How hot do you Bias your Amps??

What percent Plate Dissipation do you Bias at??

  • 40%

    Votes: 1 3.2%
  • 45%

    Votes: 0 0.0%
  • 50%

    Votes: 1 3.2%
  • 55%

    Votes: 2 6.5%
  • 60%

    Votes: 8 25.8%
  • 65%

    Votes: 7 22.6%
  • 70%

    Votes: 6 19.4%
  • 75%

    Votes: 1 3.2%
  • 80%

    Votes: 0 0.0%
  • NUKE

    Votes: 5 16.1%

  • Total voters


Well-known member
Inside my Fryettes it states that he recommends 70% Plate Dissipation, but also gives numbers to set it colder..

BTW, how cold do Mesa Amps ship?? I owned a MV, but never checked it and left it up to my Tube Vender to give me the right Power Tubes..
It's been said that they ship their Amps cold. This helps with Warranty I'm sure, but they haven't had a problem gathering a following for their products either. So maybe Bias isn't all that?!?!..

I've experimented briefly and extreme settings aside, it's subtle difference that most drunken townies in the crowd wouldn't be able to tell the difference..

So hit the polls and give it up..


Well-known member
If it's the PCB as in Printed Circuit Board - often these will indicate maximum thresholds, not "optimum operational range". I can't speak for your particular amp and its related printed circuit board, I only know from my experience of working on a lot of amps, upside-down with biasing and the like, 80mA is fkn hot.

As for the comment above re: EL34 - yep - 25mA was the "hotter side" of those tubes back in the 80s; with many cats bringing them down to 20mA each for a more chunky punch.

I ❤️

Wish I would’ve done this so much sooner in my Herbert, unfortunately mine is an older model that doesn’t have external bias points, so it’s much more of a pain to do on the fly unfortunately. To me, running EL34s that hot is the same ridiculousness that people who “bias modded their 5150s to run hotter” and think that sounds better... they don’t, like at all, and are biased cold for a reason. Of course, these aren’t even remotely similar amps, however the same principles apply of course as far as tonal characteristics of a hotter or colder bias. I encourage everyone to Atleast try EL34s in the 40-45 ma range, especially if you have external bias points: it isn’t going to hurt in the least, if anything it’ll be quite the opposite. Especially if you mic up your amp often, the differences will be much more clear under a mic and monitoring in isolation on studio monitors.

"I copied this from a posting on the Diezel section.
I know going lower on my Herbert III does open it up.
Same gain. Saturation . Low end etc."


Well-known member
lol. I embarrassingly have never biased an amp. I have all the shit to do it, but never had the tubes sound bad when i changed them, so been kinda lazy



Well-known member
I warm mine up to 70% since snapping up a Variac. I set them at 120v so they are ‘safe’ any time I need to plug into straight wall voltage. But when at home, I drop my amps ever so slightly to 110v. Bias is probably 65% at 110v?


Well-known member
I cathode bias JJ KT77’s over 30 watts.

I have been accused of being like this punk kid that used to hang out at the Schecter shop named Eddie.


Well-known member
Since most amps generate their gain from the preamp, (high gain amps anyway), I tend to run closer to 60-65%.


Well-known member
I go as cool as I can while not losing tone, using my ears.
I never could understand how anyone can stand biasing at real hot levels as it just chokes the amp so it cannot breathe properly, but I guess it depends on the amplifier and of course, it’s somewhat subjective.


Well-known member
Anymore these days I'm in the 50% to 60% max, I actually find I care for the tone tightness, tone and dynamics in this dissipation range as you get closer to the crossover distortion point, actually Marshalls kind of likes a little crossover distortion in the sine wave.

I found I didn't care for a 70% of dissipation for my taste, some might like it but hot biases just wear tubes faster for not much a tonal return IMHO.

I do have the bias close to 60-65% in my 68 plexi but it's variaced down hard to like 90 ACV's then I bias it like 40-45ma at 352DCV plate voltage, 70% dissipation would be 49ma at a plate voltage of 352DCV. Then from there I set the variac anywhere from70-85 ACV depending on my mood, I have been running the same Sylvania 6ca7's for quite a few years and the tubes just keep on keeping on....

Most everything else I have 50-55% delivers great tone wihout stressing the tubes too much if at all, I don't have alot of tube failures either haven't had any in years except for some bad JJ6ca7 right out of the gate. My tube longevity is greatly increased due to this.
Last edited:

stephen sawall

Well-known member
Depends on the amp. I haven't found a universal setting that fits everything. I tend to like them on the cold side with more dynamics. But some of my amps like the Fryette Sig X and Deliverance 120 I set where recommend because the sound and feel is just better.