I wonder if I might pick the brains of some of you illustrious gentlemen

Flattery will get me everywhere, yes?

Anyhoo, on to the question.

I have an NAD S300, as some may have gathered from previous posts. It's currently with Lenbrook being fixed coz it's busted.

Thing is, I still don't know how it got broken, and I don't want it to happen again due to my ignorance.

I don't do anything untoward, don't excessively crank it up, have no children and the spouse is scared to death to go near it so it's none of the usual suspects. My speakers are an easy 8ohm, 93db/Wm and the amp can provide current by the bucket load anyway. It's got loads of breathing room, so it's not a heat problem (though it is a hot running amplifier).

I do have pretty crappy mains, but I don't think this would have such a dramatic effect, would it?

I am currently using Kimber 4PR speaker cable (needed to increase length but had little budget to do it on), and a little birdy has told me that some amps don't like it because of it's high capacitance - it makes them unstable. Any clue if this is applicable to the S300, or NADs in general?

The symptoms are:

Initially:
Intermittent static on the right channel only

Got sent into workshop, and sent back without being fixed.

This developed to:
Again intermittent, the static would come and increase in volume until a loud pop (if I hadn't leapt for the off switch in time). Some form of feedback, yes?

Finally:
The amp got mightily annoyed that it hadn't been fixed the first time it went to the work shop, and just switched into speaker protection mode and sulked. It wouldn't come out.

Now the nice man at Lenbrook has replaced a four transistors (two in each channel to maintiain component balance) and it's working fine (alledgedly - I've not got it back yet).

 

Borrow or buy something like Naim NACA5, Linn K20 or DNM Reson and see how the amp likes that. You're in a Schrodingers Cat situation - you daren't use the Kimber on the repaired amp in case it breaks it like last time.
If it's okay with a low capacitance cable (all of the above) and you don't feel the sound is excessively compromised, all's well.
You could always ask the repair chap?
Simon

 

hi,
i think nad's are pretty tolerant about speaker cable but the people to ask are nad themselves. they'll be able to give a definite answer however if nothing is mentioned in the manual then it's usual to assume that there is a zobel network for the speaker outputs which normalises the impedance and capacitance 'seen' by the amp. some manufacturers such as naim leave this off as they believe it degrades sound quality hence their fussyness about cables. horses for courses really.
You could also ask russ andrews or kimber if their cable is suitable for use with your amp.
the increasing hiss and pop sounds to me (and my admittedly meagre electronics knowledge) like a dodgy capacitor - these things do go 'off' from time to time but it usually takes years. you may just be unlucky.
good luck.
cheers


julian

 

Yes, but you'll need your finest tweezers in my case...

 

In case anyone's interested my amp is now fixed. I collected it and had a chat to the engineer who say's I've just been a bit unlucky. He says the S300 is tolerant of all cable types, so that won't have been the problem.

In Lenbrook's praise they didn't charge me for the repair, despite the fact that it went in two months after the original visit (based on my contract with them a month is the longest period they were obliged to honour).

It's been in use pretty much solidly for 5 days now, without a glimmer of a problem.

 

Excellent news. Glad to hear audio normality has been successfully restored for you.