EL34 negative voltageHi all, on suppressor's

[BillnShell]

Hi all, I'm going to convert my Plexi clone to cathode bias, and thought I'd use the existing bias supply to provide a negative voltage on the suppressor's. While the supply is presently adjustable between -35vdc and -42vdc, I'm wondering what range is practicle for this application? Also, for those that have tried this, what effect does it have on tone and power?

Thanx!

Bill

[zaphod_phil]

It doesn't have to be anything exact. So use whatever voltage in that range you have there, and it will help extend the life and improve the performance of your EL34s. When running cathode biased, in fact connecting the suppressor grids to ground will achieve exactly the same result. If however you decide to make it switchable, then connect the suppressors to your bias supply.

[RossH]

If you do that -voltage thing to the suppressor without a switch, doesn't it limit your tube usage to pure pentodes? Being that beam powered pentodes are internally connected doesn't that let you not use KT66's, etc?

Ross

[zaphod_phil]

No, that pin isn't connected anywhere on beam tetrode tubes, or physically doesn't even exist.

[BillnShell]

I'd completely forgotten that going to cathode bias would put the suppressor negative to the cathode ( provided I remove the connection on the sockets linking them ). Thanx Phil..

Bill

[RossH]

Not connected, or doesn't exist. Got it. Thanks.

Ross