fine tuning bias

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FALKEN

FALKEN

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i was fine tuning the bias and playing the guitar with several tube sets and different settings for the last few days. I was wondering what you might listen for when fine tuning amp bias. This was with el34s (if it makes a difference?). Also I was wondering if the gain hitting the amp effects the setting...like will playing different guitars lead me to a different setting?
 
FALKEN said:
i was fine tuning the bias and playing the guitar with several tube sets and different settings for the last few days. I was wondering what you might listen for when fine tuning amp bias. This was with el34s (if it makes a difference?). Also I was wondering if the gain hitting the amp effects the setting...like will playing different guitars lead me to a different setting?
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Perhaps you've just forgot to mention it, but I hope you're not adjusting your bias with only your ears!!! Hope you've got a scope or at least a bias meter to ensure it's running the safe range...

Assuming you do know that stuff and you're within your maximum, it's down to personal taste I'm afraid and no one can tell you what you like.

Gain (again assuming that you're talking preamp gain) doesn't really come into it, as the bias only really affects the power section. You might find you will change your settings because your amp sounds a bit different, but I wouldn't go as far as changing bias when swapping guitars.

Just my 2c!
 
generaly speaking as you decrease the bias the tubes turn on "faster" so the sound tends to have more body... thicker... creamier... conversly if it's increased it has more edge... sharper... but be careful how far you push it... unless you like buying several sets per year... and remember that what your doing is applying a negative voltage... so less bias is moving towards zero... conversely adding more negative voltage moves deeper in the voltage sense and shuts the tube off more... didnt want to belabour the point but some have a hard time with the adding more negative idea... and yes do check it with a bias probe or similar to make sure you dont go too far with it... what amp are you working on??? there's a simple mod that can be done on some amps that basicly adds the bias probe to the circuit for easy adjusting...
 
ok about negative voltage..... a reading of 40 ma is hotter than 35? or do I have that backwards because its negative?

I am working on a orange or-120 which is cool because it has the hum eliminator pot as well as the bias pot. no need to add the 1 ohn resistors because I got me a TAD Bias Master.

So as you can see I am pretty much a NEWB at this and was hoping to get some insight as to what to listen to when setting this thing.
 
FALKEN said:
ok about negative voltage..... a reading of 40 ma is hotter than 35? or do I have that backwards because its negative?

I am working on a orange or-120 which is cool because it has the hum eliminator pot as well as the bias pot. no need to add the 1 ohn resistors because I got me a TAD Bias Master.

So as you can see I am pretty much a NEWB at this and was hoping to get some insight as to what to listen to when setting this thing.
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Nice amp! And nice meter too.

dementedchord is totally right but don't misconstrue negative voltage application with the ma you are reading - 40 IS hotter than 35. I don't know the specs of your amp though, 40-45 is the max I would go on my 5150. But 100% agree - hotter = creamier and thicker, colder = harsher, a bit more clunky on the cleans. Some amps are fixed really cold (like Mesas, and like my 5150 before I modded it) and it seems to be part of their "sound"... not that you'll turn your orange into a mesa if you dial it to 16 per tube hehe.

What I can say is I noticed a huge difference going from cold to hot, but I guess it depends on where you are now and where it was from the factory as to if you'll really notice. IE maybe your orange was actually biased properly in the factory, so you won't experience a huge difference.

Check out www.eurotubes.com for some sweet videos and heaps of info. Plus Bob sells JJ tubes which kick total ass and he's a really nice dude in general...
 
yep 40ma is hotter than 35ma... remember your reading current at this point... the only orange schemo i have around here isthe 1970's vintage120... so dont know if the supply rails are close... but this shows a rail of 450V... assuming this the current draw should be @37ma/tube so your well within the spec using 34-40... remeber that the hum balance and bias adjust are interactive... so double check each and give a little time to stablize before closing it up ...
 
hey - thanks for that info!

for some reason I seem to like it right around 35. Over that sounded a bit harsh, and over 40 gave a cooking smell. Right at 35 was the only setting that gave my strat that real singing STRAT sound. If that makes any sense.

so thats what i went with but maybe I wasn't listening for the right thing....

I went right for the point where if I slammed a power chord on 10 (on the strat) it would break up slightly but still sound rather clean. like right on the edge of breakup. that was with the amp volume at about 1/3.

sound good or no?
 
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