Seductor input impedance

[xcortes]

Back to my project of using multiple Seductors in series. Question, can the input resistor (hence impedance) of the Seductor be increased? What would be the limit?

Thanks

[Paul Birkeland]

How high do you want to go?  At some point, if you go high enough, some voltage will develop across the grid leak resistor setting the input impedance, and that is to be avoided.  If you can scrounge up a 10M pot, you could roll through 10-20 6AU7's and adjust the grid leak till you see -0.1V across the resistor, then have a look at how consistent and how high those values are.

-PB

[xcortes]

I'm thinking eight in series per channel so the inputs would be in parallel. Ideally I would love the preamp to see 100k but that would mean 1.5 meg which seems like a lot to me?

[Paul Joppa]

1.0 Meg is a common spec for these small signal tubes. The 6AU6 specification does not say, but that should be OK. 67K seems a small price to pay.

[Paul Birkeland]

I'm thinking eight in series per channel so the inputs would be in parallel. Ideally I would love the preamp to see 100k but that would mean 1.5 meg which seems like a lot to me?

It's sort of a lot, but when they are all paralleled together, you have a nice low impedance for that occasional 6AU6 that wants to let some spare electrons through. 

[xcortes]

Perfect!

Thanks