- Nov 8, 2021
- Reaction score
You needDoes anyone have a correct schematic for the JMP 2204? Seems to be a bit of conflicting info on that. I plan to eventually update and replace the potentiometers. Does anyone know the proper values-audio/linear taper etc? Would love to find a step by step video/pictures instruction for updating to the cascaded gain update.
the whole Signal from
your high Input goes through this Low-Input
Bournes seem the best current choice for 10% taper pots.
For about the past couple of decades, the track CTS use doesn’t have the wiper move off its CCW end stop until it’s rotated maybe 15% of the available range.
So on a typical Marshall faceplate, that’s 0-2, ie the wiper doesn’t reach the resistive part of the track until after 2.
Not entirely correct they were the first batch in 76.As i told him about the low jack i
forgot that the early 2204s were not
cascading the Inputs.
That change occured 1978 or something,
the 100 watter MVs had the cascading preamps
right from the start.
That’s pretty typical for pots, I suspect that almost all production amps ever used pots with that tolerance spec.Looking at mouser and they all seem to be 20% tolerance.
Of course I have not got the amp in front of me to test but this issue with pots is a weird one. A carbon tracked pot will drift up a little - in the vintage amps I fiddle with most of the best amps have high testing pots (often >20% in the case of the old AB/RS labelled ones. Sure if they have damaged tracks that can’t be cleaned/lubed to be quiet then of course replace but I really doubt that it is the issue here.