Smoothing out a preamp

[gdgross]

I asked this over on AX84, but I thought I'd post it here too, and see if anyone has any ideas:

So the core of my rack are are a marshall JMP-1 preamp into a peavey classic 50/50 poweramp, modified by yours truly to add power scaling a la KOC.

It's very very versatile and generally great tones. However, I think I would like the OD side of the preamp to be just a little bit smoother. There are two OD channels that use the same tube. There's a bunch of solid-state circuitry around the tube that I believe changes the drive levels, etc, but the basic two stage OD stage remains the same. I've uploaded a pic of the relevant part of the preamp:

http://www.geocities.com/gdgross2001/JMP_OD.jpg

Any suggestions for smoothing things out just a bit? I know it's a pretty generic circuit, and there's a load of other solid-state stuff in there that I don't want to mess with. What about that diode bridge at the input? I assume it's there for generating distortion? I already use a 5751 instead of the specified 12ax7. That does help simmer things down a bit. I had also thought of trying the single stage triode feedback thing a la Dumble. Supposedly those amps are very smooth.

Or if you just have general suggestion as to how to smooth a preamp out, I'm all ears.

Thanks!
Geoff

[stokes]

If the 5751 is getting you in the right direction,try going a step further with a 12AY7.

[Matt T.]

If that diode bridge is for clipping then it could be changed but I'm not sure exactly what you would change to smooth things out. You could try the diode/LED setup like in a Marshall Jubilee lead channel (just for ideas). Also notice that in the Jubilee there is a cap in parallel with the whole clipping diode network to shave off some fizzy high end.

Or maybe lift that whole diode bridge and then tweek that gain stage to get your distortion...more like a Marshall 2203. Marshall 2203/2204 amps as well as the Bogner Ecstasy and the Soldano SLO (heck...a BUNCH of amps) get most of their preamp distortion by overdriving that gain stage/cathode follower pair and when done right can sound awesome.