Building the AX84 Amplifier

I had planned on building a small tube amp and the AX84 project came along at a good time. It uses a single 12AX7 in the preamp section driving an EL84 power amp running single-ended class A configuration. I used one of the Princeton SE output transformers that is like the Champ tranny but more heavy duty.

The cabinet was built to hold a 10" speaker. The pine surface was finished in glossy polyurethane and the front speaker board was finished in matte black.

I built a cabinet for the AX84 out of solid pine boards. It was sized to hold a 12"x8" Hammond steel chassis. As you can see from the picture, it was mounted vertically with the open bottom to the back of the amp. After some consideration, I decided to cut the chassis in half so that it was 12"x4". The half that was removed can be used for another amp. When the back plate is put over the chassis, the bottom is open which allows plenty of air flow.

The pictures below show how the chassis was cut in half. The components were mounted on perfboard and wired point to point. The power supply section was built on terminal strips. The tube sockets are bolted to L-brackets and screwed to the metal box so that the tubes are vertical, pointing down. The EL84 is on the left. The power and output transformers are bolted to the back side of the steel chassis.

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