When doing tests, most tube designs do show greater dynamic headroom
(which is different from dynamic range). Headroom is instantaneous
power--like bass drum and gong whacks. Perhaps the greater complexity
of the transistor circuits are a limitation. I do know that most, but
not all, transistor designs have more loop feedback because a transistor
has more open loop distortion than a triode (I don't know how an FET
would compare to a popular output pentode like an el34 or kt88).
Perhaps the greater number of stages and complexity in a transistor amp
causes it to fall apart at the limits. I don't know. Perhaps one thing
to consider is that tubes are thermionic devices and behave nothing like
transistors. Perhaps the tube, since it's absolute maximum limitations
can be exceeded momentarily, are just able to do 110% (like something an
athlete would say). The maximum ratings on a tube can be exceeded
without destroying the tube. Yes, the tube will wear out real fast, but
it won't catastrophically fail like transistors. If you over-current a
transistor, then POOF, you release the magic smoke and no more
transistor. One of the reasons the military and FAA kept tubes around
until the early '90s was that most tube electronics aren't destroyed by
electromagnetic pulses (EMP) from a nuclear explosion. The only way to
destroy most tubes is excessive heat/current. An over-voltage that
lasts for a microsecond won't pose that much of a problem for a tube
circuit--it just soft clips. There are all kinds of losses in a tube
design that make it more forgiving. All things being equal, I'd rather
record or reproduce with tubes because they compress instead of
distorting in the gross way a transistor will. I think the reason I
prefer tubes is that you don't need as much feedback for acceptable
performance, which means superior TIM numbers, something I think I can hear.
Bob Olhsson wrote:
> -----Original Message-----
> >From Steven C. Barr: "Nevertheless, since virtually all home-use audio
> equipment does have SOME
> distortion, the "warmth" of tube-amp distortion DOES exist...and is easily
> audible. This is why many guitar amps still use tubes (although, admittedly,
> the users of such amps often deliberately SEEK distortion...!)...
> Also, I'm curious...does the average home tube amp have the increased
> dynamic range...?"
> I can't speak for contemporary equipment but the older stuff definitely had
> a wider dynamic range and this resulted in a more "effortless" quality that
> a comparably rated solid state unit. If you measured from the noise level to
> the 5% harmonic distortion point, the tube gear generally came out way
> ahead. It looked worse if you measured between the absolute noise level but
> restricted distortion measurements to a few tenths of a percent.
> Bob Olhsson Audio Mastery, Nashville TN
> Mastering, Audio for Picture, Mix Evaluation and Quality Control
> Over 40 years making people sound better than they ever imagined!
> 615.385.8051 http://www.hyperback.com