High voltage vs current on PP bias.

[jordan86]

I apologize if this has been covered before. My Princeton I just built is my first adjustable, fixed bias amp. Everything I own is el84 cathode biased. The infinite variability of plate voltage dropping as current rises has my brain very curious on the tonal outcomes.

For instance, say a PP 6v6 amp was biased around 9w of plate dissipation one of two ways:

A) 375v PV @ 24ma
OR
B) 450v PV @ 20ma

What would be the major differences in these two scenarios? Would one be louder? Would one be cleaner(more headroom)? I assume the tubes would last longer under option A? I'm additionally curious because my Princeton PT has two HV secondary options, 275v and 325v. I've not started tinkering just yet, but wondering how that 275v tap would sound with the ma pushed higher.

[shooter]

not sure you'd notice much on stage

if it was 300 vs 450, you might
typically the larger the plate volts, the larger the swing of the signal

assuming you don't exceed MAX volts and have zero current your tubes will last forever, assuming you don't exceed MAX current, your tubes will last less,

[66Strat]

What happens to the screen grid at clipping under the two scenarios? Screen grid maximum dissipation is 2 watts. IMO, this is the overlooked elephant standing in the corner.

[PRR]

.....say....A) 375v PV @ 24ma OR B) 450v PV @ 20ma....

Then the no-load voltage must be like 750 Volts. Which is not a likely condition. Particularly since when you segue from a cool silent 24mA bias to a loud 80mA full-roar the B+ would try to sag to ZERO.

> Would one be cleaner(more headroom)?

Idle bias has about no effect on full-roar power.