Change 6922 to 5670

[galyons]

I have a Seduction Tape amp that is redundant, long ago replaced with an Eros Tape.  I want to put it back in service for phono.  Since I will making circuit changes, I am considering replacing the 6922's with 5670's.  Although many folks consider just changing the base pinouts, would there be benefit in changing the cathode resistor? If so, recommended value?  Any other changes?

Cheers,
Geary

[Paul Birkeland]

The 5670 has about half the transconductance that the 6922 has.  While this allows the 5670 to operate at higher plate voltages than a 6922, it also makes it more noisy, and therefore not a particularly suitable choice of tube for a Seduction, especially considering how inexpensive some 6922's can be!

[galyons]

Thanks PB!  I will leave the 6922's.  I thought that the 5670 might be a bit quieter, based only on the net chatter.  I like the 6922/7308's in phono, so that just makes the repurposing easier!!

Cheers,
Geary

[Paul Birkeland]

You could scratch build a phono stage and use several 5670's in parallel, then you'd get them quieter.  This, of course, would require something a bit more complicated than what the Seduction has for power supplies, but it's certainly possible.