Serious Interference Problem......Please Help !

I have to ask the obvious question. Has the 92/Flatcap/(and I assume NAP90) ever been recapped and serviced? The problem you are describing sounds less like an earthing issue (which I won't rule out) and more like worn capacitors.

Even though it stops when disconnecting the Flatcap from the power amp, I would not discount the chance that it is the power amp anyway. My money is on the Flatcap but if it is all of a similar age, getting the whole lot serviced and recapped together may be worthwhile.

Hi Feeling Zen,

I must hold up my hands and confess to no servicing.  However, I'd never heard of such an occurrence like this due to failing capacitors etc, and the SQ when the issue isn't there remains absolutely tip top.  Also the intermittent nature is a puzzle......

It would be good to test the NAP 100% through bypassing the NAC and going direct from DAC>NAP, but I haven't got a cable to hand which would facilitate that.  I guess I can take out the FC though, and eliminate that at least.....

A service where I live is probably an impossibility, unfortunately.   :-(

Okay then next simple question. Does it come and go at regular intervals or the same time each day? Does this coincide with anything like the motor in your fridge, the boiler pump or something?

That would then indeed be an issue with earthing, dirty mains, or RFI (though the problem seems a little extreme for the latter). At this stage I think there are 3 possible boxes and 4 possible causes. Shame there is not the lead you mentioned so you can test the boxes independently.

You can always get stuff serviced. Come time for my recap, I will need to send 6 naim boxes 7000 miles to get serviced properly. A dealer can always hook you up with an authorised Naim service shop (or Naim themselves in my case). Just a question of shipping fees.

There seems no precise or even vague pattern to the problem, timing wise.  Today troubles kicked in around 11am and again around 2 - 2.30 ish.  Long periods pass without issue, and right now its playing sweet as you like.

The fridge is on all day and has always been there so seems a less likely culprit......  And there's no boiler.  I could honestly be forgiven for thinking the telco had just erected a giant cellular mast right outside the window.  But I can't see one..... ;-)

I can't deny that a service is way overdue, but that would probably require shipping to the UK and back (a similiar distance to you actually).  I think the combined freight & service costs on 'budget' kit this old are of questionable value considering the resale value, although maybe not compared to the replacement cost of more modern gear.  I had virtually resigned myself to buying afresh when this kit eventually died, but had hoped to eke out a bit more life yet.

Its moments like this when I think back to a recent visit to smoky Singapore, where the dealer had an ex-dem SN2 going for about £1,850.  I actually toyed with pulling the trigger (on the plastic), but bottled out.  With hindsight perhaps I should have gone for it......

On the other hand, perhaps there is an external cause after all, which I just haven't traced yet. Hmmm.

Since we are no closer to locating either Where the problem is let alone What the problem is, maybe we can start with a process of elimination. Easiest test first: Can you simply plug the system in somewhere else that is a different spur of the mains rung? Such as a different room or friend's place?

Doubt that is the issue but let's eliminate one thing at a time.

Have to think about how to test the other components with the restrictions you have. Not having the RCA-DIN4 to test the pre and power independently is a drag (assuming another pre and power were available). The age of the kit is still making me highly suspicious. I had a friend with a Cyrus3 amp that had a similar problem - fine 60% of the time and all cracks and pops for the rest of the time and that was caused by dry joints on the solders. He powered it off each night and it had the problem from morning until afternoon when it finally finished warming up.

Maybe some other members will have bright ideas for testing and think of something obvious I have overlooked.

I would be tempted to sell your amps & flatcap, as they will inevitably deteriorate sooner or later, if they haven't already. A Superuniti or a Supernait would be a big improvement - it might also solve your interference problem too, but no guarantees there!

Good luck.

Chris

Feeling Zen, I do have another integrated amp with pre-out that could help with testing (both ways) but still come back to a cabling problem, also lacking the necessary DIN out > RCA, as well as the one you mention.  Living in the back of beyond has its challenges !  I will have to think out the box on how to approach this....

Chris, you are quite right of course.  I guess the only reason I hadn't sold is that the resale value is pretty negligible by now, and its probably worth more to me (working) than to someone else.  That and the fact that (recent issues aside) it sounds way better than it should have any reasonable right to !  :-)

Yes, resale value is quite low, but if you're going to keep them, I would still suggest a service. I once left a NAP90 unserviced until one day it decided to dump enough DC current into my speakers to fry the bass drivers. 

Taking it to a friend's house, as suggested above, will eliminate any mains interference issue. If it's happy at a friend's place, it's your mains and the system is fine. I'd do that as a first step. 

That said, servicing is essential with such old stuff. I once sent a 250 to Naim and the capacitors were so shot that if I'd left it any longer the amp would have taken my SBLs with it. If you cannot get them done, a Nait XS is likely to be better than what you have now. 

Yikes !

That would be most unwelcome Chris, to put it mildly.  The moral must be: sell unto others before it do-eth unto you.  Heh heh.   ;-)  Or take the long road to a service, which still feels uneconomic being honest.....

HH and Feeling Zen,

I will try and take it to a friend's place, I think, as you both suggest -  although the obvious candidate is away for a few weeks.  He may have to do the listening though, as the intermittent nature means you could go a day without hearing it.  But no doubt, this is the best way to isolate/eliminate all external factors.......

25 or more years ago I lived in London and had a 32/160 combination.  I used to suffer terribly from breakthrough from a local (presumably) taxi firm.  Nothing I did would ever get rid of it.

At the same time a friend of mine who also had Naim amps suffered breakthrough from aircraft overhead.  All day there was a succession of messages "This is Flight xxx established at 6 miles out".  (Anyone in Barnes still suffer from this?)

I've never had the problem since moving from London.  But this does suggest that RFI has the potential to be a serious issue wherever we live.  I realise this is not a particularly helpful post but I thought it might be interesting.

ForBarry, yes this still feels to me like some sort of extreme RFI issue but so hard to say.  As for planes and taxis talking to ground control or base via your living room hi-fi, that was damned unreasonable of them !  ;-)  And must have driven you stir crazy....

I imagine that modern day Naim equipment is very well isolated against RFI by design, whereas mine actually pre-dates cellular, and it wouldn't surprise me if someone nearby is using high powered / illegally mod'ed comms gear with the potential to cause all kinds of havoc.

Feeling Zen, I reside in a remote outpost of the Philippines. I know there's a dealer in Manila somewhere but even that's a major hike.  And I'm sure they'd say its a back-to-UK job, although hearing their general opinion on the issue would be interesting.....

Yes that's a good idea Felling Zen, and dropping by Makati is something I can easily do next time I'm in Metro Manila.

As well as see what they have glinting on their shelves....... ;-)

Meanwhile tonight, all is silent (between tunes) and well with the Naim system.  Its playing like a little gem.  So strange really.

Hmmm.  Trouble started again this morning.  But I maybe onto something...... 

Walking past the backyard I noticed the cleaning lady was using an old fashioned washing machine outside.  It struck me how the pulsing noises I've been experiencing seemed similiar in timing to the on-off cycle of the washing machine.  Inspecting its mains lead, it has been jury-rigged to an outlet inside the house with black tape 'joins' rather than a proper extension lead.  Also, there was a trip on the main fuse box this morning.

I thought the Isotec MiniSub I'd tried yesterday would have eliminated mains-borne interference, but maybe not ?  I have meanwhile hooked up a Musical Fidelity amp on the same mains outlet as the Naim and it's fine, but then its a much newer & more modern amp, possibly less sensitive to mains issues.

Later I will re-hook-up the Naim and test the washing machine myself.  If that is the root cause, I just need to fix up its mains lead, and also isolate it somehow.

Any suggestions how ?

It does sound airborne RFI. Do you have a radio that you also hear the interference on when it occurs.

That sort of interference could be down to faulty light starts, faulty motor capacitor or boiler ignition systems. Does it coincide with when your hot water comes on?

Of course if it is airborne, which most RFI is to some or greater extent, then it could be a neighbour up to a 100 feet away or so if bad.. 

This needs to be addressed...

however you can make sure your audio equipment is as robust as possible. A service might be worthwhile. A line having gone high impedance or a decoupling capacitor going open circuit will allow such RFI to cause more trouble than it otherwise should.

Simon

Edit just seen you might have found a possible guilty culprit from a neighbour... Goodluck.. Still recommend the service 

Simon, I know you advocate the use of ferrite chokes. Do you think they could help karlosTT with this type of extreme problem? After all they are cheap enough. Not using them myself I didn't touch the subject but since you are now here...

If it is a neifgbour I expect this RFI to be be airborne, not mainly carried in the mains, therefore a choke on the mains will I suspect have minimal or no effect. (But no harm in trying) Also small chokes are better for high frequency RFI from about 10MHz upwards.

if it is a mains suppressor for a motor or igniter on a boiler, or faulty starter on a fluorescent /low energy  light then there will be broadband harmonics across LF/HF radio spectrum, and almost certainly starting well below 10MHz... Think spark gap transmitter as used in the very first radio transmitter.....

Much appreciate all the pointers, advice, and suggestions above.

Am still waiting to prove conclusively it's the washing machine but my money is now on that.  Seems like too many coincidences.

It is infact our machine but I didn't know it was being used (new cleaning lady), nor had I seen the dodgy, jury-rig wiring before.  This will all have happened whilst I was away for a couple of mths.

I can probably fix the wiring myself and possibly even earth the blasted machine, but if it's the internal motor circuits putting filth back into the mains I don't know how to isolate that.  There must be a way (and I don't have the heart to tell the cleaning lady she must hand-wash !).....

PS Edit:  Could ferrite chokes help with that ?  If so, placed where ?

The points about Naim servicing are duly noted (in particular Simon's re internal vulnerabilities to interference), and I will examine the viability and options for that, difficult as I know it will be.  At some point I know I'll have to make a decision about best use of funds.....

Maybe it's not possible in your house, but a separate mains spur, with its own consumer unit can work wonders for removing mains borne noise and improve sound quality at the same time. We used to get a faint pop through the speakers every time a light was switched on, but since fixing the mains silence has reigned. 

Let's hope the washing machine can be dealt with. 

Electric motors are notoriously electrically noisy and are usually fitted with noise suppression capacitors. Perhaps its the motor that needs a recap. If you search for "electric motor suppression capacitor" you will find plenty of info. An electrician would be the best bet for further advice.

Thx again guys, very helpful info.

The spur concept is one that I'm aware of and kind of thought was in place...... sort of  ;-)  There are only 2 earthed power outlets in the house, and I figured each probably was on a separate spur (although who really knows what kind of mains malaise exists behind those walls).

I'm now thinking the best bet is to find an electrician to look specifically at the washing machine from "all angles".  Hopefully that can provide a short to medium term fix.  I will report back.....