[patrick-turner]

Phil mentioed......A test CD will give you that plus standard conditions for burst frequency, length and repetition rate.
None of which matters one a HOOT to a hobbyist audiophile.
Cos he can use music programme and a scope to see what is really going on.
..... Phil

Yes, music can show wat's sort of happening a bit, but then music's dynamic range varies hugely between say busy music by AC-DC /noisy punk band, OR something bt Motzart, or Beethoven.

I've sometimes used pink noise to test audio tube amps. The bandwidth of this noise as a test signal is important, and if you use DC to 25kHz with a tube amp, the very low F content causes mahem due to OPT core saturation because of F below 20Hz - unless the amp has sufficient bandwidth limiting with HPF C&R and input and between stages. The maximum power output of the amp with a sine wave is handy to know, and useful for engineers, but for hi-fi amps its an almost useless figure because the max PO can be deemed to be reached when the highest peaks in music are repeatedly just beginning to cause clipping. So The dynamic range within the pink noise becomes relevant, and that range is never infinite. But let us sippose we limit the pink noise bandwidth from 20Hz to 25kHz using simple R&C filtering, and then include a pole at 10Hz at the tube amp input, then the occasional LF signal at max amplitude of unfiltered noise will probably not cause much **** to hit fan in OPT. And the **** to fan noise can be heard as an irregular "knocking noise" coming from the OPT. Tubes don't like it because during the "knocks", they are momentarily saturated, and with grid current and there is charging up of coupling caps, so intermittent class A operation and paralysis.

But one can get a fair idea of maximum PO possible with pinknoise using a CRO by getting some slight clipping to occur, and setting the trace amplitude while clipping to the full height of graticules. A clean sine save of 1kHz from a sig gene can be used to find out what Vrms voltage is needed to get the trace swing, and so then you can determine the sine wave needed for clipping of an intermittent signal with similar character to music. In a class AB amp, usually yhr pink noise clipping voltage is more than if you have a CW, understandable because of PSU rail sag.

Most levels used by most audiophiles most of the time do not make the rail voltages shift at all, even with very low bias current in tubes and with load matching that gives a small amount of class A PO as a % of the total AB PO possible.

If one wanted a burst maker I guess one might use a 2 transistor multivibrator that makes LF square wave control a couple of solid state switches. One might then be able to vary the square wave timing, ie burst time, which seems important if 50Hz is the CW frequency, and one wondered what the performance is like with so much R&C coupling and OPT coupling present.

I've got a home brew pinknoise maker, and its all I seem to need. Another way is to have a simple mute switch to reduce input -20dB, and just flick it on-off. This is rough, but you can get an idea between what happens with CW or intermittent bursts because rail sag and recovery take time. If fact there should be considerable time because of large size rail caps. The behaviour also needs to be known for both clipping and with say +20dB input overload, and the recovery from this. Nothing should smoke.
Patrick Turner.