JCM 800 100w 2203 too much bright!!

[grtamp]

Hi , I have a jcm 800 (2203) 100w , It seems to me the tone is too much bright and poor, can you suggest me some tweaks for improved the problem and take more biggest and fat sound?

Thanks
R

[Reeltarded]

What year is it? Are you trying to kill off treble or raise bass? Is the distortion thin or is it just about the EQ response?

Could be as easy as moving the NFB or more involved like changing stage coupling or more.

[xtian]

Removing the bright cap on the volume control is the first and best mod for this amp. I have a 1983 model, and love it.

[xtian]

Another thing: Don't think it's odd to play with the Treble control turned way down. That's just the way to do it!

[john l]

Lots of guys mess with the treble peaker on the input for that. A friend of mine has a 78 that he also thinks is way too bright and he clipped the bright cap off the gain pot and changed the 470k/470pf at the input peaker to an unbypassed 220k and says that put him alot closer to where he wants to go.

My 1980 2204 despite being stock until recently is actually on the dark side of things ...friggin weird. Whenever I read posts like yours it makes me think somethings wrong with mine even though its probably where most people want to make their 2204s sound like. ARRGH

[sergio]

eliminates the bright cap!

[grtamp]

I bought it in the 2006

[Jerry2013]

The later JCM's were brighter if I am not mistaken , than an early Jcm800.
Also, the new cheap crap tubes modern are not optimal; for that amp, and create a lot of brittleness. I run a set of Svetlana Winged C's in mine , they aren't too cheap, they are OOP, still a good tube and much less costly than the ideal set of old Mullards. I assume your amp has EL34's, if not, get them changed to El34's.

Again, clip the bright cap( my bright cap was on the circuitboard. Eassy- snip snip- done..of course, you wanna make sure you clip the right cap of course).

Make no mistake about this; Marshalls are bright amps, thats just the design, and I love it. Mine is a '77 JMP 100 watt, so I think the extra headroom might help with the treble also, not sure. As far as running the treble way down, with good tubes , I run mine at 3-4 and its just perfect.
Invest in a excellent old stock pre-amp tube for V1, it will breathe life into the amp and also get some decent old stock preamp tubes for the other positions, it will also tame the spikey nature of the amp, especially with crummy preamp tubes.

Caveat- Marshall JCM 800 was designed for a 4x12 Cabinet . It was designed ideally for G`12-65's (actually Vice-Versa) which smooth out the treble like a pair of high power greenbacks, or G12H-30's and a closed back cabinet. IMO Greenbacks G12M-25's are not the speaker for the JCM-800, but I could be wrong about that. Also, if you have a hundred watt marshall, run it through a stack. If not, get a half stack, sell the 100 watt and buy a 50 watt.Thats as Father Marshall and God himself intended...so it is written, so it shall be done!

JCM wasnt designed to be mid scooped either..turn up the mids to balance out the sound. Turn up the bass- but it can get bassy fast. I set mine on B-4, M-8, t-6.5. Also, Crank that preamp! Thats why its there, turn the presence down ( I have mine set at just below 7) and buddy, thats loud with the Master Volume at about 7). They were designed to be played loud- if you can't hack that, sell it and get a different amp.

Thats my story and I'm sticking to it. Play it loud, play it proud. Drive it like you stole it. Jcm800's are not the amp for bashful people.

[roknroll]

imho the best remedy is try different speakers and or turn treble down below 3. keep presence low. a previous post recommended g1265👍
this is a great sounding amp just the way it is by just adjusting the stock controls. i cant begin to tell u how many times over the years people have brought in 2203/2204/800 for mods. i test the amp while they are in the shop and get killer tones from the unmodded amp while they stand there saying wtf how did you do that?
also rolling off some treble from your guitar doesnt hurt.
clipping the 470pf changes the character of the amps distortion sound.
an old mod is to remove the 470pf/470k combination and substitute a 68k resistor in its place. actually not bad sounding. or put both the stock and the mod on a spdt switch and try both.
just my opinion

[roberto]

So it seems you have one of the "high voltage" 2203 amps.
Low voltage ones just go muddy when you crank them.

Try to sustitute:
- the 2nd gainstage cathode resistor from 10k to 4k7
- the 22n to 470k//470p to 470k after the 2nd gain stage to 4n7 to 470k to 470k

This will make it sound darker and with a bit more gain.

[bcmatt]

I went through a bunch of mods trying to do the same thing to my 2204. They all seemed to help in subtle ways, as I snipped out resisters and such. I think the most dramatic changes at once were...
Using the ET-65 speaker over other more bright speaker choices...
Swapping out the V1 tube for something a little less gainy. I still used a 12ax7, but going to a tung-sol seemed to bring down the gain and especially the treble a lot. Of course, this was also after \I had removed some of the treble boosting circuits as well.

[Roe]

just turn up the preamp vol/gain to at least 6