Marshall Split Channel / Single Channel

[Gibsonman63]

I am converting my Marshall JCM800 4210 to 4010 (50w split channel in a 1 -12" combo to the single channel version)

I have done a half a dozen tweaks and have never been satisfied with the sound of this amp. I am dumping the reverb and effect loop and dropping in a new turret board to make a straight up no frills, grab and go hard rock amp. Now that I am half way throught the wiring, I have discovered something interesting. The 50W split channel amps only have two 50/50uF filter caps. The single channel amps have three. This is true of both the head versions and the combo versions. I think I have figured out a way to cram a 33/33uF cap on the board, which should be close enough.

Is there some logical reason that there was less filtering ont the split channel amps? Is this part of the reason that people prefer the sound of the single channel version?

[pdf64]

From http://bmamps.com/Schematics/marshall/M ... w_4210.pdf and http://bmamps.com/Schematics/marshall/M ... w_4010.pdf
the 4010 looks to have more preamp gain (3 cascaded CC stages rather than 2), so additional B+ decoupling (over the 4210) may be good practice.

[Reeltarded]

Stay with all 50s, you need 5 nodes. Most of the later 80s amps have 4. Split your first stage and rock it, baby!

I like loose 4 holers. I like tight drive monsters. Anything less than 50u on any node makes me frowny. I have tried lowering it in each position and i swear it's better at 50. I may even go 100u mains one day. That's insanity I'd never have thought a couple years ago.

Insanity!

[Gibsonman63]

I was afraid someone was going to convince me to do that. There is not an elegant way put an extra 50/50 can in there without drilling a big hole in the chassis.

[Reeltarded]

No need to add a can. Use a single just for the first node and break it out like an added stage. There is PLENTY of room in there. I have built amps from scratch on two of the 50w heads with switching and reverb turned into single channel freakshows.

It's a great place to start, those amps, because of the space you gain by cutting to the chase. (thump) I really like the iron in those. I think these were 86/87 year models.

[Gibsonman63]

Yep, mine is an '85, so it is in the ballpark and the transformers are really beefy. Since I am further down the B+ string, what is the minimum voltage I can get away with?

[Reeltarded]

Cap wise? I have 450v all across. Sounds close, but it isn't.. it's more than enough. If you have more voltage over on that end something isn't right.

My 4 stagers are F&T 50/50 450v except that first stage is always a teeny little single section. Honestly, I don't need it, but it works a little better.

You can live without it. You multi-can live without it, but you will suffer a lil noise as the original amp did. They are a little under-noded.

har har..

[Gibsonman63]

Much appreciation, brother Miles. You are correct. The original was a noisy little bitch.