Marshall SLX 2100 Low gain input mod help!

[Atomicpunk86]

  I'm working on a 94 Marshall JCM 900 2100 SL-X. Great amp. I've done several mods to it all ready. I've changed a few component values over in the preamp for more of a 2203 flavor as well as adjustable negative feedback and depth controls.
   I'm currently working on adding either another input Jack or toggle switch that would work the same as the low gain input on a 2203. Comparing schematics it's looks like I need to come in after the 22n cap at C3. I've tried this in a few different places with a toggle and an input Jack and while I've gotten it to work the tone is very muffled. Almost like a guitar with the tone knob set to zero. What's strange is if I add my old blue MXR 10 band in between the input and guitar it sounds as it should. Crystal clear great tone and obviously minus V1. I can't figure it out. I've wired it up a few different ways and have even sought help from some friends. Any advice would be appreciated. I'll include an improved SLX schematic below for reference. And also a drawing of how I wired up the toggle at one time.
Thanks in advance!!

[Atomicpunk86]

2203 schematic....

[hesamadman]

I'm sorry if I'm not understanding what you're doing but what I am gathering is you would like a low gain setting like that which is in a 2204/2203 by bypassing the first gain stage (first half of the first triode). I don't believe the drawing of the DPDT will work like you want. I believe that if using a toggle switch to achieve this, you will have to redirect the signal around the input of the first gain stage as well as grounding out the input of the first gain stage. If you want to use a toggle switch rathe than two separate jacks, my guess is you would need to use a DPDT. It could be configured in a way that switching down, the signal passes through the circuit as normal (high gain setting). Flipping the switch up, you can redirect the signal past the first input as well as grounding out the first. This is just my assumption. I'm sure someone else with more knowledge will be more helpful. I'm also not sure of what kind of popping noise you would suspect when switching this way.

[hesamadman]

If you are wanting to do what I think you want to do, you could try this method. Now I have not done this before. I know the input of the un-used stage should be grounded out. I DO NOT know if the CC on the plate needs to be grounded out. It is done so on the 2204 but I do not know if it HAS to be done to work properly. If it DOES have to be done, you could always use a 3PDT toggle to achieve grounding out that. I could not find a clear schematic of the jcm900 you want to do, but It would be similar at least to the 2204. Hope this helps a little anyway. And hopefully someone will either confirm this will work or wont work. Good luck.

[Atomicpunk86]

Thanks for the response and suggestion. That's exactly what I'm trying to achieve. Basically bypassing a stage or two with a second input or toggle. A toggle would be ideal since I alreay have a hole drilled in the front of the amp for one but I'm not opposed to using a second input and using that hole for a toggle with a different function. I'll give your drawing a try today.
It does seem like something's not working right the way it's acting. When Ive had it wired up the couple times I've tried it it will work fine with my eq pedal between the guitar and amp. Even with the pedal clicked off it works fine. But as soon as you remove the pedal and go straight in guitar to input it gets the unusable muffled tone.

[hesamadman]

Well there would be a loss since you're bypassing a gain stage but not in a certain frequency. I mean it shouldn't just kill all of a certain frequency.