[Amps] Checking for IMD

[Jim Tonne]

Tom wrote:

> Also there is a basic flaw with two-tone tests. Two-tone 
> tests don't vary the power supply loading like a voice 
> signal would. Flaws in grid voltage or high voltage dynamic 
> regulation may not show at all. Almost always the error 
> makes things look better than they really are.

And Jim is adding:

Very true!  And if the separation between tones is down 
below, say, 100 Hz, then the power supply regulation (or 
lack of same) starts to enter into the picture.  To test the RF
block alone be sure to use separation of at least 1 kHz.
But to test the entire system we have the dilemma of how
to simulate voice.

How pure does each tone of a tone pair have to be to
check IMD using a two-tone test?

- JimT