Marshall 'presence' control, why not on similar era Fenders?

[Dave H]

But on the Preamp side, the two resistors leading from the divider point of the feedback to the long tail pair cathode: on the deluxe its 22k and 470 and on the Concert its 6800 and 820. It looks like those two resistors affect how feedback is introduced into the long tail pair, is that correct?

Those two resistors are the tail resistor and bias resistor. The larger 22k tail resistor will make the LTP outputs better balanced but it reduces the output swing somewhat which is OK with 6V6s. The Concert has 6L6 which need more output swing from the LTP. I think that's why the tail resistor is 6k8. The LTP outputs won't be as well balanced with a 6k8 tail but they have compensated for that by reducing the left hand side plate resistor to 82k. The tail and bias resistors have very little effect on the negative feedback. The feedback is set by the 27k from the OT and the 4k7 resistor with the presence pot across it.

[mikepukmel]

Those two resistors are the tail resistor and bias resistor. The larger 22k tail resistor will make the LTP outputs better balanced but it reduces the output swing somewhat which is OK with 6V6s. The Concert has 6L6 which need more output swing from the LTP. I think that's why the tail resistor is 6k8. The LTP outputs won't be as well balanced with a 6k8 tail but they have compensated for that by reducing the left hand side plate resistor to 82k. The tail and bias resistors have very little effect on the negative feedback. The feedback is set by the 27k from the OT and the 4k7 resistor with the presence pot across it.

Thanks Dave.

[bitjohn]

Thank you Dave and everybody else in the thread!