Re: What a sad excuse for a group this is...

In article <476FD0F1.D82BD82E@xxxxxxxxxxx>, Eeyore
<rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:


Aside from incompetently designed amplifiers that oscillated with low
inductance cables (was it Naim ?)

More precisely, the problem was that the amp(s) tended to oscillate with a
capacitative load of a given order. Low inductance per length cables tend
to also have high capacitance per meter. They also make it easier for the
amp to be affected by load (loudspeaker) capacitance.

It is easy enough to avoid the problem by a mix of sensible amp design and
the simple use of a series inductor. But the Naim amp(s) in question did
oscillate into some capacitative loads. So simply using some cables caused
problems.

The amp(s) would be OK if the total load did not look like a suitable
capacitance at HF. The simple solution would be to fit output inductors if
you want the rest of the amp design to stay the same. But that might look
like you'd not made the amp stable in the first place perhaps didn't know
what you were doing... :-) So the 'solution' was to tell people that
'high inductance' cables of at least a given minimum length were needed and
that this 'sounded better'. ;->

IIRC This all surfaced when Monitor Audio started selling interwoven cables
with a claimed 'low characteristic impedance' - i.e. lots of capacitance
per length and low inductance per length. I was told that Naim amps started
going off like firecrackers when people used this. But I haven't
experienced that, although I have in the distant past watched on a scope
bursts of oscillations from an old Naim amp when used to drive a load
without having a length of cable inductance to protect it. Indeed, I think
I also saw the problem with the MA cables IIRC. This was discussed in the
trade at the time, but for some reason never appeared in the magazines...
:-)

Wasn't listening at the time, but it would not surprise me if the results
did 'sound better' when the oscillations were stopped. 8-]

I assume/hope, though, that later Naim amps did not do this, and that
lessons were learned, even if never acknowledged in public!

I wonder how much of the wine tasting of 'cable sounds' grew out of that,
written by reviewers who had no idea what was happening. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Audio Misc http://www.audiomisc.co.uk/index.html
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
.

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