Looking for 2204 tube effects loop schematic.

[ncusack]

Hey everyone,

I have a request to turn a Musicman HD 212 130W into a marshall jcm 2204 with a series tube effects loop that will work with +4dB rack effects. This kind of design work isn't in my skill level yet so im hoping someone would lend a hand. Also if anyone happens to have a bit more experience with the musicman amp could you let me know if this kind of thing could even be done. We want to put this into a head so ill be sourcing parts and everything for a scratch build with this one all but the transformers for the most part assuming they will hand the circuit.

Any kind of a starting point would be welcome here.

Cheers,

Neill

[phsyconoodler]

the Musicman layout and transformers are not really compatible for a 2203 build.The PT puts out 700+ volts and there is no way to tame it for a 2203.The layout has a solid state preamp and a tube output and the arrangement is odd and may make you crazy trying to mate a 2204 circuit into the chassis.
  He would be far better off getting a kit from Ceriatone or Triode Electronics.

[ncusack]

Yeah I figured the PT was out of the range for a build like that. Would the output transformer be of any use in a similar build? I don't have any of the musicman specs so im not sure what im working with other than a solid state pre into 4 x 6AC7's

[phsyconoodler]

You probably could use the OT but don't use the ultra-linear taps on the screens.
  I don't know.I did build a super reverb into a musicman chassis myself once but it was a bit of a pain in the ass.It was lots of work and I ended up punting the musicman tube socket location and putting them over by the PT.I used a metal plate over the hole where the power tubes were and used it to mount the preamp sockets.
  Tons of layout issues.Not recommended to any but the most cash-strapped individuals.Hey! That sounds like me!

[ncusack]

Yeah this would be a one off build from scratch so id make the chassis and everything so layout wouldn't be an issue. The guy that gave me the amp is a good friend and pretty much just said have at it but id like these features if possible. Basically im in R&D zone right now so hopefully there are a few more people here willing to lend a hand.

[phsyconoodler]

Well that's much easier then.An effects loop is easy compared to building the amp.Easy to do even if the amp is already built.
  There will be lots of room in that chassis if you make it as large as the Musicman is.
Dump the speakers though,they will suck bad with a 2203.You need a pair of Celestions or Eminence Redcoats.

[tubenit]

Did you look in the ARCHIVES at all the schematics of effects loops that were posted there?

http://www.el34world.com/Forum/index.php?topic=10208.0


And the ARCHIVES thread references another effects loop thread with even more schematics.

http://www.el34world.com/Forum/index.php?topic=4274.0

Maybe one of those will work for you?

With respect, Tubenit

[simonallaway]

If you're prepared to do a scratch build on the chassis and components, and perhaps dump the speakers, then you're gutting the MM just for its transformers which may not be compatible after all.

I would leave the MM alone and just build a 2204 in combo form. Besides, Mark Knopfler didn't do too badly with an HD 212 130 back in the 80's ;)