800 filter cap question

[Ivabiggun]

Hi George and fellow tone nuts. I was wondering why you decided to use 50/50uf caps instead of the 100uf/350V ones used on the original. Was it to keep costs down? Sozo has their new Blue Royal caps and I wanted to see if anyone had used them or if just using the 100uf's, any brand, would make a difference in the sound. I know what a stickler you are for authenticity and the originals used 100uf's in series.

Secondly, please correct me if I am wrong here, but I can only see one difference between the JTM's and the JMP circuits. That being on the JMP circuit there is a 100fp cap across the cathode/plate terminals on V1a and it is not there on the JMP circuit. I think I said that right. An earlier post stated that the JMP amps had a smoother distortion as opposed to a buzz saw sound from the later ones. My apologies if I did not get that quite right.

Thanks for the help as always

Yankees kick but.
Iva

[demonufo]

Um, I've never ever seen 100uf/350V caps in any master volume marshall, be it JMP, or JCM800 era.

[Structo]

The 100pf cap is known as a snubber cap and is used to smooth the overdrive a bit.

[demonufo]

Actually, it's there to stop oscillations, and has very little audible effect at all (if any).
You'll find that quite a few JCM800 amps didn't have this cap fitted. Sometimes it's needed to calm things down a little, other times not. With good lead dress and good shielding it shouldn't be necessary.
When using shielded cable on V1, it definitely is not necessary IMO.