Marshall MA100H Mods

[Ericur]

I would put a 470pf capacitor in parallell with R7, I im going to redraw the schematic with my mods.

 

[Jon Snell]

This is how Marshall wire it;

 

[Ericur]

Yes but no, that is the optional bright cap, witch on some models/years are omitted, im thinking of the 470pf treble peaker capacitor.

 

[Ericur]

This is how Marshall wire it;

This is closer to a 2203/2204, and in my opinion, that 1 nf cap it WAAAAY to much treble, and you will find allot of forum threads on how to remove this 1nf cap.

 

[shawn w]

Thanks again for the info @Ericur !
shawn

 

[Ericur]

No worries! please report back if you decide to do some mods.

 

[Ronquest]

If you want an 800 sound, study the schematic a bit and turn the entire preamp into an 800. I picked up a MA50 a few months ago and after playing it for 10 min, I had to sell or mod it. I gave up the clean channel, but I have other amps for that. You could still retain both channels but at the time I just wanted the stock sound to go away. The reverb and loop are still in place and could easily be bypassed, but I like delay and verb in the room. Amp is so much better after the mod.

 

[shawn w]

No worries! please report back if you decide to do some mods.

Hi! It's been a minute, but I finally got around to doing the mods on that MA50. When I opened it up, to my surprise, it looks like someone has beat me to it! I've loaded to some photos if you'd care to take a look and see if you know what they were trying to accomplish? Here's what I've seen so far -
C8 removed
R162 and R13 removed
Cap across one leg of C3 and LK38
Cap across one leg of C90 and R24
The other cap in the pic is across R7 that you recommend.
I've installed all the recommended mods. It doesn't appear that any other solder joints have been touched. The changes made previously can be replaced, but I'm still curious.
Whats your thoughts?

Ma50 -1

Shawn

 

[Tatzmann]

So the amp sounded grungy with the mods already installed that you were going to install to make it sound less grungy. Thats funny.

I think a guy above suggested already what has to be done to this thing. Take all the crap pcb's out and throw in a 2203 circuit.

 

[shawn w]

So the amp sounded grungy with the mods already installed that you were going to install to make it sound less grungy. Thats funny.

I think a guy above suggested already what has to be done to this thing. Take all the crap pcb's out and throw in a 2203 circuit.

I don't recall ever saying it sounded "grungy" or that it sounded like anything at all? I do this because I enjoy it and want to learn.
Shawn

 

[Tatzmann]

Very well. But you can learn more by putting a new, more simple and much better sounding board in. Less frustrating, less finnicky, better sounding outcome.

The MA's are destined for this because they have the OV sockets already chassismounted.

But if you have fun doing it, alright, sharpens the soldering skills.