Gareth Magennis wrote:



The result of which is all the secondary HT voltages are reduced by around
20%, BUT, so is the heater supply voltage.
In this case dropping from 6.1v to 5.1v.

I'm no expert in valve amp design, but this seems to be rather a strange
design choice.


** The same idea was used by MusicMan in several models to create a half power switch.

I did a quick test on a few 'X7 and 'U7 types and found good operation was maintained to under half voltage on the heaters. At about 2 volts instead of 6.3V, voltage gain is low or sub unity.


..... Phil