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Naim Help

bigtall1

bigtall1

Member
Hi all, I need some help and advice on my Naim system. I have a NAC 72, NAP 140, Allae speakers, Rega Planar 3 currently with an Ortofon cart.
The other day I was listening to some vinyl and I turned the volume up and something went wrong; I still have sound out of both channels but it is muffled and not sounding good. I swapped my Goldring cart to an Ortofon which has made no difference to the sound. I had the NAP 140 serviced by Darran at Class A about 4 years ago now so am guessing it's not that. The NAC 72 has never been serviced since I bought it 4 years ago so I think this could be the issue. Any advice gratefully received.
 
Could be the preamp. I would also check the cabling, power it down, disconnect everything, give it a thorough inspection, and if it all looks good, reassemble and see if anything changes. What speaker cables are you using?
As nobeone says, if you can try a different source and preamp input, that will help to pin it down.
 
The case is easily removed from the 72. It's just unscrew the four feet and carefully slide the case off. You could have a visual check that there's any leaking or burnt components (blackened or white stuff from caps). In fact, while you're at it you could slide off the boards and slide them back on again to their posts. If you google Naim 72 you'll see pics of it without case, and it's just little boards which slide on and off gold posts. They might just be loose.
 
There aren't any failure modes I can think of that can cause bandwidth limitation like this except for tweeter damage, especially as it seemed volume dependant. I think we can rule out the amp because if that goes wrong it's usually DC on the speaker outputs. An unstable amp could be the culprit as 250's can do this but I'm not aware of any 140s doing that - and it's been fine since Darran serviced it.

Start with the source though, we know it may not be the cartridge, but are the other inputs working correctly?
 
power hi-up?
- NAP140 with NAC A5 speakercable > maybe tweeters from speakers?
- with other LScable than A5 > maybe NAP140 poweramp?
 
If it is the Alaes it might a good time to upgrade as that’s a great little system you have there and would really benefit from some other speakers.
 
In addition, I see no mechanism where a fault in the power amp (or pre-amp) would cause the fault described by the OP.
 
/\ yep. The OP says " I turned the volume up and something went wrong"... almost certainly blown tweeters caused by not enough power... yes not enough power! The amp clips the waveform when it runs out and generates high frequency distortion (above hearing usually) which all goes to the tweeter. The speaker may be rated for say 100W but that's averaged over a range of frequencies and takes account of the fact that most of it will be handled by the bass/mid unit... the tweeter alone may handle as little as 10W. It's the most common cause of blown tweeters...
 
Arkless Electronics said:
I noticed you mentioned this in another thread.... power cuts do not cause damage to anything. Lightning strikes do!
Click to expand...
True for linear power supplies, but a sizzling power phase browning-out on overloaded Edwardian power grid in Central London can be guaranteed to take out as many SMPSUs as you can count. I changed many little bootstrap caps that day!
 
MJS said:
True for linear power supplies, but a sizzling power phase browning-out on overloaded Edwardian power grid in Central London can be guaranteed to take out as many SMPSUs as you can count. I changed many little bootstrap caps that day!
Click to expand...

OK I guess with badly designed SMPSU's that could happen but that's a brown out (and many SMPSU's are specced down to 90V) not a power cut.
 
I have mentioned this before but you are most likely to blow your tweeters with a low power amp rather than with a high power amp through clipping as Jez mentions above. Speakers are voltage driven and if the wick is turned up too high as is sometimes the case with parties the amp is driven into clipping and that generates an effective square wave into the speakers. Now a square wave contains all odd frequencies up to infinity so energy that may be say in the bass (and this is where most power is needed) a lot of it is turned into higher frequencies that enter the HF crossover thence into the tweeters. Exceed the maximum power rating of your tweeters for a short while and they fry.

Cheers,

DV
 
Arkless Electronics said:
I noticed you mentioned this in another thread.... power cuts do not cause damage to anything. Lightning strikes do!
Click to expand...
Bit of a generalisation, they play havoc with my alarm system. It was probably entirely coincidental re my nap 250 as it was probably a good 7 years since it was serviced.
 
Try unplugging the bass units on the back of the speakers (having muted the preamp). Then play some music and see if the tweeters are still working. If not, they have blown. This seems the most likely reason for the problem.
 
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