Testing output transistors.

[miklos]

Strange isn't ,but what would be the alternative, 1dB/Div?
May be the CD+LM4562 source is more believable.
I made a set of measurements with the CD as a source and the result is comparable to the Bruel.

[magnoman]

Miklos,
As a sanity check couldnt you just reduce the source amplitude by a factor of 10?

Thanks
-Antonio

[miklos]

The oscillator is old and pretty unreliable, but very convenient to use it on the bench.
What is confusing with it that the "Attenuator" output using the generators transformer 60 Ohms tap. For the 1W measurements I needed 3 V output and I got it on the 600 Ohm tap, from the "Load" connector, which can produce 40V, so less drive was needed from the gen. output stage, consequently has less distortion to. Anyhow the measurements are good for comparison of the transistors, fortunately the transistors having higher distortion than the gen. Also I can measure the better ones with the CD+LM4562 setup, but it's already clear at the very expensive Semisouth fet is the best, followed by the pretty inexpensive IRF240.