split plate resistor

[catalin gramada]

Hallo
I want to start a 5F6 project. Friend of mine gave me original transformers. I have a bunch of good nos 12ax7 to use. Cause I have not any 12ay7 my question regard a substitution for V1 with 12ax7. Do You think if I use split plate resistors to fit the voltage gain in respect with 12ay7 will be a honest compromise , please? I don't expect to sound as same, just to be a resonable solution for circuit.Thanks
Catalin

[Dave H]

It sounds fine to me. The input overload margin will be reduced a little. That's all.

[ThermionicScott]

I'm a little late to reply, but if you build up the front end as normal but leave off the cathode bypass capacitor on V1, you'll roughly halve the gain. Another option to consider...

[pdf64]

The downside of that option is the stage output impedance will increase, to be a lot higher (~10x) than it would have been with the stock arrangement, and the lack of cathode bypass makes the stage more liable to heater hum transfer, just at the point where the highest hum rejection is desirable.
That said, many Marshalls seem to do use no or partial 1st stage bypass without hum being a problem.

[ThermionicScott]

Those are good points, and one outcome of using lower-value plate resistors would be increased even-harmonic distortion, often considered desirable.