Full Plexi and Full JCM800 preamp switchable

[pjd3]

Hey there,

I'd be real curious to know what problems could come up with having both an entire full plexi preamp board as well as an entire full JCM800 preamp board that was panel switchable (mechanical switch). I realize that this would entail installing 2 more 12ax7's, tone stack pots and components, and possibly
(or certainly) an added branch of voltage divider resistors and Electolytics that may or would be needed for presenting the proper plate voltages and filtering for the different 12ax7 preamp stages, which I'm totally willing to do should this be feasible.

Is this something thats possible?

My knee jerk concerns are:
1. Can proper preamp plate voltages and filtering happen for both channels without detrimental interaction and compromise?
2. Can the outputs of these two preamp boards be toggled right before the Phase inverter without huge pops or arcing?

I realize that many have gone the route of adding in series stages and cold clippers to create a high gain sound and I'll go that route if I have to. It just seems so, so much better to have 2 comprehensive independent and important Marshall sounds, each with thier own EQ and volume pot gain/master volume adjustments. I can't imaging that the EQ and volume settings that are optimal for one channel could possibly be right for the other channel for the majority of times. I am not concerned whatsoever about the added cost, work or real estate in the chassis. There is plenty of space in that Bogner chassis. My only concern is if there are electrical issues that can't be properly addressed doing this as I've proposed.

So whats ya think? Can I have what I believe is the optimum flexible switchable pre Marshall amp or am I dreaming?
(Note: this is what has begun as Sluckeys 6V6 Plexi, the plexi board itself is all done according to Sluckeys layout)

Thank you all,
PJD3

[bmx]

I look at the jcm800 as a cascaded plexi. So, I just put a relay in there and have it switch between 2 stage for "Plexi" sounds and 3 stage for jcm800 sounds. It does work well enough for me. I do end up going with a higher B+, but it is only 1/2 12ax7. Others looking for a more legit plexi tone may find fault with my strategy (I just do the bright channel), so that would be interesting to me as well.

[Roe]

Hey there,

I'd be real curious to know what problems could come up with having both an entire full plexi preamp board as well as an entire full JCM800 preamp board that was panel switchable (mechanical switch). I realize that this would entail installing 2 more 12ax7's, tone stack pots and components, and possibly
(or certainly) an added branch of voltage divider resistors and Electolytics that may or would be needed for presenting the proper plate voltages and filtering for the different 12ax7 preamp stages, which I'm totally willing to do should this be feasible.

Is this something thats possible?

My knee jerk concerns are:
1. Can proper preamp plate voltages and filtering happen for both channels without detrimental interaction and compromise?
2. Can the outputs of these two preamp boards be toggled right before the Phase inverter without huge pops or arcing?

I realize that many have gone the route of adding in series stages and cold clippers to create a high gain sound and I'll go that route if I have to. It just seems so, so much better to have 2 comprehensive independent and important Marshall sounds, each with thier own EQ and volume pot gain/master volume adjustments. I can't imaging that the EQ and volume settings that are optimal for one channel could possibly be right for the other channel for the majority of times. I am not concerned whatsoever about the added cost, work or real estate in the chassis. There is plenty of space in that Bogner chassis. My only concern is if there are electrical issues that can't be properly addressed doing this as I've proposed.

So whats ya think? Can I have what I believe is the optimum flexible switchable pre Marshall amp or am I dreaming?
(Note: this is what has begun as Sluckeys 6V6 Plexi, the plexi board itself is all done according to Sluckeys layout)

Thank you all,
PJD3

1, yes, most 1959s are virtually identical to 2203s here - kein problem!
2 yes, but this is totally unnecessary - just switch in the cold 10k cathode stage - look at the SDM layout