Ceriatone Forum

Hey guys now the I got my 2203 setup and running its amazing. I was lookin online and seen someguy who modded is 2203 to have two channels. He turned his low input into a 2nd channel with its own master volume and preamp volume. Ran a cable out of each channel and used an A/B switch to channel swap. Is something like this difficult to do? It would be nice to have 2 channels. If possible it would be awesome to have channel thats clean. But a channel with just a 2nd set of volume knobs would do I can get pretty clean rolling the  guitar knobs back, but I need a little more boost in it.

Kevin

No.  "You can't get there from here."

Whoever did that would have had to totally scrap the 2203/2204 preamp and design one from scratch. 

The JCM800 had a unique (at least at the time) preamp. 

For decades before the JCM800 the only different between the HI and LO inputs on an amp was that the LO input was attenuated to weaken the incoming signal. 

With the JCM, the HI SENS input actually runs the signal through a single gain stage and then straight to the LO SENS input, which then runs the signal through a more traditional preamp design.  For all practical purposes, the HI SENS input is nothing but a boost going into the LO SENS input.   Everything is serial/linear, the signal runs through the amp in a straight line  HI input-->Boost-->LO input-->Preamp-->Poweramp.  To make the HI and LO two separate channels with their own Volume controls would really mean running parallel circuits, at least for a little while (for them to have individual Master Volumes, it would men running separate preamps all the way to the PI)

If you want two unique channels, that's where the 2205/2210 series comes in. 

Here is the 2203 schematic.  Note the HI SENS jack runs to V1A, from there the signal goes out the plate, through the .022 cap and runs straight to the physical, mechanical LO SENS jack.  And that jack is switched, plug a cable in LO and it will disconnect the HI circuit from it. 
(http://www.drtube.com/schematics/marshall/2203u.gif)

Hey Kevin -
Wyatt has demonstrated very clearly what I mentioned to you in a PM.  If you rob one of those inputs to make a clean channel you will loose the gain of the other.   That is why you would need another tube to accommodate a clean channel. Then there are the issues of the shared tone stack and other problems. 
Again, as wyatt says, you would be better off worth a different amp, instead of chopping up the one you just worked so hard on to build.  Try  playing with pedals, pre-amp tubes, and guitar volume roll-off and see if you can reach a happy medium.  Your amp is still very new to you, the two of you have some getting acquainted with to come.   My experience is that it is easier to dirty a clean amp than it is to clean up a dirty one.  But I think it is within reach of finding a compromise with your 100 watt 800.
Good Luck

Ok I didnt know that it was a huge deal, I was misinformed, Im quite happy with this amp :)

Kevin

It's not that difficult! I think it's done with relays. Relay Switching in HI/LOW input and preamp/master volumes.