Catalinbread Paredoila/brownface fender vibrato

[claytushaywood]

Man I never knew how amazing brownface fender vibrato circuits were.  they really do almost sound like a type of vibrato!!!  is that just such a magical sinewave that i'm hallucinating subtle pitch shifting in the upper harmonics from meer volume changes, or is it actually happening? 

I also heard a tube tremolo project at runoffgroove, it appears they only sell the kit or the pedal for that, as i dont see the schematic on it over there.  it sounds really sick and apparently is pretty low noise, which my pro reverb is not known for. 

what kind of vibrato (or tremolo, or maybe not haha) is that on the brownface anyway?  as in what is it called?  and how does it work?  is that the power tube bias modulation or whatever i always hear about?

[bigmufffuzzwizz]

I do know that it was traced over at FSB..

[jcuempire]

Here's a vero of it from Sabro's site:

http://www.sabrotone.com/?p=2528