"Jim Lesurf" wrote in message
...
In article , Iain M Churches
wrote:
An initial investigation of my 50W amplifier which has the first and
second stages DC coupled, shows -3 degrees at 10Hz, and -8 degrees at
50kHz. So about the same as the Audiolab 8000P, and very close to the
Spectral? Not too shabby:-))

Are the above values with an 8 Ohm load from an 8 Ohm tap?

Yes, they are.

If you are concerned about this, I'd suggest you also check with reactive
and/or mismatched loads.

Not so much concerned as interested:-) The figs in themselves do not mean
much if I have no yardstick - hence ther question.



The figures you quoted
look - in themselves - perfectly respectable. Hence unless your amp has a
particularly high output impedance

The damping factor is 20, which for a valve amp very respectable:-)

and/or is reactive at HF/LF I'd doubt
this matters compared to the way most speakers and rooms will affect the
phase of what reaches the listener. :-)

Understood.

This amp has custom-designed Sowter transformers. A similar amp with
Hammond iron may not perform so well.

Since you are doing this, I'd be interested to know the complex output
impedance you get across the audio band as this seems to be the kind of
measurement that rarely gets done and published for *any* amp these
days...

Can you suggest the best way to ascertain these figs?


Iain