Marshall JVM Stock and Satriani Variant Negative Feedback Question

[greengriff]

Looking at both variants of the amp there is a cap bypassing the negative feedback resistor. 120p for the stock model and 100p for the Satriani model. This is not something I've seen on any other Marshall. Excuse my ignorance if I'm incorrect but that would seem to allow certain frequencies to bypass the resistor, massively increasing feedback above that threshold. What's its purpose?

[alexradium]

it's called a speed up capacitor,its role is to stabilize the power amp against hi freq peaks especially with difficult signals like square waves,not much required in a guitar amp but for sure in hifi,that shows the designer has studied and wants the product to behave correctly all the time,which is typical of big brands mass producing,they always include filters in input and output to eliminate any inside or outside disturb potentially harmful.

[greengriff]

Thank you very much.

[J M Fahey]

Looking at both variants of the amp there is a cap bypassing the negative feedback resistor. 120p for the stock model and 100p for the Satriani model. This is not something I've seen on any other Marshall. Excuse my ignorance if I'm incorrect but that would seem to allow certain frequencies to bypass the resistor, massively increasing feedback above that threshold. What's its purpose?

SCHEMATICS??????????????????????????

[g1]

SCHEMATICS??????????????????????????

Here's the JVM210. NFB resistor and cap down below PI tube on pg.2

[Delta362]

Here are the schematics for the JVM410H and the JVM410HJS model.

[loudthud]

Do both amps use the same output transformer ? One schematic says D5118, but the other doesn't say.