Peavey Stereo Chorus

[liagasg]

I've been trying to figure out the relay/switching stuff in this schem. I cannot really figure it out, so any help would be appreciated.
I m trying to figure out the signal path. I m not interested in the reverb or chorus sections. I do understand the way the signal goes from the input to the op amps until the EQ controls. Presence/level/high/mids/low.

Then there are some switches (the bright is a filter so it's no problem) the there is a Switch 2A and 2B with the 2N3904 and the J174 that go to the input of the high gain channels.

Ican't figure out how/where the signal splits from Clean preamp  and goes to the High Gain pre amp. The tone controls do not affect the Crunch / Ultra channel. They have their own EQ.

Any help in understanding this relay switching would be great.
Schematic is here
http://www.sendspace.com/file/drx4bb

[teemuk]

Ican't figure out how/where the signal splits from Clean preamp  and goes to the High Gain pre amp.

It never splits.

The switching just toggles some additional parts in the circuit by closing their ground reference.

Think of this simple example: There's a single signal path shunted by two clipping diodes. There is a switch at the other end of the diodes which either connects the diodes to ground or disconnects them. Now you could label the switch positons "Clean channel" and "Overdrive channel".

Now think beyond diodes and you start to see how the SuperSat design works. The signal never splits because there are other ways to achieve the same processing effects.

[liagasg]

My problem is that i cannot identify the way the signal goes from the input jact to the inverting input (+3)of the U2A.

It's supposed that when crunch channel is ON, the "presence/lo/high/mid/level" has no effect.
Where (or what diodes) does this take place? Can you point it out?

[teemuk]

Look at S2A:

First half of the switch either connects Presence pot's wiper to node at R28, or alternatively the node at R28 bypassively shorts the presence and tonestack circuits and connects to node in between capacitors C7 and C8.

Second half of the switch provides ground reference for either level and bright controls OR practically for the whole SuperSat gain/clipping stage. Whichever ground connection is left open disables the related circuitry.

[liagasg]

Many thanks, I got it now

But what about S2B? Does it has to do with the J174 in play or not? What I've checked is that these are P channel switching fets. Do they have to do with the signal chain or not?

I cannot figure out the "to remote switch jack". I guess it's the switch for the foot controller.

So when the clean preamp is selected, the signal goes from C7 to Q2 and of to the 1lug of the remote switch.
If the S2A is engeaged, the tone stack of the clean preamp is left out, the signal from U1B (out 7) goes from C17 to C8 & R46

[teemuk]

I cannot figure out the "to remote switch jack". I guess it's the switch for the foot controller.

Yep,it's a connector to which you would plug the coord going to the foot controller. Unfortunately the schematics do not cover what's inside the foot controller. One can make educated guesses on what it does based on how similar footswitching schemes usually work, though.

FET Q2 shunts the signal path to ground so it definitely performs somekind of muting function. Since the FET's gate is effecticely controlled by the same circuitry that also provides ground reference for relay S2B all strongly suggests that this is similar, if not identical, scheme as Peavey's usual "clamping" that shunts the signal path to ground (effectively muting the signal) for a short period that it takes for relays, FETs or other remote-controlled switches to change their state. The purpose would be to eliminate the "pop" noise that switching could cause, which might be extremely annoying especially in high-gain mode.