high plate voltage on reverb driver

[pula58]

my first build.
I just measured 460V on the plate of the 12AT7 reverb driver tube. Yipes! Is that too high? What is a reasonable voltage. If I add a 10K resistor I think I can drop 30V or so. Would that be better?

[Roe]

you may need a little more than 10k to drop 30v if I remember correctly. although high, 460v is quite common in blackface amps. the silverface amps run lower voltages though (lower voltages seem to be necessary with the 470 and 680 ohm cathode resistors but not with the 2200/25uf).

if you are adding a 10k power resistor you might want to if add a 10-30uf cap as well.
my amp is running 470v so I'm lowering the voltages little myself. however, I'm unsure about how much I should lower the voltages in the reverb driver and vibrato tube.

i like the preamp tubes around 250v, the phase inverter at 300v (for punch) and the 6l6s at 450v at least. this particular amp runs 7581As at 474v, it sounds very clear and powerful. has lots of punch and definition.

[jjman]

Is the tube conducting? Schematic?

[pula58]

https://tubeamparchive.com/download/file.php?id=16052

The tube is conducting. reverb works fine...but the high voltage made me wonder..

[Roe]

bump

[tubeswell]

FWIW there has been a bit of recent discussion on this on the Hoffman forum:

http://www.el34world.com/Forum/index.php?topic=11126.0

[Roe]

thanks for the nice link. I'm gonna experiment a little with voltage now

[Roe]

the 680 sounds fuller and better to me than the 2200/25uf but you need to lower the voltages a little.

[pula58]

the 680 k sounds fuller and better to me than the 2200/25uf but you need to lower the voltages a little.

by 680 k do you actually mean 680 ohms in the reverb driver shared cathodes?

[Roe]

the 680 k sounds fuller and better to me than the 2200/25uf but you need to lower the voltages a little.

by 680 k do you actually mean 680 ohms in the reverb driver shared cathodes?

yes, sorry about that