Valves Amplifier Upgrade

This Documents describes the upgrades i did to a push-pull amplifier i built from a kit.

© 2012 - Alessandro Malanca.

It was an upgraded Williamson circuit with ultra-linear connection. I Started changing it back to the original Williamson circuit. Then decided to changed valve working parameters to meet the nowadays produced specifications. Connected final valves as triode. Removed the inductors to have fast transient response.

Practically it has a parallel single ended transformer driving. This kind of connection it is not a push pull: the current driven by one valve is given by the other one. In this configuration no noise is injected to other stages through power supply. It needs no feedback at all ! Just connected the wire for joking !

I have never heard something to sound like my amply !!!!

Power amplifier

V1 is a standard totem-pole input stage. Signal is taken straight and inverted to drive V2-1/2 and it has a standard centered bias (not a push-pull). The V2 normally drives the the V3/V4 output stages connected as Triode. The transformer by itself naturally inverts one of the valves so we have parallel transformer driving. I have a setup with almost no feedback.

Valve bias

Simplified and capacity removed.

Here is how it should be but i have no time to work on it !.

Power supply

Filaments DC powered. Bridge replaced (wrongly designed) and stereo channels separated.

Pre Amplifier

The original amplifier is completely redesigned. I use 2 parallel Ecc83 single ended straight driving.

© 2012 - Alessandro Malanca.