I will use a separate phono pre-amp and see if I can further diagnose the mute switch issues. Hopefully getting there I appreciate the advice I am getting.

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The naim snaics I don’t think are shielded. However if you have done some dressing of cables and removeed the hum then good.

Err… hum. Oh yes they are. Quite definitely… :thinking:

Most cables of this type are made with their conductors twisted together, with an overall screen.

Many years ago, I had a NAC42 - which had its Switch fail - it became noisy/crackly. The switch was replaced, by my Naim dealer.

OK. Twisted pair with shielding is good then. Only reason I thought not, was because a certain hat wearing witch makes great claims about their alternatives being shielded. Anyway, sounds like a naim snaic is too. :+1:

Above is a picture of the ‘innards’ of a SNAIC-4 (it was quite difficult to get even this far…).

Looking down inside the DIN shroud, I can see a 5th conductor, chopped off (so I guess SNAIC-5’s and SNAIC-4’s are both made of the same 5-way cable) - and I can see a Screen.

What I cannot say is if the Screen is terminated - it is not at the end shown above.

So is it ‘screened’ or not…? It looks like the Screen istself isn’t used - but the cable is of 5 way twisted construction, so is effectively ‘self screening’ - any Common Mode efects will be cancelled out.

No SNAIC’s were harmed in the process of producing this message… :laughing:

That’s above and beyond for a Thursday evening! Any screening should only be earthed at one end. Typically that end is away from the source. Hence the direction of the cable fitment is important. But as you say they are twisted pairs as well.
But as its a snaic, it will have power and signal close together. Not normally ideal.

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Yes, but… the power is closely regulated DC.

I have resolved some of my issues. To try and troubleshoot I bought some nothing special: BNC Male to RCA FemaleBNC to RCA (JEEU) connectors off a popular website. Also a short ‘basics’ female to male RCA cable. I fixed the switch in the normal condition. and temporarily taped into position. If I get everything aligned and the ground tightly attached then all is good.
There are 2 interfaces that are weak points for my turntable and can affect the signal.

  1. The original phono plugs one of which is prone to hum and I need to replace .
    2)The RCA/BNC connection on the NAC where I cannot yet find an adapter with a tight fit.
    I don’t really feel inclined to have the turntable lead terminated with a BNC male plug - if indeed this will help so I will attach new phono plugs - but that still leaves me with 2)

  2. Research and online advice, has indicated that these switches:
    May well be suitable replacement parts.
    I have emailed Naim to try and confirm this is correct. But I may well get one of these and see if I can do the repair
    Anyway everything is working at the moment and sounds good even if the phono connection is not as secure as I would like.

@NeilS - might be quicker to go direct :slight_smile: