In article , JustMe
wrote:


Some amps' frequency responses can alter during warm up. Whether this is
a reflection of poor design or the designer's intent is another matter.

I'd be interested to know which models do this, and by how much, and at
what frequencies, this change occurs. Not something I have encountered so
far as I can recall.

One of my favourite amps sounds *very* different when first powered up,
compared with when it's hot, to the degree that a demonstration of it
when cold would not impress me whilst, when warm, I love it.

Again, I'd be interested to hear the details.

I have no trouble leaving it on, so this isn't a problem for me. While I
may be curious as to *why* this is the case, I don't really care that it
is so - I prefer it and that's all that's important.

Well, it does seem like a 'problem' to me as it implies that the
performance will drift about with room temperature, variations in the music
power changing the temperatures of devices, etc.

KH in a recent issue of Hi Fi News did do some measurements that showed
that the distortion levels in some amps vary as they warm up. However
others don't do this. My recollection is that this has been a 'known'
possibility for decades. (I certainly worked on it when developing over 20
years ago!) Hence such things should in general be removable by correct
design in my experience. If the set sounds 'better' when 'warmed up' then
I'd prefer the design to give the 'better' performance almost from the
instant of switch-on. Not to have to leave the set on for a long time
first. Partly as this would be a minor irritation. Partly as, to me, it
seems like a sign that the designers have not investigated and tackled the
problem.

Slainte,

Jim

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