2nd channel idea, will this work?

[iknowjohnny]

So i have what could be described as a JCM800 single channel with pre PI master. Heres what i am proposing, please tell me if you see any issues. I want to add another 12ax7 and turn it into a Princeton preamp. The use a DPDT switch to switch the input jack from the current amp's input stage to the new clean preamp and the other side of the switch to decide which one's output goes to the master. So using the same pre PI master and everything after that. Can you see any issues with this? the one thing i'm thinking is the priceton pre won't have near the gain and therefore will be much lower when i switch to it even with it's volume dimed. But thats not really a concern because i wouldn't be using the amp as a channel switcher. I just want a clean preamp to run a clean amp with pedals sort of setup and then have the marshal side for running like i normally do straight into the amp. Like having 2 amps for different purposes.

[John_P_WI]

Switching at the input would make a loud pop.

IMO, it would be better to directly wire to the input grids of each pre without the switch. Leave the 800 pre the same, join the princton pre AFTER the 800 master volume, either with a relay or mix resistors, If using the mix resistors you will have to shunt the signal to ground after the first stage of each preamp which you want turned off to prevent cross talk into the intended preamp channel.

[iknowjohnny]

But other than that it should work fine? When you say no switch at the input, are you assuming i have 2 input jacks? because theres just one with no room for another. As for pops and such it's not problem because i can turn the amp off. But mostly i will turn it on with the switch in whatever position i want and wouldn't be switching it during use. My only issue then is the pots. I really have no room on the front and hate to have them rear. But i'll have tio think on that one. Thanks.

[John_P_WI]

IKJ,

Yes it should work, although it won't sound like the princeton as you won't be pushing the same poweramp, where a lot of the tone comes from IMO. I still think it would be better to join the two channels after the JCM master, before the PI input.

Regarding my comment of not switching at the input, I was referring to hard wiring to both 1st stage tube grids from 1 input jack, non-switching.

hehe, next you will try cascading the princeton pre into the JCM... I know I would...