Amp Zero

This is my first attempt at building a guitar amp from scratch. The design is heavily influenced by the Gibson EH-150 of 1936. I've always though that the combination of a 12" speaker and push-pull beam power tubes provides the essence of ampness. This thing has those, and little else.

The cabinet was my first attempt at woodworking. I bought the $20 router from Harbor Freight and used it for cutting the wood to size, cutting the speaker hole, rounding the corners and making all the slots for the joints. I did a pretty crummy job so there are animal tracks all over the amp, but most of them aren't easily visible. I was astounded when the cabinet actually turned out to have fairly square edges and sat pretty flat on the ground. I got some perforated metal for the speaker grille, like the EH-150, as well as the decorative floral speaker mounting screws that were popular on the early amps.

The schematic is mostly EH-150 with the addition of modern components and subtraction of ancient components. There are no electrolytic capacitors in the entire amp. Filter caps are 22uF plastic caps, cathode bypasses are 10uF plastic.

I'm still messing with the circuit, mostly trying to get the driver transformer scheme to work better and reduce the hum and noise.

How does it sound? Pretty good. It's a one knob amp, so you don't have a lot of tone options and it doesn't have the "fender notch". It doesn't have tons of gain and only puts out about 10 or 15 Watts, depending on how I have the driver and output stage biased (I'm working on it). But it can get pretty loud. It's definitely not just a practice amp.

The Amp

The Guts

Schematic Diagram of the Amp

Back to Amps