Hifi, why bother?

[Mike Watterson]

Good point - Mike's "EL84" could be another valve, remarked. Which would explain it looking like a BT.

It couldn't actually be a 6BW6, because the pinout is different from EL84. Unless... it not only had the 6BW6 guts, but was then pin-connected like EL84 before fusing the envelope on and sucking out the air. In which case, the deception was obviously intended at the factory!

Though, if that was the case, I'd rather like one to do a trial swap...

I didn't examine the valves closely at all. It was definitely labelled EL84. You can't easily see the construction of an EL84, certainly from the top due to the mica support.
https://www.radiomuseum.org/tubes/tube_el84.html

Amie, the 6BW6 is maybe more like 4W to 4.5W and the EL84 about 5W to 6W (both optimistic Class A actual output power. The EL84 might give nearly 20W class B push-pull as the dissipation is a bit over 12W. ). The Audio transformer was certainly smaller than most valve radios. It seemed like a mad Guitar amp. The spring line reverb was just like in an old Marshall and had open circuit transducers. I gave him an old one from a marshal.
The Octal was certainly a KT6x, but not the big one, the one more like an EL33 shape.

The 6BW6 (noval) is similar to an Octal 6V6, but obviously not the same valve. The B7G 6AQ5 = EL90 was maybe more popular in USA radios and used in some early 1960s smaller German sets. I'm not sure if the 6AQ5 and 6BW6 are exactly the same valve in a different package. They are similar and possibly either can work in a 6V6 circuit with an adaptor.

Anyway my original point was that the amp was an example of fashion and style more than a sensible valve guitar amp that would have been better with 2 x EL84 rather than 2 valves with a changeover switch. Why not even a centre off switch rather than a printed warning not to changeover while the amp is on?

The guitar player eventually admitted that he couldn't hear the difference between the two valves when I said I couldn't. Not as if one was Triodised either!

Edit:
I think the 6BW6 / 6AQ5 are shorter than an EL84?
https://www.radiomuseum.org/tubes/tube_6bw6.html
The B7G version looks tall as the envelope is skinny. It's actually obviously shorter in real life. I have an AEG Bimby with an EL90. Gets hot but not as hot as an EL84!
https://www.radiomuseum.org/tubes/tube_6aq5.html
https://www.radiomuseum.org/tubes/tube_el90.html