wrote:



Another question, should you decide to field, and able,
is what about PURE THD ? I mean pure THD without the noise.
The only way I can figure is to exploit the randomness of
the noise by somehow recording the output and synching it
somehow to get an average reading from a number of cycles.


** Digital scopes can do that job, by averaging a number of screens.

When the scope is synched to the test frequency (using ext trig), it is also synched to the harmonics. So averaging 8 or 16 screens removes much of the random noise and hum.

.... Phil