6GW8 one tube amp


6GW8 one tube amp


The 6GW8 is a 9-pin high-mu triode and sharp-cutoff pentode in the same envelope. It is identical to the European ECL86. The triode section is similar to half a 12AX7. Introduced in 1961, it was one of the last audio tubes to be developed before the end of the valve era.

Effectively it is a complete amplifier (preamp + output) in one tube. It produces about 3W and was used widely in 1960s Oz practice amps, as well as radios, stereos, and in a push-pull pair producing 8W, small PA amps.

The other tube in this amp is a 6X4 rectifier. With a diode rectifier, you can definitely make a genuine one-tube amp.

I bought this lovely speaker box and the amp chassis (which serendipitously was a perfect fit) from separate eBay sellers. I saw my chance to build a tribute to the small Goldentone and Electravox amps of the 1960s.

Here is the circuit I used:

I was hoping to use the period-correct Rola 8" speaker with its button AlNiCo magnet, but it wasn't up to the job, so a new Jensen was fitted, and sounded great. Here's a bigger photo, plus a link to a YouTube demo.