novosibir wrote:GTRroddin wrote:Do tell Larry.......
Shure
For a MV Marshall (2203/2204) as follows:
Use a 1N5231B as for the zener with a 1N4007 in series as mentioned above from the gain pot's wiper to ground. Then throw out the 470K/470p going to the input of the gain pot, snipe off the .001 bright cap, sitting on the gain pot's lugs. Increase the gain of the 2-nd stage by swapping in a 3.9...4.7K cathode resistor and bypass the plate resistor of this stage with a 470p ceramic cap of at least 400V or a 500p Silver Mica.
Although there's a .022 to the gain pot, there's no problem with muddy sound due to the zener's influence! And if you'd like to do some more 'fine shape', then change the voltage divider between the 2-nd and 3-rd stage from 470K/470K to 680K/220...330K, but keep the 470p across the 680K (the upper resistor).
That's all - killer sound, if the slightly solid state rustling doesn't bother you too much
Larry
Hi all.
I'm new here, found this forum looking for jcm800 mods. I signed up after seeing the wealth of knowledge of this community. I hate to dig up an old post but, I need a little help.
I built a 2203 clone and have been tweaking trying to get my ultimate amp. I found the diode mod and decided to try it and it's awesome, it got me what I wanted. Where I need some help or advice is in the fact that I have oscillation with the master up around 11- 12 'O'clock (I like to give the heavy handed cymbal smasher the same treatment he gives the rest of us).
Tweaks done:
Diode combo on preamp pot
V1b cathode res. 4.7k w/ .68uf bypass cap
V1a 220k plate resistor
V2 820 bypassed w/ .68uf cap
Resonance control
Should I the 220k plate resistor, add a cap to one of the plate resistors?
The amp is a little dark I would rather not cut any hi end.
It's 98% there for me.
Thanks,
TJ