Overdrive vs plate voltage

[bluefoxicy]

Hey, the anode voltage on my EL34 is set to the same 300+V B+ as the EL84 I replaced. It should run around 250V (that B+ rail goes 341V into the OT).

What effect does this have on the tube? I can't make it overdrive and it's LOUD, do I need to lower the anode voltage to make faster overdrive (less available power, signal degrades when drawing more power)? Alternately, could I just raise the grid leak resistor to avoid discarding so much signal? I don't want to raise the bias because eventually it will kill my PT... 70mA across there as is probably (25W bias).

I do need to measure the actual tube characteristics and calculate the proper bias. Once I fix that, I'd still like to know what the plate voltage does to overdrive, etc.

[cbarrow7625]

In a tube "overdrive" is relative to both plate and/or bias voltage (depending on the bias setting). A few questions:

1.) Is it fixed or cathode biased?
2.) What is the bias voltage?
3.) What is the maximum drive voltage avaialble at the grids of the power tubes?
4.) What is the maximum AC voltage showing up at the plates?

It could be that you just don't have enough drive voltage to push the EL34's into overdrive. The EL84's would have had a much lower bias voltage than the EL34's (correct?). Is there attenuation upstream of the PI (or in the PI) that you could remove to increase the drive level to the power tubes?