Antonio Vernucci wrote:
I'd like to hear someone having tried to use a power transformer as
output transformer for the single-ended final stage of a tube
communications receiver (power 5W, maximum, frequency not higher than
4,500 Hz).

As a matter of fact a plain power transformer with a 220V primary
winding and 6V secondary winding would well match a 4-ohm speaker to a
5400-ohm plate load.

Basic questions:

1) does the DC current flowing through the transformer create problems?
(do proper audio transformers have a gap in the magnetic path to avoid
saturation?)

2) would a typical transformer work up to 4500 Hz, while maintaining the
expected impedance ratio?

3) would modern transformers wound on a toroidal core offer better
performances?

Unfortunately, proper audio transformers are getting scarce these days.

Thanks and 73.

Tony I0JX


A 6.3V filament transformer will work but will be far from ideal. Far
better to take one from an old valve broadcast receiver.

Steve H