How to do individual reverb pots in two channel amp?

[M Fowler]

The Soldano Lucky 13 50w amp, Mike says it is a JMP Marshall in one channel and Fender Twin Reverb in other but each has it's own reverb pot only the presence is shared between the two channels.

Got a schematic? How do you do that?

[DonMoose]

One way is to have the reverb recovery stage feed two series switches (LDRs, probably), each of which drives the WIPER of its channel's reverb pot. You then tie the CW terminals together to sum them. This approach minimizes interference between the two pots.

Where you take that signal next is kind of an open question. Before each channel's master, I would think. The modded-to-death Yamaha T50 I had for a while put them straight into the PI, where they totally overwhelmed the preamp outputs if they were even a little bit on and the masters anywhere lower than 7. Took a while to undo all that butchery.

Hope this helps!

[M Fowler]

Thanks Don I'm still trying to envision all this.

input, bright sw, V, B, M, T, Rvb clean channel

G, B, M, T, Rvb, Vol JMP channel

Presence

[martin manning]

Can both channels be used at the same time? If so then perhaps the channel mixing for the wet signal is done prior to the reverb driver, with a pot for each channel.

[Gaz]

If you're just talking about switching, it's like what Don said, but I will try to rephrase it. You just have two reverb pots connected in parallel, and a relay switches between the pots' wipers when the channels switch. You just have to double value of the pots to get the same load on the recovery stage (assuming you're just lifting a Fender reverb circuit). Hope that's helpful.

[DonMoose]

Can both channels be used at the same time? If so then perhaps the channel mixing for the wet signal is done prior to the reverb driver, with a pot for each channel.

Hmm - and then a sort of reverb master after the recovery stage, giving you something like the 6G15's Dwell (mixer stage) and Level (recovery vol) controls. Neat!

[tubeswell]

Um... two different reverb loops (one for each channel)?, with the reverb for each channel being recovered at or before the PI?

[matt h]

(deleted)

[tubeswell]

If this were for a scratch build, I'd use a pair of paralleled triodes for the recovery, with split plates--each to its own "reverb" pot.

Yup I also considered the possibility of somehow mixing the two recovered signals after each level control (like into opposite sides of a LTP).

However, each channel still needs to supply a reverb driver with a signal. If the driver was common to both channels, then the dry signal from each channel would appear in the dry signal of the other channel (through the coupling caps feeding the recovery stage). Therefore, as well as increasing the AC load on the dry signal, you would lose the '1 reverb for each channel mojo' methinks. I stand to be argued with in this regard.

[roberto]

Yes, two pots and ldrs is the way Mike managed the two dedicated reverb levels.

[tubeswell]

Well that settles it then.

[M Fowler]

Thanks guys.

[gingertube]

Kevin O'Connors London Power "Standard" does it much as described by Roberto above.

2 Reverb level Pots off the Reverb Recovery Amp. Stage. J-FET shunt switching on the wipers of the 2 pots to short the "un-used" side to 0V.
Passive mix but with alternate inputs being shunted to 0V when channel switching. The J-FET switching is fine as you are only switching a few AC signal volts maximum.

It is really nice to have separate Reverb level controls for each preamp channel (after you have fitted separate tone stacks then this is the next logical improvement).
Cheers,
Ian

[10thTx]

I'd probably try something more like this using a one tube reverb. It could be changed to use a 12AT7 for the reverb driver to make it more Fenderish if one wanted.

Then use an ABY box for switching.

There is a B+ rail drawn on the 2nd page of the SCH file.

It should be noted the SCH is editable if someone wants to change it.

IF you needed the reverb to be set different for the JCM800 vs. AB763, it would be very easy to use a 500ka reverb dwell pot with a resistor to ground that is switched in by a relay.

With respect, 10thtx

[M Fowler]

As we know the AB763 side would have great reverb quality but the JCM or JMP would drive the reverb too hard so Soldano went with individual reverb pot on each channel.

Not understanding how to use the LDR in a reverb circuit though.