Choked 5e3 screen voltages

[walch277]

Hi all,

I've just built a 5e3 with choke filter. Has 470ohm screen resistors.
Sounds great, Screen and plate dissipation acceptable with 360ohm cathode resistor.
Problem is, my screens are 4V above plates at idle. 334V vs 330V on the plates.
I gather I shouldn't be too worried about screens a couple of volts above plates, but I'm not sure where I stand with this discrepancy.
Should I add some additional series resistance to the screen supply and will this have a significant effect on tone?

For the life of me, I can't figure out how this amp was even not designed to break up. Even in the 50's people must have been turning them up beyond the point of clipping - rightly so.

[Enzo]

Did you simply replace the 5000 ohm resistor with the choke? The choke adds some filtering action, like adding a cap would, but it won't have the voltage dropping effect that a resistor has.


Nah, sorry, in the 1950s, guys were playing clean. We had not gotten into LOUD then. Look at the typical band. Bill Haley and the Comets say, typical hard rocking band of the era. Acoustic bass, his guitar as acoustic, he had an electric guitarist too, but he was not shredding or anything. There were guys starting to think about it, but nothing like what we do today.

This was distortion in the day:
Johnny Burnette - The train kept a-rollin - YouTube

Or one of my faves:
Rumble - Link Wray - 1958 - YouTube

And then the 1960s came along...

[Chuck H]

Once the tubes begin to conduct signal they sort of self regulate and don't over dissipate the screens. BUT... If you're going to be clipping the amp a lot the screens may suffer periods of over dissipation, reducing tube life dramatically. At least this is what I've read from the guys here that have dealt with other tweed amps that have the screens higher than the plates. It occurs to me also that if the screen, instead of the plate, is where the electrons are landing the amp will likely suffer a loss of available output power. So there's nothing to lose by trying 1k's for the screen grids and see if the tone is acceptable and the voltage lower.

[walch277]

Thanks, I've added another 470K in series and I now have screens just below plates. No immediate change in tone apparent.

With reference to the 50's, it just seems strange than an amp that breaks up so soon would have found a place in that era.

[CharlieP]

You can still get clean tones out of it by rolling off the volume or pick attack. Volume doesn't even have to decrease much either. Just got done with a practice session.