Jose Marshall

[Valvehead]

Anyone interested in re-drawing the Jose Marshall 2203 schematic thats floating around ?


Id like to try it without the loop , all the switching , and just 1 pre and one master

Is the loop part of the gain/tone/sound of this circuit ?

[J M Fahey]

Please link to it (or post it) so we are all talking about the same.

[Valvehead]

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here :

[Hardtailed]

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here :

I won't spend the time to redraw it unless you pay me

Interesting... so basically instead of cascading the two channel to get more gain, he added an extra cold-biased gain stage in front of each channel, meaning if you jumper you get two parallel cascaded stages. Sounds interesting... Almost makes me want to build one just to try!

Seems there is a switch to go right to the 2nd stages to get the original sound, though I'm not sure the schematic is correct, seems it would ground the output of the first stages when you set to "modded" mode, doesn't make sense (would basically mute the amp). Maybe I just looked too quickly.

The loop is just an "interrupt" before the 2nd gain stages, you can just remove the jacks and hardwire the thing. This is an odd location for a loop...

I don't think you can do that with just one gain. You could always hardwire the gain between the first and second gain stages to set level (voltage divider like in a JCM800), but having the two independant gain for the inputs allows you to balance between the bright and normal channels. That's where the magic lies.

Also, if you hardwire the 2nd gains, you can't use the non-modded mode (you'd have no gain control). The JCM800 has a clever way of bypassing the first stage and still getting gain control, you can look into that if you want, it involves having extra input jacks (the "lo" jack)

Another trick is to have dual-ganged pots to control the first and 2nd stages per channel. That's what I'm doing on my JCM800 clone (which has "Plexi" mode, sorta). Gives a better range of usable gain settings imho.

As for the 2 MVs, it would be easy to omit one and the related switch.
To be brutally honest, if you can't figure out how to do this one, perhaps you shouldn't be building an amp...
Just rip this part of the circuit right off a dead stock Marshall if you need help.

[Hardtailed]

Is the loop part of the gain/tone/sound of this circuit ?

Just to specifically answer this one, it's just an interrupt, it's like a hardwire until you plug something into it. In all logic, it has zero influence on the sound.

It's also pretty useless cause you'll still get distortion after your loop.
Best place to put a loop is after the tone-stack

[Valvehead]

As for the 2 MVs, it would be easy to omit one and the related switch.
To be brutally honest, if you can't figure out how to do this one, perhaps you shouldn't be building an amp...
Just rip this part of the circuit right off a dead stock Marshall if you need help.

thanks for looking but I dont appreciate the last comment . Ive built 4 tube amps with success. I just thought that scem was a cluster - F##k

[Hardtailed]

thanks for looking but I dont appreciate the last comment . Ive built 4 tube amps with success. I just thought that scem was a cluster - F##k

You never know who you're talking to here
Hence the "IF you can't figure it out"

[Joey Voltage]

Keep in mind thats a scheme of only one Jose MV. The circuits were different from amp to amp, and most of them didn't include the diode clipper, and if they did, they had varying clipping thresholds from amp to amp

[Hardtailed]

Keep in mind thats a scheme of only one Jose MV. The circuits were different from amp to amp, and most of them didn't include the diode clipper, and if they did, they had varying clipping thresholds from amp to amp

Oh, so that's really a bridge rectifier we see between the two inputs? Wasn't clear to me.
Never seen anything like this! Wonder how that sounds.

[Joey Voltage]

Oh, so that's really a bridge rectifier we see between the two inputs? Wasn't clear to me.
Never seen anything like this! Wonder how that sounds.

Nope, across the MV in that scheme. it's supposed to be a zener clamp, but it looks weird the way they drew it.

[Hardtailed]

Nope, across the MV in that scheme. it's supposed to be a zener clamp, but it looks weird the way they drew it.

Oh, that unidentified part. Weird.

But still, that does look like a bridge rectifier between the two inputs.

Lots of unusual stuff there! The challenge would be to figure out what really adds to the sound, and what doesn't.

[Joey Voltage]

Oh, that unidentified part. Weird.

But still, that does look like a bridge rectifier between the two inputs.

Lots of unusual stuff there! The challenge would be to figure out what really adds to the sound, and what doesn't.

Nope, Thats just a DPDT switch, most likely the switching element on a push pull pot. there is nothing very unusual in that circuit at all, and the clipper circuit was most likely borrowed from second generation stompboxes like the MXr dist +, or the DOD 250. The 5V zener clamp lops off both halves of the wave in that circuit, and is responsible for a lot of distortion generation. most people who have tried this circuit hate it, and most of the Jose Mods don't have it.