In ,
Jim Lesurf typed:
In article , Jo
wrote:
In , Arny Krueger
typed:


Most power amps already have chokes in series with their output
terminals.
As they should. The Texan didn't.

A snag here is that some designers feel that an output choke
increases the HF o/p impedance and degrades the sound. Classic
example being the older Naim power amp designs which just used a 0.22
Ohm resistor...

... and then may require about 10microH of lead inductance to be
stable. :-)


Yes, this brings us back into the topic of "but can humans really hear the
difference ?" that occupies many threads. I wonder how much extra impedance
is added to the output circuit at audio frequencies by the addition of RF
chokes ? The formula for inductive reactance is simple and for a 100uH choke
I get:

XL=1.3K at 2MHz and 13 Ohms at 20KHz which would seem to be a significant
contribution to the impedance of an amp output circuit...

....BUT if a decent common mode type bifilar wound filter choke is used the
effective inductance in the speaker circuit would be much less than this and
so any degradation of the audio signal would be negligible....or would it
:-)

Jo