How hot do you Bias your Amps??

  • Thread starter Thread starter midnightlaundry
  • Start date Start date

What percent Plate Dissipation do you Bias at??

  • 40%

    Votes: 2 3.4%

  • 45%

    Votes: 0 0.0%

  • 50%

    Votes: 4 6.9%

  • 55%

    Votes: 2 3.4%

  • 60%

    Votes: 18 31.0%

  • 65%

    Votes: 13 22.4%

  • 70%

    Votes: 13 22.4%

  • 75%

    Votes: 1 1.7%

  • 80%

    Votes: 0 0.0%

  • NUKE

    Votes: 5 8.6%
  • Total voters
    58
Do you know who AY's Tech is??
BTW, AY has a shit ton of cash and can afford to blow shit up every night..
Keep that in mind when you Bias for Tone..
 
Devin said:
This is what I've always done. Haven't had anything blow up on me yet :D
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Yep. If you bias too high - you'll know. It won't sound good starting with a 'warbling' sound. I've found.

I mean, I order tubes matched to a spec that I already know is what I want. I may put the meter on to check how well they are matched but I like plug and play. That is the downside of buying used tubes IMO. Unless you have the same plate voltage as what I have, your bias numbers don't mean much to me.


v - Yep. Same @Racerxrated . For the Splawn, I order tubes matched at 32-34 mA. A little hot, but with bias drift it is a perfect starting point.
 
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311splawndude said:
Yep. If you bias too high - you'll know. It won't sound good starting with a 'warbling' sound. I've found.

I mean, I order tubes matched to a spec that I already know is what I want. I may put the meter on to check how well they are matched but I like plug and play. That is the downside of buying used tubes IMO. Unless you have the same plate voltage as what I have, your bias numbers don't mean much to me.
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Yes, it will sound like shit biased too low....or too high.

But, the magic number of 30-40ma usually works with any amp I've ever owned..with 600v PTs down to 400.
 
Racerxrated said:
Yes, it will sound like shit biased too low....or too high.

But, the magic number of 30-40ma usually works with any amp I've ever owned..with 600v PTs down to 400.
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Usually the case, but some amps can be weird about that. The Gjika by default was close to 60ma with my bias meter (I never took out the chassis or messed with it). Might be because it’s class A? Not sure. And my Uber is recommended in the manual to be 22-28ma. Maybe since it’s so high gain. In some amps high 20’s sounded good to me, but yes usually somewhere 30-40 in most amps
 
My THD amps are all biased at 25. My Fryette amps are biased 55. I prefer the sound and dynamics of 25 with almost all amps. But it really comes down to the individual amp and what I am going for. Hotter bias is great if you want that always on thing. But unfortunately you loose dynamics and punch.
How it effects tone if in the normal range of 25 to 40 with most amps very much depends on the amp. Some amps there is very little difference. Other amps night and day difference. It has lot to do with how the transformer is used in the design. If you always play at bedroom volume your probably want a bit hotter.

It is interesting to see the results of the poll. Goes to show there is always a few at that are more extreme settings hot or cold.
 
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Agree with a lot said here... I'm noticing that the typical 100 watt marshall (el34)1959/2203 works and sounds great @ 30-34ma of current draw.. not to exceed 34ma.
 
I bias customer amps at around 60% at 123vac input to the amp. If the all voltage goes down, the bias will be cooler, if it goes up it will go up, either way they should be in the 50-70% range. I do listen to every amp and tweak it up or down if it’s not sounding right, but 60% is my starting point.

I did just bias my Mesa mark Iva after the recap. Amazing how cold the inner set is biased.

Outer pair is 42ma, at 480vdc plate or about 20w. Inner is 17mA for about 8w. In tweed these drop to 13.2w and 5.2W. Been running mine in class a tweed for a long time, explains why the tubes last so long.
 
SQUAREHEAD said:
55-60%
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.
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Old post but I didn't want to start a new one.

I was told years ago that a hotter bias will provide better feel and punch, chewie tones. Not sure why I had a tech tell me that. I'm thinking it is best to bias somewhere in the middle of the range.
Eurotubes tube store guys told me you do want to bias on the hot side but I talked to a tech at Bogner who said to bias cooler or medium for best results. I've read that bussing oo hot can lead to a loss of punch? Not sure, now I just bias based on how it sounds and feels to me and get close to the recommendation of the amp builder. For example I have an amp recommended at 70mV for my EL34s within a range of 60-80. I was doing 75 but decided to go with the recommended 70mV.
Does a hot bias really choke the amp and cause it to be less punchy? I've it said that a hotter bias gives a better feel but now I'm not sure. I used to just assume a colder bias gave an amp a stiffer feel.
I'll have to experiment.
 
Smash said:
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
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Nothing embarrassing about that. I ain't an electronics tech so that shit is for someone with the know how. I just play gutiar and sing into the microphone. Entertaining is what my bias is. If someone here doesn't like that well stick your ohmeter where the sun don't shine!!!
 
70-ish% no more than 18 watt output per EL-34's
 
I just twist the lil adjuster until I think it feels/sounds best to me

I agree it doesn't seem to make much difference, at least in the couple amps I've actually done this on

Edit: didn't realize I had already posted in this thread before lol
 
PSGuitar said:
Old post but I didn't want to start a new one.

I was told years ago that a hotter bias will provide better feel and punch, chewie tones. Not sure why I had a tech tell me that. I'm thinking it is best to bias somewhere in the middle of the range.
Eurotubes tube store guys told me you do want to bias on the hot side but I talked to a tech at Bogner who said to bias cooler or medium for best results. I've read that bussing oo hot can lead to a loss of punch? Not sure, now I just bias based on how it sounds and feels to me and get close to the recommendation of the amp builder. For example I have an amp recommended at 70mV for my EL34s within a range of 60-80. I was doing 75 but decided to go with the recommended 70mV.
Does a hot bias really choke the amp and cause it to be less punchy? I've it said that a hotter bias gives a better feel but now I'm not sure. I used to just assume a colder bias gave an amp a stiffer feel.
I'll have to experiment.
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Think of bias as just another gain control. Depending on the amp, you can literally adjust the bias pot as you play to hear what it does. Hotter bias = more gain. More sizzle. More distortion. But less articulate. Less punch. Looser. And lower bias = lower gain, less distortion, tighter.

It's a balance. You gotta find the right setting that gives you the sound/feel you like. But there are constraints you should watch out for.

You don't want to go so cold that you get crossover distortion.
You don't want to go so hot that you get red plating.

Anywhere within that window is fine and will just depend on what sounds/feels good to you.
 
Techdeth said:
I saw angus tech say this
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Well the guitar tech said that and embellished the story to make it sound good on video.
The amp tech doing the actually work was voodoo Trace Davis who is an admitted scammer and don't know his ass from a hole in the ground.
Thermionic valve amps are very predictable and all tube amps play by the same parameters.
Go against that and the results are predictable, catastrophic & preventable.
 
I'll probably give the more tech-y crowd conniptions by saying this, and I'll admit 5 years ago I would've hated this too, but
I just stick a matched set of tubes in and I don't touch it again until a tube pops or something is obviously wrong.

I used to meticulously measure each bias, and I also tried the "bias to tone" thing where I'd play, tweak, play, tweak, etc and it's all such a chore.

I've yet to have any problems just sticking any set of tubes in a given amp, and I have a lot of amps. The difference between amp circuits is far far more than any little bias tweak would be, but if I only had one or two amps I'd probably be a lot more concerned with squeezing the very best out of it. I barely have time to play at all lately so when I do, I want to fuss less and play more. Same reason why I stopped putting together project guitars.
 
How big of a difference it makes seems to depend on the amp but I usually prefer it pretty low. I like the bite, punch, tightness, aggressiveness of a cold bias. Too hot and it just feels mushy to me, seems to lose highs and lows.
 
Really depends on the amp. Since most amps rely on preamp gain and not so much power amp, I tend to go 60-ish. 70% doesn't sound so good in most high gainers I've had. They tend to mush out.
 
shar-vell Dan said:
Well the guitar tech said that and embellished the story to make it sound good on video.
The amp tech doing the actually work was voodoo Trace Davis who is an admitted scammer and don't know his ass from a hole in the ground.
Thermionic valve amps are very predictable and all tube amps play by the same parameters.
Go against that and the results are predictable, catastrophic & preventable.
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I just went by his words .thought he good . I didn’t know
 
stephen sawall said:
My THD amps are all biased at 25. My Fryette amps are biased 55. I prefer the sound and dynamics of 25 with almost all amps. But it really comes down to the individual amp and what I am going for. Hotter bias is great if you want that always on thing. But unfortunately you loose dynamics and punch.
How it effects tone if in the normal range of 25 to 40 with most amps very much depends on the amp. Some amps there is very little difference. Other amps night and day difference. It has lot to do with how the transformer is used in the design. If you always play at bedroom volume your probably want a bit hotter.

It is interesting to see the results of the poll. Goes to show there is always a few at that are more extreme settings hot or cold.
Click to expand...
Andy has been into that for quite a while. In the 90’s, when I was using him as an amp tech, he would state his preference for around 25mA and I can’t disagree. One time with a JMP 2203, I experimented with the limits of bias with how it actually sounds and with the B+ on that particular head (over 450 but I don’t remember exactly), I didn’t hear a major difference between 18mA and 38mA or so. So 25mA seemed very reasonable with enough room for low stage voltage at a gig but also in normal voltages, giving great tube life.

With how modern tubes are now I would definitely err on colder. Shit, my Stiletto set to Tube Rec, spongy and on a dirty setting gave me readings of 13mA. Set it to clean, Diode and bold it would be at nearly 30mA. I was bored one time and got the adjustable bias mod put in and literally have not taken one reading since I got it done and that was probably 7-8 years ago…lol
I’ve gotten so lazy about amps in the last 10 years, I figured he set it after the mod to a good setting and I won’t worry about it as long as it sounds normal.
Got a ‘75 Marshall 5 years ago or so and have never taken a reading once. It sounded good when I bought it and I figured why worry about it. If I smell something bad, I’ll worry about it. Sheer laziness. ☺️
 
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