Sagging JCM800 pre-amp or blocking distortion problems

8/5/2005 9:24 AM

Doug

Sagging JCM800 pre-amp or blocking distortion problems I've modified a 1983 jcm800 2205 boost channel to 2203/2204 values, minus the cathode follower, I used this tube as the last gain stage (820 ohm cathode) then I tapped the eq in on the plate side. The amp sounds great but doesn't recover quickly. My supply voltage above the plates is only 305v, there are 5 tubes pulling off this supply. The voltage at the plate on V2b is 192v, is this enough? Should I lower the filter cap resistors? if so, how low, what's a good supply voltage? Do both resistors need to match or can I only lower the second resistor to raise the pre-amp tube volts? Would a resistor between the plate and the eq help the tube hold voltage and recover quicker (does that even make sense)?     Here's an original schematic link which I have changed considerably   http://www.drtube.com/schematics/marshall/4210.gif