EL84 Amp
This amp was based on a Pilot schematic I found on Ned Carlsons web-page (www.triodeel.com). The input stage was "stolen" from that schematic, and I added my own output stage and powersupply. The amp uses push-pull EL84s and an ECC82/12AU7 in the input stage.

I was looking for a simple and cheap circuit to build, and I chose this one because I already had most of the parts. The circuit of the amp is shown below. My prototype amp hasn't got any feedback, so Ry, Cy, Rf, Cf and Cx is not used. I built the prototype with a 40W Hammond 6k6 transformer (because I had it). Later I have bought a couple of used 8k transformers. When I finish the final stereo version I plan to add a bit of feedback. The amp actually sounds fine without feedback, but the bass is a bit "boomy".

To be continued...
EL84 Amp, top view

EL84 Amp, bottom view
How NOT to build an amp?

EL84 Amp, schematic

The powersupply is simple and cheap. The transformer I used was from an old scrapped PA amp. A standard isolation transformer and a separate filament transformer is another cheap solution. That only works in 230V mains countries of course. The powersupply shown is for a stereo amp.

EL84 Amp PSU, schematic

High resolution schematic for printing


Comments? Questions? Just send me an e-mail!

MailMail: mcs@post5.tele.dk