Any guys here still playing a stock 2203

glip22

Well-known member
I have 2 JCM 800's that are modded with an extra tube. Its a great mod that adds 2 tube gain stages when engaged. What is so cool about it, is that with the push pull pot (extra tube), disengaged it is a bone stock JCM 800. Literally bone stock with zero changes to the original circuit. Can anyone guess how this is possible? With the extra stages engaged the amp cleans up better than any mod I have played to date. From clean to crunch to ripping high gain with hardly any change in volume.
 

LP Freak

Well-known member
I have 2 JCM 800's that are modded with an extra tube. Its a great mod that adds 2 tube gain stages when engaged. What is so cool about it, is that with the push pull pot (extra tube), disengaged it is a bone stock JCM 800. Literally bone stock with zero changes to the original circuit. Can anyone guess how this is possible? With the extra stages engaged the amp cleans up better than any mod I have played to date. From clean to crunch to ripping high gain with hardly any change in volume.
Who did the mod?
 

RedPlated

Well-known member
I have 2 JCM 800's that are modded with an extra tube. Its a great mod that adds 2 tube gain stages when engaged. What is so cool about it, is that with the push pull pot (extra tube), disengaged it is a bone stock JCM 800. Literally bone stock with zero changes to the original circuit. Can anyone guess how this is possible? With the extra stages engaged the amp cleans up better than any mod I have played to date. From clean to crunch to ripping high gain with hardly any change in volume.
Very possible. I have one of my mods set up just like this. Pull the second gain control and it disengages the 4th gain stage, totally out of circuit. Push it in and it’s fully engaged. Not that difficult really.
 

ErikT

Well-known member
Sold my modded 2203 cause it was bone crushingly loud. But man what a tone. Still have my '79 2204 that I'm having a headshell made for. Double boosted it slays (and can be played at apartment friendly volumes). Thinking of ordering a Legendary Tones V2 to try. 😁

I know at least one of the dudes from Power Trip uses a boosted 2203, the dude from Bring Me The Horizon too nowadays. Also, this dude Euge Valovirta (check out his YouTube channel).
 

glip22

Well-known member
So all stock JCM800 with an added fourth gain stage? Where does the stage come in to the circuit? When the added gain stage is not engaged, my mods are 100% bone Stock JCM800 circuit. Zero changes to the stock Marshall. My amps add 2 extra gain stages with the added tube.
 

RedPlated

Well-known member
So all stock JCM800 with an added fourth gain stage? Where does the stage come in to the circuit? When the added gain stage is not engaged, my mods are 100% bone Stock JCM800 circuit. Zero changes to the stock Marshall. My amps add 2 extra gain stages with the added tube.
Mine is not all stock but that doesn’t matter. It could be and it would still work. I inserted the extra stage between the factory second and third stages. You just break the connection with a switch and it’s like the extra stage was never there. Just like anything else on a switch.

The amount of stages added doesn’t matter either. If it’s only one extra tube, yours is just taking signal into one grid of the extra tube, coming out of the plate of that side, into the grid of the other side of the extra tube and out of that plate back into the circuit. You’re coming back in with a much more amplified signal to drive the rest of the circuit.

Of course it has cathodes connected on both sides, B+ to the plates etc…but that’s the general idea.
 
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glip22

Well-known member
Who did the mod?
The mod utilizes the horizontal JCM's. I'll be glad to post the circuit pics. I did this one Paul. It's a slightly tweaked copy of an Elan Memran modded Marshall. It brings the added two stages in right before the cathode follower after the existing three gain stages. The tone stack becomes extremely sensitive to adjustments and the amp cleans up better than any other mod I have owned.

It gets a great clean to crunch to ripping high gain with very minimal volume change. You can do it all with this head. I used airplane quality shielded lead. I found a couple of the rare push pull pots same as Elan used. Jose used them also. I could only find an 1/8" shaft in 5K. I drilled a piece of plastic 1/8" shaft from another pot and glued it on. I also swapped a 1 meg terminal disc from another vintage CTS pot that matched it to make the 5K pot the needed 1 meg. The other pot is 500K. Elan uses two 22uf cathode caps bypassed with 1.5K which the caps are too large. I lowered those to 5.6uf which were perfect. The mod is very stable with zero grid noise when you stop playing. If anyone wants to know the exact values I will be happy to share. The only part not in the pic is the .01 cap coming off the other plate going to the gain pot. VXA has a 470K coming off the grid to ground with the bypass caps. Grid resistors are not conventional at 1 meg.
 

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glip22

Well-known member
Mine is not all stock but that doesn’t matter. It could be and it would still work. I inserted the extra stage between the factory second and third stages. You just break the connection with a switch and it’s like the extra stage was never there. Just like anything else on a switch.

The amount of stages added doesn’t matter either. If it’s only one extra tube, yours is just taking signal into one grid of the extra tube, coming out of the plate of that side, into the grid of the other side of the extra tube and out of that plate back into the circuit. You’re coming back in with a much more amplified signal to drive the rest of the circuit.

Of course it has cathodes connected on both sides, B+ to the plates etc…but that’s the general idea.
Exactly. I was surprised at the changes to tmb sensitivity by placing the stages before the follower after the existing three stages. As well as what It allowed as far as the amp cleaning up. On the unreal side actually.
 

hellzington

Active member
I have a 1986 JCM 800 2204 and it's totally bone stock. Never modded. I love that amp.

Without a boost it gets great tones with the preamp gain between 8-10. With a boost, I actually lower the preamp gain to 6-6.5. My favorite boost for it is my Walrus Audio "Ages," but it also sounds good with my Spark and my Plumes.

Although I think there was a use case in the '80s to mod JCM 800s because there weren't a lot of boosts or high output pickups available, these days there are more than enough options to get all of the gain that you need through boosts and pickups. That said, I did order the Hot Mod V2 Evo in early August just out of curiosity. It'll add another gain stage to the amp without modding it.
 

RedPlated

Well-known member
Not all 800’s sound good either. This is probably why some are satisfied with a stock one and some aren’t. Probably 15% of the stock MV Marshalls I’ve had sounded killer 100% stock. The other ones were marginal and needed some minor mods to sound good. Component variances, component changes, hot shield inputs, etc, etc….will all change the outcome of a stock amp.
 

cardinal

Well-known member
I've had a lot of older Marshalls and nearly all of them were modified in some way. When put back to stock, they generally sound the same. But I did recently have a 2204 here that once back to stock, it had a ton of low end (more than I wanted), which was pretty weird.
 

hellzington

Active member
Not all 800’s sound good either. This is probably why some are satisfied with a stock one and some aren’t. Probably 15% of the stock MV Marshalls I’ve had sounded killer 100% stock. The other ones were marginal and needed some minor mods to sound good. Component variances, component changes, hot shield inputs, etc, etc….will all change the outcome of a stock amp.
This feels right. I've heard 800's that are full and rich, and I've heard ones that sound brittle and shrill. A lot of people will talk about the vertical vs horizontal inputs as a cause of this, but honestly there were great vertical 800's made and awful vertical 800's made; just like there were great horizontal 800's made and awful horizontal 800's made.

Funny thing is most players want hand-wired amps with more human "touch" when making the amp; yet, players also want very consistent amps. These two things do not go hand-in-hand. The more human involvement there is in the creation of any amp or guitar, the more variance and imperfection there will be. Another great example of this is the original PAF's. There were no specs, they used whatever parts they had laying around, and every worker wound them differently. High human touch; more variance.

Even in modern gear, this occurs. No two Friedman hand-wired heads sound exactly the same. No two Gibson Custom Shop guitars sound exactly the same. No two sets of hand-wound Fender Custom Shop pickups sound exactly the same.
 
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