I want to fatten up the tone of my stock 2203.

Dean Swindell

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You could always try altering the cathode values of V1A & V1B to mimic the 1959RR values. Stage 1 is 820R / 330uF which after passing through the gain pot cascades into stage 2 which is 2.7K / .68uF
Nice try, but no. The 800 does away with the big fat cap, it's just a resistor. And that comes second; V1a has the .68 and 2.7 on the cathode and they hammer V1b which has only the 820 resistor. To fatten up the sound of an 800 you should try changing the .68 to maybe a 25uf.
 

Dean Swindell

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I really like the ability of any of my 1959s to deliver a fat, wall shaking tone by jumpering channels and mixing some of channel 2 in.

I"d like to get some of that same thump out of my 2203 which is currently in stock form. It sounds pretty thin but yet it is my go-to amp when I want higher gain.
Boosted with a Tube Screamer set to max clean boost, I've got all the gain I want. But it's too thin for my tastes. Oh, it'd probably sit well in a mix, but that's not a concern for me. This is my sit at home and have fun amp. I don't gig. I don't record. I wouldn't want to immortalize my bad playing in any event!

Sure, I could experiment with a few things and figure out something by trial and error, but I can also ask here and somebody might have a short simple answer for me instead, that gets me to the goal with a minimum of fuss and less time spent modding the amp.

So, if you have any mods you know of that will fatten up the 2203's bottom end while maintaining a reasonably tight response, I'd sure like to hear about it.
That thread got really long. Did you try anything yet? I have a couple really EASY and barely invasive ideas.
 

Matthews Guitars

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I've made notes on all suggestions and I haven't yet had a chance to put the amp on the bench and try them out, because I've had a lot of things to deal with, but I'll try to do it really soon, in the next few days if possible. Since I expect to be hunkered down weathering a small hurricane for the next two days, and likely won't leave the house, maybe this is the time? So long as the power stays on, anyway.
 

john l

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Suggestion:
Bass spec tone stack
0.1uF output couplers, 2200pF on treble peaker
47k/8ohm NFB
6550s biased as 25w tubes
Oh and 200+200uF mains cans (=100uF).
I think you and i must have similar tastes lol. I like 2203s/4 pretty much as they are and only deviate bit on my personal amps.

I too use 100/100s for the mains cans. I used to only do this to 2204s but Ive recently found its awesome on the 100 watters too.

I also love 8.2k the first stage rk. Stays firmly in the 800 camp at that value but gives the amp the tiny goose it needs to avoid the strings feeling sticky

Which treble peaker are you talking about? Ive always considered both the one coming off the low gain input and the one on the board to be treble peaking circuits. I personally love upping the one on the board to 1000pf-2200pf.

I always rewire to the scratchy presence and i always use a push pull so i can switch back and forth between .1uf and .68uf. Theres just so many cool tones that having both brings to the table.
The .68uf has kind of made me abandon resonance and output coupling mods at least on this type of circuit….if im building or modding something to be a gain machine then that stuff can still have its place.
 

myersbw

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I don't think I saw...do you have the JCM800 2203 or the JMP 2203? There are differences and I LOVE the JMP 2203...JCM800 version, not so much. Study the schematics for both. You'll see a 3rd 10K voltage dropping resistor in the JMP 2203 series. The Presence control is different, peek at the power tube bias network (all resistors as related to the tube's setup (i.e. not just "bias voltage")

In either amp, I prefer this...volume control bright cap - replace with 120pF silver mica, (100-150pF is the sweet spot for me in the JMP series) . Tubes - I like an ECC803 (long plate 12ax7) in V1, ElectroHarmonix 12ax7 in V2...not preference in the phase inverter. I also MUCH prefer E34L's. I bias just a hair on the cold side as we're looking at a lot of preamp distortion. The softer you go on the power tube bias, the more punch you preserve when you elevate the volume to the extremes. Every little bit helps.

What do I get? My fave Marshall tone to achieve is 70's Kansas. A JMP2203 well serviced can do that. A few JCM800 2203 versions pale in comparison. The iron used is a big factor, cab & speaker selections, etc. If you do have an 800 series, try converting it completely to JMP 2203 specs...not a lot to change, component-wise.
 

79 2203

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I use LP’s usually straight into my stock 79 2203, usually into a 77 straight cab with the original 55hz/30 watt Blackbacks on top and V30’s on bottom. I generally have the Preamp on 5 and the MV no more than 3 for a medium gain AC/DC crunch.
I never have the bass over 3 because you don’t need much bass for AC/DC and the 2203 tends to get boomy with higher bass settings. However I still find that rig very punchy.
Its probably a little punchier than my stock 71 1987 and definitely bigger sounding. From memory it was as punchy as the 98 Superlead(with PPIMV) I had and definitely sounded bigger, with more room filling tops and bottoms than the Superleads focused midrange(though that could be the PPIMV doing it’s thing)
 

wakjob

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Late to the party...

I never liked totally removing the treble peaking circuits, but I have enjoyed playing around with different values in there.

But a fix resonance control is the simplest way to add fullness without tubbiness.
220-330k resistor bootstrapped over a .0022uF cap on the end of the purple wire going to the 16 ohm tap.

...I really wish PhotoBucket didn't hostage all my mod/repair work I posted over there :mad:
 

neikeel

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I think you and i must have similar tastes lol. I like 2203s/4 pretty much as they are and only deviate bit on my personal amps.

I too use 100/100s for the mains cans. I used to only do this to 2204s but Ive recently found its awesome on the 100 watters too.

I also love 8.2k the first stage rk. Stays firmly in the 800 camp at that value but gives the amp the tiny goose it needs to avoid the strings feeling sticky

Which treble peaker are you talking about? Ive always considered both the one coming off the low gain input and the one on the board to be treble peaking circuits. I personally love upping the one on the board to 1000pf-2200pf.
The treble peaker over the 470k between stages (usually 470pF). Then adjust the 'bright cap to taste (IMO you have to have one) I've found 120-180pF works with this combo.
 

jagrenet

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Late to the party...

I never liked totally removing the treble peaking circuits, but I have enjoyed playing around with different values in there.

But a fix resonance control is the simplest way to add fullness without tubbiness.
220-330k resistor bootstrapped over a .0022uF cap on the end of the purple wire going to the 16 ohm tap.

...I really wish PhotoBucket didn't hostage all my mod/repair work I posted over there :mad:
I use this particular mod on ALL of my Marshalls - (at least the ones that require it) - such a simple mod, delivering remarkable results !! - Definitely a game changer. Breathhes life into an amp for sure.
 


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