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Any tips for modding a Marshall JCM2000 to reduce the harsh tone on the high gain channel? Is it as simple as clipping a bright cap?

Got a schematic of your amp?

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http://pdfelectronics.com

No schematic. I'm going to open it up tonight and have a look. Being one on Marshall's newer amps I didn't know if it would have a bright cap like my 50 watt plexi. We'll see.

Depends on which bright cap and how you use the amp.

I don't know exactly how the 2000 is wired, but on the old 2203/4 (with which it shares some heritage I'm sure), there were several "treble peaking" circuits. One was the bright cap on the volume control, and another was a 500pf cap & 470k resistor between the input & gain, and a third was a 500pf/470k network between v2p2 & ground. I have experimented with switching all 3 in/out on my 2204 build and here's what I've found - purely my experience here.

The bright cap on the vol never made any sense to me. It does keep the amp from sounding muddy at low volumes, but the effect lessens as the volume goes up. At full volume it has virtually no effect at all. I removed it and I have no complaints.

The other two I have bypassed at times, and even had the one on v2p2 on a switch for a while. Both cut some of the brightness from the amp, making it fatter and more JMP/plexi-ish, but it also lost a lot of the signature 2203 sizzle/burn when wound out. I have since hard-wired both of those back in.

Which JCM2000 are you modding? I find the TSL to be really shrill & fizzy and could use some taming. The DSL I like a lot more - has a warmer feel. I've poked around a little online & much harder to find DSL/TSL mods than for the older Marshalls.

Darrin

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SG + Brit tube head = Nirvana

In my opinion this Marshall model is crap. It doesn't really resemble their "older" designs and for someone like myself, who only has experience with point to point, it's better to leave well enough alone. The internal components are cheap. I put some nicer 12AX7's in and added some reissue Mullard EL34's which definitely helped take some of the edge off. Properly biased is sounds just OK.
I recommended to my friend that he sell it and get a 2203/2204. Or better yet, let me build him a Trinity 18.

Heh...yeah, that's the ideal approach! Trinity 18w Plexi is a killer amp.

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SG + Brit tube head = Nirvana

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

ROADSTAR

The JCM 2000 DSL is an awesome amp. Get some good tubes, and check your boards for burning, check the amp for and bias drift and you should be good.

I own one, LOVE IT You got to remember Green is Like a cranked plexi as you increase gain (red) the mids get accentuated more causing the person to feel the sound is "thin" when it is actually the way it is supposed to sound when there is more gain stages present

I put in JJ preamp tubes (v1 high gain low noise) and v2 was a JJ with 100+ gain both triodes on a maximatcher.
I put a JJ ECC803s in the PI and used JJ 6CA7 power tubes it kicks ass

Mine's unmodded, however it was fully reconditioned it kicks ass

To answer your question,

there is a mod called the (C12 cap clip mod)

Google it, It smoothens the EQ from red to green