Re: Two amps, one set of speakers ...



Karl Uppiano wrote:

So far, my money's on you: your real-world empirical experience trumps the
usual Usenet speculation. (Although I do wonder about that other poster
who experienced real-world arcing in the output tubes of his guitar amp
when the speaker got disconnected ...)

I am sure there are situations where this can happen for some reason or
another -- a poor design, for example, with tubes rated for barely more than
B+ (either by design, or replaced with the wrong types). Or an amp that is
only marginally stable under favorable conditions and begins to oscillate
when unloaded. BTW, the "flyback" behavior of an unloaded transformer might
come into play if there is high frequency oscillation.

No oscillation needed ! You really don't understand flyback do you ? Why do
relay coils need reverse biased diodes across them ? It's the same mechanism. V
= -L.dI/dt

A well-designed, unconditionally stable amplifier with a proper feedback
design should automatically reduce its drive so that the unloaded output
voltage is practically the same as the loaded output voltage. That leaves
only the poorly designed, unstable amps to blow chunks when unloaded, IMHO.
Sort of Darwinian justice, isn't it?

Why do you have such trouble believing this ? Several ppl have told you it
happens. Feedback doesn't work when an amp is overdriven ( the feedback goes
open loop ) and in any event the low feedback used in tube amps can only do so
much to help and some amps ( esp guitar amps) don't have feedback round the
output stage.

Graham


.

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