Marshall Class 5 JCM800 mods

[tertiumsquid]

Hi all, I'm looking to mod one of my Class 5's to be more "metal" (I don't like using pedals). I've drawn up a schematic so far (with some help from the illustrious Lyle Caldwell over at the MyLesPaul forums here, but as I don't know tube amps well enough, I ask for some more education and assistance.

For what it's worth, I know how to work on a tube amp safely and I have certification in electronics repair (though sadly they don't teach tubes at any of the local universities here). I'm learning what I can from various websites and books ("The Tube Amp Book" and "The Guitar Amp Handbook").

Anyone wanna check over my schematic and see if it needs a little help? I'm not sure about R26 - as soon as I turn down the MV, it'll disappear. Apparently I'll also need negative feedback and a presence control to make this JCM-like, but is that really necessary if I'm looking for more preamp distortion than power amp distortion?

[sepulchre]

Okay, I'm not familiar with the Class 5 models. But here are a couple of places that might get some of the info you're looking for. I'm sure someone here will chime who knows a lot more than I, but I think you will get som benefit from these links. They represent some of the very best sources.

For Marshall mods: http://www.webphix.com/schematic%20heav ... tions.html

For general tube amp guidance:
http://www.valvewizard.co.uk/

http://www.aikenamps.com/index.php/white-papers

[Phil_S]

Just checking here...all the yellow components are the modifications? I'll assume "yes" and that the Class 5 is a PCB amp. Given the overall parts count involved, it might be simpler to remove the board, and replace it with a turret board built to your own design. This will give you the added benefits of being able to restore the amp to original and to use the turret board as something that is more easily modified when you decide you'd rather try this or that. I seems to me that it is impractical to do so much modification to an existing board, PCB or turret. Just my 2 cents. Good luck with it.

[tertiumsquid]

Ooh, more reading! Thanks sepulchre, those look like good links!

And Phil_S, yes the mods are the yellow, and pink is new components where there were none. I'll consider turret board, though it might be easier for me to make mistakes. I'm more comfortable with PCB's, though I suppose there's nothing wrong with learning something new :p

[sepulchre]

+1 to what Phil said. If you want to learn about tube amps building one (or 100) is the way to do it. This forum is another Fine source of reading material too.