The Valve Wizard

Parts for valve amplifiers!

EL84 Power Output PCB

The EL84 power output PCB allows you to build a single-ended or push-pull output stage using EL84s or EL86s, and possibly others too if you know of them. The valves can be fixed biased or cathode biased and there is a dual-gang master volume control (option of course, just link across the pads). Other features include:

Input coupling caps. These aren't needed if you're also using one of my other PCBs which already has output coupling caps, but you may need them if using this PCB on its own for special projects;

Catching diodes between grid and cathode to prevent blocking distortion (described in my book, section 4.19);

Zener diodes across the cathode bypass capacitors to prevent overvoltage (e.g. at startup) and to help recovery from blocking;

Catching diodes from anode to ground to help protect against negative flyback spikes on the output transformer (use 1N4007);

Spaces for stoppers/current-sampling resistors at the cathodes and anodes (I recommend using low-power resistors here so they also act as fuses).

Heaters can be connected in parallel or series (see below).



The issue.2 PCB now has test pads for Rx and Rx, which have also been moved so they are always ground referenced. This is to make it more convenient for adding bias-test sockets for your multimeter.

See the shop page for pricing.