Re: SET tube amp and blowout?

"Paul Moore" <paul.t.moore@xxxxxxxxxxx> wrote in message
news:UPudnTD-p-Jsd-DenZ2dnUVZ_sednZ2d@xxxxxxxxxxxxxx
> Knowing that most speaker blowout is caused from low wattage amps
> distorting the signal

Huh? No, speakers blow from exceeding ratings (note that most speakers
rated "RMS" are damned if they can handle even half that, in real watts!).

> what is the likelihood of speaker blowout on SET
> amps? And is there a way to determine a "red zone" for speakers when it
> comes to harmonic distortion and wattage?

You could add a circuit to detect when the output tube's cathode current (or
grid voltage) starts drifting, coincident with drive signal peak coming near
0V (when the grid goes positive, it pulls current from the cathode and a DC
voltage appears on the grid leak resistor, shifting bias). Or a peak
detector when grid voltage peak approaches say, -5 to -1V with respect to
cathode.

But that's useless, because it'll sound like *** by the time you reach that
anyway. Consider music that has a dynamic range of 20dB: that means, from
an average low level of say 0.1W, you have peaks up to 10W. This might
barely be acceptable on a 5W amp, since the peaks are getting clipped only
3dB, for a dynamic range (at the output) of 17dB. If you want to play it
twice as loud, you just crunched your headroom to 7dB and it *will* sound
nasty (especially on bass, which needs a lot of power to register the same
intensity as midrange, and especially on peaks, which need a lot of power
for only a short duration).

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


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