Tube Placement Question

[Mick Bailey]

I think the rules may be optional on Hifi stuff but IME higher gain guitar amps need all the help they can get!

Agreed - I've built hifi amps with very close tube spacing without any problems, though the phono preamp has always been separate.

I was thinking this would be a Magnatone 109 type build with the suggested tube compliment, using a 6SL7 in place of a 12AX7. Not sure how well it would work in practice, though.

[mozz]

1 6sl7 driving a split load PI may not be enough gain.

[Mick Bailey]

That's why I though of the Magnatone as its self-split.

[mozz]

Odd setup on that Magnatone 109, if it gets you more gain i may have to try that one day.

[Mick Bailey]

The circuit would need some tweaking of preamp resistor values, but if the 1st cathode resistor was bypassed the gain may be sufficient using a 6SL7. Depends what sort of amp the OP wants, but a single preamp tube will limit choice somewhat - more tweed era than anything else. Self-split is lower output than using a PI, though.

[catalin gramada]

6sl7 work great with 220k on plate, same gain as 12ax7 with 100k. One gain stage and one cathodyne inverter. You may boost the input with a pedal in front anytime.

[loudthud]

A always wanted to build basically a Champ with two or three 6L6s in parallel and one of those big Hammond single ended output transformers. Keep the B+ low, around 300 to 350 Volts.

[Mick Bailey]

Laney made a 50W SE amp with 5x EL34s in parallel - the L50H. That needs a pretty hefty OT, too.