really weird tone control question?

[OlAndrew]

So I'm working on this '50s era Magnatone 3 tube job, 6SL7, 6V6, & 5U4. Neat little thing. It's been modded at various times during its history, with varying skill levels in the mods. There's no schematic, that I can find.

The tone control (one only) was disconnected when I opened it up. Now most tone controls that I've seen are either like a guitar tone, a rheostat in series with a cap to ground, or amps where the resistance of a pot is in series with the cap to ground and the output is off the wiper, like a voltage divider volume control.

This one had one leg of the resistance to ground, and the cap connected between the wiper and that leg. I THINK the input was the other leg of the resistance. Seems like this would put a variable resistance across a constant capacitance which would vary the cutoff frequency of a filter?

Anyone ever seen anything like this ? Maybe in an old radio from the same or earlier era? Maybe have the input on the wiper too?

I've rewired it like a guitar tone control, for the time being, just to see if the thing works at all. (At the last minute I discovered I was out of, and needed, 1.5 amp fuses. We'll see what happens this evening after I get some)

Any ideas?

[andrekp]

That sounds like it would work about the same as a guitar tone control. As the wiper moved up the resistor, it would just shunt more and more higher frequencies to ground. Not sure how much diff it would make that the other half of the resistance is in parallel with that cap. I think the signal would largely ignore it.

If you're not heartset on keeping that, I'd just put in a nice single knob tone control like the tweed style, marshall style, etc. It'd probably be more effective than that, no matter how it works.