tschrama wrote:.. all above post IMHO are worthless, including the French article. That guy is hopelessly lost about what's actually going on in the JMP1.
So congrats! Finaly someone makes some sense on modding the JMP1: 1] Clean channel POT: great suggestion, 2] increasing EQ sesitivity, great suggestion. I am not sure if you fully realized it: the JMP1's secret is that de clipping comes from IC12b (Vmax 5.6Volt). If you change the volatge divider R92-R91, to prevent clipping at IC12B pin15, you will about 19dB of overdrive.
tschrama wrote:I think the designer of the jmp1 made an error in the clean Channel. R84 is 1meg but, to my ears , clearly should be 330k.
I put 470k across r84 ...Much better !
tschrama wrote:The cathodes are not the classical fender 1K5, because of the low V+ (160volt) in the jmp1 versus 260V in a fender*. I think marshall chose 3K for stage1 and 2k7 for stage 2, to keep the bias point, (relatively) similar to the fender bias point; which in fact is assymetrical in both the jmp1 and fender.
devastator wrote:if a proper traduction of the french document is wanted , let me know .
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