funky Supro Thunder I Reverb amp: how does it work?

[Jef]

While comparing some reverb circuits I stumbled upon a schematic of this funky Supro amp with a reverb circuit driven by the OT.

http://www.schematicheaven.com/barga...r1_reverb.pdf"

EDIT: I can't get the link to work, but as you can see, the schematic is on schematic heaven in the "bargain bin" section, Supro amps, Thunder One Reverb.

I think it’s quite interesting but with all those local feedback loops going on I can’t really figure out how it works. Can someone explain to me how the signal flows in this amp?

Thank you very much!

Jef

[Enzo]

The top row is the conventional amplifier, speaker connects to the output tranny on the right. The speaker output was a handy thing to drive the reveb pan as well. So they tapped off the speaker out and drove the pan with it. The lower row is the reverb amp. Also pretty conventional, although it faces left instead of right. It lacks tone controls. It amplifies the pan output and drives the second speaker. So there is a dry speaker and a reverb speaker.

If you want to turn the reverb off, instead of having the reverb speaker sit there idle, the switch selects a tap off hte main amp just before the phase splitter, so the reverb speaker becomes another dry speaker but with its own power amp.

I don't see how the local feedback loops would affect the reverb at all.

SO that is it, the main amp is straightforward left to right across the page, and the reverb has ists own speaker and amp. The pan being driven off the main speaker output. The trem is classic bias wiggler.

[Jef]

Thank you very much, Enzo! Is it possible that the reverb switch is labelled backwards? (on the schematic it is shown as "on", but connected to the tap off the main amp as you describe).
I wonder how an amp like this would sound. I usually have reverb between my guitar and amp, not after the speaker.

Jef

[Enzo]

From your point of view, yes, the switch is labelled backwards. I never even looked at the label, I just saw what it did.

Forget for now about the speaker. The reverb isn't after the speaker in a sound sense. You can tap into the signal path most anywhere. The signal level at the speaker terminals was a convenient level for driving the pan. They could have tapped in someplace like before the phase splitter, but then they would have had to add a tube for a driver stage.

You want to know something that is similar? Powered subwoofers. You run the output of an amp to the sub on its way to the main speakers. The sub takes the speaker level signal, then amplifies it for the sub speaker.