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I would like to know what the advantages and disadvantages of biasing your amp to anything other than the factory recommended settings are. My Marshall has a recommended bias voltage of 90mV. Would it hurt anything to raise that voltage and does it really affect your sound at all? Thanks for the input.
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Re: Question for the amp biasing gurus.
I'm sure true tech heads will have other stuff to say.
But, I'm pretty much sure bias is related to the particular tube. Not what what the manufacturer of the amp would like, unless you are using a tube that they have issued.
Different tubes in the same amp bias out differently.
If they are recommending a particular voltage with the tubes they are referring, increasing voltage over that will liekly reduce life of the tubes. May improve the sound a bit, as I seem to like my amps biased a litte hot...
Marshall is notorius for biasing amps cold from the factory to get them through the warranty period without trouble...
[ January 26, 2003, 06:01 PM: Message edited by: Cleveland Metal ] -
Re: Question for the amp biasing gurus.
bias voltage is generally read at the tubes... even if you use the transformer shunt method, your tubes affect the voltage. So, no matter how you change the voltage for different tubes, 90mv is what marshall recommends apparently... and that sounds off to me... about twice what I would think. Generally speaking, tubes fall into a range of acceptable bias. Too cold, and the tube lasts forever but sounds gravelly and has too much headroom. Too hot, tubes don't last as long and have less headroom. The plates are those grey flat things in the middle of the tubes. Once you set the bias where you want, WATCH THE PLATES - if they start glowing red or orange, shut the amp off - you're burning the tubes up.
PeteComment
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Re: Question for the amp biasing gurus.
DON'T ADJUST ANYTHING!!!!!
have a professional tech bias your tube sockets for new tubes only!!!! and when you replace them, if you like the sound of those tubes, get a matching set. i.e. the numbers printed on the tubes themselve relate to the bias of the tube. if you get a set of tubes with the same printed numbers (usually around the base of the tube) you will not have to re-bias your tube sockets. if you never want to have to worry about biasing tube amps, buy a boogie and only use boogie tubes.
for more info, check out www.mesaboogie.com and check the articles section on the subject.Comment
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Re: Question for the amp biasing gurus.
Few questions for the last poster...
1) How is boogie's 'fixed bias' setup better than other amp companies? what's the difference?
2) how do you set the bias on a tube socket?
This oughta be good....
PeteComment
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Re: Question for the amp biasing gurus.
FWIW I called Lord Valve and asked about getting a biasing pot put in. He told me not to screw with it just leave it alone.1+2 = McGuirk, 2+4 = She's hot, 6-4 = Happy McGuirkComment
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Re: Question for the amp biasing gurus.
1) How is boogie's 'fixed bias' setup better than other amp companies? what's the difference?
i'm not saying its better. boogie is pickier about the tubes it puts its name on. they pre set the bias of each amp the same and only sell tubes that fall withing the range of that bias. so you don't have to take it to a shop and spend the money on having it biased
2) how do you set the bias on a tube socket?
there are adjustment screws somewhere near each socket, or resiters that have to be changed out. usually on the unerside of the socket so you have to pull the circuit board out of the chasis. it just depends on the make and model. but you have to set it using a voltmeter or ocilliscope and i recomend not doing it yourself!Comment
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Re: Question for the amp biasing gurus.
Not sure what amp you're talking about Buzzsaw, but if it's a boogie - LV matches tubes like boogie does, and provides em. Personally speaking, i like being able to get every last drop of tone out of my amp, and adjustable bias lets you set where your tubes are idling within the proper operational range.
I just think the boogie 'bias' setup is Bullsh!t and a way to keep you buying certain brands of tubes - whether they are boogie or LV's matched ones.
PeteComment
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Re: Question for the amp biasing gurus.
boogie doesn't make tubes, and neither do most companies. most companies buy them in bulk from russia, china, the czech republic. (tubes were used in all the military electronics when russia was working with Electro Magnetic Pulse technology, because tubes were not effected by the pulse) so they have been selling them off in bulk to groove tubes, fender, sovtek, svetlana, boogie, etc... boogie just buys the ones that fall into "thier" bias range (which is quite small) which really doesn't matter because they are all around the same price.
[ January 27, 2003, 04:09 PM: Message edited by: Dreamland_Rebel ]Comment
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Re: Question for the amp biasing gurus.
<font size="2" face="Verdana, Helvetica, sans-serif">Boogie uses the same friggin' tubes you can buy from online tube vendors at much better prices... you're paying for a guy from boogie to wipe out the old logo and put a boogie one on there. If you want to say that boogie tubes are tested more - well, I can't think of any new tube dealer that doesn't offer a warranty on their tubes... a bad tube is going to fail pretty quickly out of the box.Originally posted by Dreamland_Rebel:
1) How is boogie's 'fixed bias' setup better than other amp companies? what's the difference?
i'm not saying its better. boogie is pickier about the tubes it puts its name on. they pre set the bias of each amp the same and only sell tubes that fall withing the range of that bias. so you don't have to take it to a shop and spend the money on having it biased
2) how do you set the bias on a tube socket?
there are adjustment screws somewhere near each socket, or resiters that have to be changed out. usually on the unerside of the socket so you have to pull the circuit board out of the chasis. it just depends on the make and model. but you have to set it using a voltmeter or ocilliscope and i recomend not doing it yourself!
By the way, *EVERY* amp maker sets their bias the same - some use cathode bias, some use fixed bias. Boogies use a fixed bias scheme where there is a resistor soldered into place. I had a '68 princeton with the same biasing setup - it's non-adjustable, unless you want to remove the resistor and replace it, which I did in my amp. All Boogie wants to do is make sure you buy their tubes... and by the way, their amps are consistently biased cold - this makes their tubes last longer, but their amps not sound as good as they could. It sure makes those high-performance relabeled boogie tubes last longer tho.
Biasing isn't done at the sockets - most amps have either on the main board or a board off to the side the bias supply that has a resistor that has to be changed out (on a boogie) or a pot installed in place of the resistor or tweaked. The only amps I've seen that had the bias resistor at the socket was a cathode bias setup, which self regulates and doesn't need adjustment or replacement.
One reason you might want to check your bias even if you had a magical boogie bias amp is that a resistor is what sets bias... and resistors change value over time... plus to my ear, an amp that runs cold bias sounds like crap compared to one that is running slightly hot - but boogie will never let em leave the factory a little hot, since that will cut down on tube life a bit.
PeteComment
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Re: Question for the amp biasing gurus.
Also, pricewise - go to www.tubestore.com and compare their prices with Boogies. at least $10 cheaper per pair of 6L6s depending on what you get. The only thing I saw on there that was priced that close seemed to be EL84s and preamp tubes.
I have a boogie, but I feed it NOS Tungsol 5881s so far... better than anything boogie currently sells in any event, but a lot pricier. [img]images/icons/grin.gif[/img]
PeteComment
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Re: Question for the amp biasing gurus.
<font size="2" face="Verdana, Helvetica, sans-serif">Hahahahahahahahahahahahahahahahah, gasp, hahahahahahahahahahahahahahahahah, hack hack gasp,boogie is pickier about the tubes it puts its name on
hahahahahahahahahah.... oh god... hahahahahaha....Comment
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Re: Question for the amp biasing gurus.
yeah, they are the same tubes, but boogie has tested them to fall within their set bias and they have good quality control. (for their power tubes at least, the pre's arn't any better at all)but they're warnted aswell. and of coarse i've had my amp biased, actually i had it rewired for EL84's and biased nice and warm. everybody should have their amp biased by a professional amp tech when they first replace thier tubes. and for most amps should everytime unless they get the same rated tubes.(again, located usually on the plastic base before the prongs, save yourself a visit to the amp doctor kids.) and yes, resistors don't last forever. but the 10 bucks you save, over time, will not add up to the 50+/hour bench charge, plus new tubes. but thats up to the owner, i could care less if you use boogie, boogie tubes, both, or none. it really doesn't matter as long as your rig sounds good. i love the whole jmc line, and any other great sonding amp. and to be honest i feel like the whole nomad line was a complete embarrasment. really bad move on their part. and most of the time a good cabnet can pass off even a sh1tty head in a live situation. i just didn't want the guy messing up something by trying to bias his own head. i buy boogie tubes casuse i like the different versions they carry and how they sound with different heads. i was actually able to experiment with them at work, since i could switch out boogie productes with booogie productes. but thats a different topic.
OklaStrat, what type and kind of rig ya got?Comment
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Re: Question for the amp biasing gurus.
Prolly simpler for him to answer what kinda rig he HASN"T had..haha...
Myself, I have a Bradshaw CAE3+se and VHT 2150... (in case that was coming next). But, have stupidly owned most everything around it seems except an SLO...Comment
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Re: Question for the amp biasing gurus.
Pete,
It's a MK3 simul class, he said the tone enhancement thing is bull**** and screwing with biasing severly shortens tube life and can be dangerous, his words not mine.
Of course he said he's got tons of different tubes to pick from if i wanna start playing with tone.
If it's simply a resistor I can do that myself if I knew which one and what value I should be plugging in.
While we're talking about tubes I may have a hookup for old US tubes, but it's still in the works.1+2 = McGuirk, 2+4 = She's hot, 6-4 = Happy McGuirkComment
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