need HELP: Bias Pot values?

[rexindigo]

im just gathering parts for my JTM50 Clone project and for the first time i m confronted with a bias circuit.
as far as i can see from the different schematics i study, the bias circuit is powered from the high voltage secondary and rectified only one way ( so it gets negative?) and filtered with two caps about 10 mF. am i right that the bias pot is a trim pot?
1.) but now to the questions: what wattage should this pot (50k) have?
2.) is it possible to make the bias adjustable for both powertubes individually ( so i dont have to use matched pairs) maybe just substitute the bias splitter resistors with pots ?

i am refering to the following schematics and layouts:

http://marstran.com/10513%201987.gif

http://www.bnv-gz.de/~ooehmann/schem...87_notated.gif

http://www.el34world.com/Hoffman/images/Plexi50.gif

http://www.ceriatone.com/images/layo...dceriatone.jpg

Thank You for any help!!

[stokes]

Watage rating of the pot is unimportant,there is little or no current in a bias supply.I recommend using a cermet pot for this application,a multi-turn cermet is best if you can find it.I wouldnt advise subbing what the schematic calls bias splitting resistors with pots.They are not actually bias splitting resistors,they give the grids of your power tubes a ground reference.If you want a bias balance set-up,so you can use mismatched power tubes check out some Fender Silver Face schems,they used a bias balance scheme.But be advised many people modify this circuit back to the Blackface true bias adjust circuit.Matched tubes are more readily available today than they were in the '50's and '60's.

[rexindigo]

Thank You very much Stokes, this is very helpful, i will try to find a cement pot for this and forget about the individual tube bias adjustment ( for now).
As i just got a bunch of unmatched el34 tubes i can start with them and then buy a good matched pair when i have the amp up running.

[stokes]

The tubes dont need to be an exact match.If they draw within 5ma's or so they will be fine.Try www.surplussales.com for the trimpots.Go to "Potentiometers-PC mount-Multi-turn Trimpots".These are the ones I use.

[rexindigo]

Hello Stokes,Thats a very good link, because I can see a picture of the trim-pot,(i even have one of these lying in my crap-box)
Thank You again for Your help!