Jcm 2210 mod help

[hotguit]

Hi
i want to add a tube gain stage to my 2210 (86') but i do not want drilling the chassis.
Can i use the last (common) gain stage?
can i use it as an extra gain stage for boost channel only? I would link normal channel to P.I. directely, like in 2203/2204 amps
thank you
hot

[soundguruman]

I think if you change R2 to 1500 ohm
and C2 to 10uF (+ facing the cathode of V1A)
you will be getting more of what you are looking for.
I think you really don't need another stage, just tweak what's already there...

[hotguit]

Hi
Yes, i know that but i want first separate channels (normal and boost completely separated for better clean tones) and then eliminate diodes.
decreasing cathode res in V1A and bypassing it with a cap i think that noise will encrease a lot; what do you think?
Is not better add a gain stage using the last common triode or using a triode from (never used) reverb tube?
thank you
hot

[soundguruman]

No matter what method is used to increase gain, it will also increase noise, and the likelihood of oscillations, ringing, etc...
The layout of the parts and wires can make quite a difference
Basically, all higher gain amps use some kind of suppression to decrease the noise and ringing...
The first two stages are the source of most noise that is amplified by all stages following.
I use plate to grid capacitor, usually on V1A gain stage, which is a method used by Marshall and Fender...(7 pf 1000V, or 2X 15pf 500V in series)
others use plate to cathode capacitor, grid to cathode cap, cap across the plate resistor, cap from control grid to ground...
So if you increase the input sensitivity by any method, you also have to get suppression of the noise worked out also.
There are lots of amp mods with more gain, but to get gain without a lot of noise is more of an effort, that's for sure!
You are not only increasing HISSSSSSS noise, but also amplifying the 60 CPS noise from the filaments, don't forget. This has pushed some preamps to DC heaters instead of AC.
Much More noise just makes it UN-useable.

[hotguit]

even if i add the extra gain stage between the two last triodes? (just before V3a)?
thank you
hot

[Jazz P Bass]

My opinion: you are going to have one heck of a time placing components & rerouting the reverb tube to be used as a gain stage.

Plus, there is the fact that it will be a gain for both channels.

What exactly are you trying to accomplish?

[J M Fahey]

even if i add the extra gain stage between the two last triodes? (just before V3a)?
thank you
hot

Yes.
What matters most is end to end total gain.
The front end will still be very sensitive to hum/RF/buzz/etc. pickup, if later gain is high.

[olddawg]

Seriously ... Have you tried a few boost pedals and maybe a compressor? I have always had better results with an off the shelf pedal boost for gain rather than trying to modify an already excellent amplifier. But that's just me. On the front end a boost is a boost.

[hotguit]

My opinion: you are going to have one heck of a time placing components & rerouting the reverb tube to be used as a gain stage.

Plus, there is the fact that it will be a gain for both channels.

What exactly are you trying to accomplish?

1) separate channels
2) remove diodes
3) free clean channel from MV
4) add an extra gain stage for boost channel
5) bypass rev (???)
hot