Quote:
Originally Posted by DragonSarc
I checked the Trim pot switch on the board and theres only 1 trim pot - does that adjust all the tubes? cuz on the Video on the euro tube shows 2 trim pot for the JCM 800 i know its 2 different amps im just making sure. thanks  |
You sure the vid showed two trim pots on a JCM 800? My JCM 2203 has only one and most of the schematics I've seen have shown only one.
With one pot it basically raises/lowers the amount of voltage to the resitor network connected to the grid of the tubes.
This is why using matched tubes are recommended as tubes can vary widley in internal resistance and because the same bias voltage is applied to each, mismatched tubes will show different DC plate currents. Personnaly I like 'em slightly mismatched and you'll rarely get a set that's perfectly matched anyway.