Modding my 900! (All tube, with clips)

iron broadsword

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EDIT - See page 2 for post-mod clips.



Ok, I havent done it yet... but this week I'm gonna mod my dual reverb (4100) and see how it turns out.. I'm using tscharma's info, posted here: http://www.marshallforum.com/workbench/40745-jcm-900-4100-mod.html

I recorded a pre-mod reference clip here - http://ghostsauce.net/random/900 test.m4a

The masters are running pretty quiet, at 1 on each channel. You'll hear 3 takes, the first is with the clean channel with the gain cranked, 2nd is with channel B with the gain at noon, and then with the gain cranked on channel B. The EQ's are all at noon throughout, and it is on full power mode.

After that comes 2 clips where I am going for a metal tone that sounds good to me using channel B. I switched guitars to a PRS Torero (emg 81 bridge) and set the amp to Presence5 Bass10 Mid10 Treble2 Gain16. They're both the same except the 2nd one has a little compression and some slight EQ tweaking added in my software shown here. I did that to show this is about as good as I can get it after the fact.

The head is going through a 4x12 with V30's, and using an SM57. For what it's worth, I really do like the tone of the amp, but this mod should clear out the mud by converting the preamp gain to solely tube generated, and fix the weird EQ I keep saying the 900 has. With any luck, should have the other half of this posted sometime this week!
 
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iron broadsword

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Re: Modding my 900!

Looks like some of the final take got cut off.. I'll fix that later today
EDIT: Fixed now
 
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Nmoc strat

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Re: Modding my 900! (with before/after clips)

I also have this Amp, and love it like it is, I can get a great tone with it. Dont know if its worth The hassle Of mod it, but to each his own.

As for The EQ, I guess The best is all at noon, presence included. :shred:
 

iron broadsword

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Re: Modding my 900! (with before/after clips)

Yip, at least with v30's (the presence is at noon in those clips). With T75's I tend to run it with the bass and mids at full, treble off, and presence at 4.5. Sounds pretty much like the 2nd clip that way except with more bottom.. that's the way I run it all the time.
 

V-Type

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Re: Modding my 900! (with before/after clips)

Try a looped eq. I find you can enhance or subtract easier than swapping componets in many case.
Btw I never thought the 900's sounded bad too begin with though.
Nice tones OP.
 

Rokinroller

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Re: Modding my 900! (with before/after clips)

I like that 900DR grind ! I prefer the 4100 to the 2100 MKIII I had. The DR has this certain evil character on its gain channel PLUS a GREAT clean channel which takes OD pedals very well. All around just a more versatile amp which really shows its power and teeth when you start turning it up. No wonder I gots 2 of them ! Oh and now one is running EL34 , and the other stock config 6L6. But we al know these were originally built around EL34's when they first came out. All in all they are a very desirable Marshall to have. I had bought one 4100 Dual Rev 5881 brand new back in the 90's and am now happy to have 2 more.
The fun part of these....easy to mod if you want. My EL34 one has a couple little tricks to it but still retains its basic authentic JCM 900 character , with just a little bit 'mo!
But do try these 4100 DR's with at least a decent EQ in the loop.....just opens up a whole new dimension without using any soldering iron at all :applause:!
 

iron broadsword

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Re: Modding my 900! (with before/after clips)

I've tried EQ's in the loop, but I find I can get what I want out of it without it. What I am aiming for here is more note definition, mostly, and a little less harshness. It should accomplish it well. This is what it should sound like when it's done, courtesy of tschrama:
https://soundcloud.com/tschrama/lasse-dis-reamp-thr-jcm900

With EMG's I can get REALLY close to this sound, but the note definition is not there like in this clip.
 

iron broadsword

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Re: Modding my 900! (with before/after clips)

Fair point. Either way the mud is gone though, and no amount of eq'ing or compression before hitting the amp is going to fix that. That's what I'm going for, and the mod is so simple and reversible I'd be crazy not to try it.
 

Rokinroller

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Re: Modding my 900! (with before/after clips)

All for it ! looking forward to the after mod clips. I hope it does give what your after ...there is a couple things in that mod formula I just may want to try out as well. Good stuff.
 

Ghostman

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Re: Modding my 900! (with before/after clips)

I've tried EQ's in the loop, but I find I can get what I want out of it without it. What I am aiming for here is more note definition, mostly, and a little less harshness. It should accomplish it well. This is what it should sound like when it's done, courtesy of tschrama:
https://soundcloud.com/tschrama/lasse-dis-reamp-thr-jcm900

With EMG's I can get REALLY close to this sound, but the note definition is not there like in this clip.

Teach me oh great one! :shred:

Dude, that was wicked awesome.
 

tschrama

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Re: Modding my 900! (with before/after clips)

This looks like a cool project. Very cool that you made stock clips first. And indeed they do sound allready good, allthough traditional and not very modern sounding.

Are you going to post pics and clips as you progress through the mods?
 

tschrama

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Re: Modding my 900! (with before/after clips)

Careful now....that sound is Re-Amped ! Its not just the amp alone. Yes it does sound killer , but...... there is more going on that than just the amp.

Well, yes and no.

No:
It's just the amp with the mods around the second opamp of the lead channel and the pre-eq. The tracks are reamped at completely realistic signal levels. I made sure I did not pump more gain out of the DI's. I didn't try to make it sound as good as possible. The recording is for my own comparison and evaluation of the mod.

Yes:
What helps is a great backing track, which also included bass. The bass also helps to make it sound heavy. The guitar tracks are very, very tightly played, are down tuned and quad (edit: I think only double, not quad) tracked.

It would actually be great if I would have made such a recording with the stock 4100 as a comparison...but i didn't :facepalm:
 
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iron broadsword

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Re: Modding my 900! (with before/after clips)

That track is what sold me on the mod. It's crystal clear like a great high gain modern amp.. Which tells me the lower gain sounds will sound way better in the same way.

I haven't pulled the chassis yet, so I'll try to put together a modern metal reference clip to go along with the others I did. I generally run the amp like the 2nd clip in the first post, but I do record metal stuff for work frequently with my class 5 of all things... And if the 900 can pull it off this good I'll start lugging it home every week.
 

_ripper_

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Re: Modding my 900! (with before/after clips)

Sorry about jumping in this thread with a (seemingly) irrelevant question, but I wanted to ask tschrama if he's aware of a mod to convert the JMP-1 preamp to pure tube, since supposedly the JMP-1 preamp is the same as the 900DR preamp circuit.

I made a thread recently about JMP-1 mods that I had found online. Its here: http://www.marshallforum.com/workbench/75746-assymetrical-clipping-mod-jmp-1-preamp.html

Maybe tschrama could post his reply in that thread so as to not clutter this one?

Thanks!
Cheers,
_ripper_
 

ampmadscientist

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Re: Modding my 900! (with before/after clips)

Ok, I havent done it yet... but this week I'm gonna mod my dual reverb (4100) and see how it turns out.. I'm using tscharma's info, posted here: http://www.marshallforum.com/workbench/40745-jcm-900-4100-mod.html

I recorded a pre-mod reference clip here - http://ghostsauce.net/random/900%20test.m4a

The masters are running pretty quiet, at 1 on each channel. You'll hear 3 takes, the first is with the clean channel with the gain cranked, 2nd is with channel B with the gain at noon, and then finally with the gain cranked on channel B. The EQ's are all at noon throughout, and it is on full power mode. The head is going through a 4x12 with V30's, and using an SM57.

For what it's worth, I really do like the tone of the amp, but this mod should clear out the mud by converting the preamp gain to solely tube generated, and fix the weird EQ I keep saying the 900 has. With any luck, should have the other half of this posted sometime this week!

As far as gain goes, still pretty weak, compared to what it "could" be...
Low end lacks bottom HUNK, which is typical for a 900.
OK for "rhythm guitar," but a lead guitar player would want quite a bit more.
Good start anyway. Keep going.
 


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