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hagtech wrote:

I did bandwidth measurements at 1W.  ….  I should plot both 1W and 6W bandwidth responses.

I always feel strangely disturbed when I see people specify SET response from 2Hz to 150kHz. Here is a practice out there to consider SET response not at full power and I cannot imagine if could be more bogus measurement then that.  A response of a SET amplifier must not be measured at fraction of it’s powers. Well, one can measure whatever s/he what but those numbers should be never made public. Measuring a SET at 10% of full power is like proclaiming that a car goes 1000 miles per hour, forgetting to mention that the speedometer was calibrated in a way that each mile has 23 feet.

A lower frequency response is a properly of power and inductance. In a complete SET amp, with already made gap the inductance is fixed and plate current driven through a transformer become a factor. So, there is ONLY ONE way to measure true frequency response of SET amp: found max power into a given load at MF and to see where the SAME POWER will have -3dB at bottom and atop. Usually at the bottom 20Hz -25Hz considered incredibly good numbers; very few amps do it and most of the “cheap” SETs do 30Hz and up. Some of them roll of say at 40Hz and some of them clip at 40Hz… I heard the stores how well reputed and expensive amps were measured at 50-80Hz of full power. BTW, when I was saying the LF channel of Super Milq goes down to 7.5Hz I meant that it was full power, or 3dB less than the max amplitude that amp I capable to develop. In HF for full-range SET the 20Hz -25kHz are very good numbers at fool power…

Well, theoretically, if a person knows that his 8W for instance amp NEVER develop more than 3W to the given load then the 3W might be recognized as a reference frequency response. In reality, a 8W amp, ever driven a very efficient load of 105dB, in order to never go over 3W, the amps should be high-passed somewhere at 500Hz. I would personally would like even to have at least 6-8dB of headroom between the max signal/power an amps get from music and the moment when amp’s power max out.

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