I assume that you want a lower figure in general but the amp still needs some load… (I’m using 4 Ohm speakers for example)
The amp need to see a minimum inductance of 3.5uH per channel to be stable. Optimum is around 5-10.
That would suggest that my 4m SL cables are not stable. They sound stable to me. It’s most confusing.
So forgive me lack of knowledge, can I assume that for every metre you have of cable per channel this figure acts as a multipler e.g.
Cable inductance is 0.74uH per metre. I need approx 5m to be inline with your 3.5uH.
I’m on!y going off what Naim recommend. It should be in the FAQs somewhere.
But the question is, is 0.74 per positive and negative wire, so in affect a single channel is 1.48. This could mean that you only need approx 2.2M per channel with SL to be stable and in-line with your 3.5uH figure.
I agree, but SL is around 25% less inductance than the NAC-A5. That is a big difference comparatively, so that really doesnt answer what the acceptable ranges really are according to the output design.
It would of been far simplier to say: Within this range e.g. 0.3 to 1.4 is OK providing that you have meterage of xx (hypothetically)
My underlining suspicion is, this means you have to buy Naim LS to be “safe” but not “better” according to materials, insultation, etc
No that is not correct, you don’t double up pos & neg.
The review said it measured loop inductance which is the correct standard,
I just wonder if Naim agree with that result & what method they used.
Whatever the 0.74uH/m is more than the average inductance & as the amps have all moved on over a few design cycles since the first days of NACA4 & 5, I wonder how important the 3.5uH per channel actually is these days
Yeah, I asked support and got a very unhelpful answer. I just want to know if these cable specs meet the amp design spec or not. Surely they know what is inherently stable and what is not. I’m not asking will it sound good, just im not going to blow the output stage!
That was a 7m cable and they measured all of it not just a metre so inductance seen by the amp was 5.18uH, I’d take a guess a 3m pair would have a different specific inductance so as to provide enough for stability.
With the inductance it will reduce linearly with cable length, so whether you take the loop inductance or single cable inductance, a 5m length will be 5/7 of the inductance of a 7m length.
Similarly the capacitance reduces linearly with length so a 5m length with have 5/7 of the capacitance of a 7m length.
The exception to this would be if a cable manufacturer slugged the values by putting fixed components at one end of course.
Best
David
With NACA5 Naim I believe state a minimum length of 3metres per channel
3.5m per channel. See the forum FAQ for more info.
I stand corrected Richard thank you, it’s in my user manuals but my recollection was incorect
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Managed to pick-up some SL on ebay - 7m length (not come yet). Anyone know what guage / diameter the wire is? I need to run it through a floor cover.
Wouldn’t it be great if there was no inductance of capacitance, and then everything would become a known known. Fortunately there are frequencies where this happens (the LCR resonance)…which for the NACA5 is circa 710MHz.
BTW…the nefarious effects of certain speaker cables are more than an urban myth. A friend of mine hooked up some 20 foot lengths of Cardas Golden Reference speaker cables to his 500. That then proceeded run EXTREMELY hot (you could not touch the heatsinks without fear of burns) and the sound went decidely off. The combination of high capacitance and low inductance cheerfully tipped the 500 into ultrasonic (possibly RF?) oscillations. Had he not swiftly removed the offending cables, his 500 would not have survived very long. Running this amp with exactly the wrong cables is like running an engine without oil…it will run (badly)…but not for very long before it self-immolates.
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I managed to do something similar with my NAP250.2. I had Kimber 8TC on a big tube amp I was running at the time and so wanted to see how it worked with the NAP250. It got hot - very hot. And the sound was, as you say Ron, decidely off. I quickly switched off just in case the worst happened (although I guess the thermal trip would activate). The worst thing was that after that little experiment, I was never convinced that the NAP250 sounded quite right. When I did eventually get around to getting it looked at by the service dept., it came back sounding much, much better.
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