#1
i think this might be a stupid question but i get this feeling like some amps cant be biased. yes there are fixed bias amps like mesa but thats not what im asking.

im asking if an amp doesnt have an external bias test point, is there something on the inside that you can use (internal bias point?)?

ive also read that you use a small screwdriver to adjust it, but it is advertised as if this isnt the case with all tube amps. so do all tube amps bias pretty much in the same manner?
Schecter C-1 classic
Takamine GS330S
Roland microcube FTW!
#2
The only amps that are biasable with a screwdriver that ive heard of are the Visual Sound amps. If you take it to a tech, im sure thay could bias it if u need it.
#3
Check this out should answer a few of your questions
http://acruhl.freeshell.org/mga/main/bias.html
Tom Anderson Hollow Classic
72 thin line tele

Barber trifecta fuzz
Mi audio Crunch Box
Clyde Wah
Barber Burn Unit
Ocean efx Texas deuce
Boomerang chorus delay
Barber ltd


1971 Pro reverb
Fender acoustasonic
Fender super champ xd
#4
on those that can be adjusted, there's a trim pot on the inside that you can adjust with a screwdriver.
Gibson SG Standard + 18volt EMG-81 & 85
Mesa/Boogie Mark IV + Recto 2x12
Keeley Modded BD-2
Vox V847a
Quote by one vision
Bureaucrats gonna crat.

Recognised by the Official EG/GG&A Who To Listen To List 2008
#5
Quote by qotsa1998
The only amps that are biasable with a screwdriver that ive heard of are the Visual Sound amps. If you take it to a tech, im sure thay could bias it if u need it.


The randall MTS amps can be also biased with a screw driver.
And that's on the outside on the back of the amp.
Clickie =]

If you look to the bottom right, there'll be a 'MTS back features: MPG/WMV'
And that'll explain everything.
#6
well thats kind of what i was getting at. i noticed that the randall MTS has that, and a framus cobra has test points in the back (not sure on how to adjust it tho). im asking if an amp doesnt have external bias points does this mean it will have them inside so a regular guitarist can bias it or is it really necessary to take it to a tech b/c they have special gear for this. i thought all i needed was a multimeter and something to turn the thingy that adjusted the bias like a screwdriver.

so lemme ask again.

are all amps biasable?

and if the test points arent inside, does that mean i have to take it to a tech to bias it?

it seems with the randall MTS that the lil screwdriver thing is a big deal. like its a selling point of the amp so that got me confused and wondered if that is not the case with most amps.
Schecter C-1 classic
Takamine GS330S
Roland microcube FTW!
#7
In tube amps, in theory, yes. All amps are biasable.
In solidstate amps, no.
Unless I had a Randall MTS or something with external bias points, I wouldn't try biasing the amp myself. I don't trust myself with electronics as much as I trust a tech.
#8
Any tube amp can be biased. Some are easier to bias than others.
The ones you describe are very easy to bias since they have external bias points and pots.
Other types of amps have internal test points and pots; some have no test points and you need to use your own resistors to check the bias.
Some amps are fixed-bias in the old sense of the word or are cathode -bias, and you can only change the bias by physically changing parts inside the amp.
#9
Quote by giternator
well thats kind of what i was getting at. i noticed that the randall MTS has that, and a framus cobra has test points in the back (not sure on how to adjust it tho). im asking if an amp doesnt have external bias points does this mean it will have them inside so a regular guitarist can bias it or is it really necessary to take it to a tech b/c they have special gear for this. i thought all i needed was a multimeter and something to turn the thingy that adjusted the bias like a screwdriver.

so lemme ask again.

are all amps biasable?

and if the test points arent inside, does that mean i have to take it to a tech to bias it?

it seems with the randall MTS that the lil screwdriver thing is a big deal. like its a selling point of the amp so that got me confused and wondered if that is not the case with most amps.


Yes, all tube amps can be biased. Cathode Biased amp do it automatically. The only high powered cathode biased amp that I know of is the Budda Superdrive 80.

Mesa/Boogie amps can be biased as well by either swapping out the fixed resistor the sets the bias or swapping out the fixed resistor with a variable resistor, which is what a potentiometer (pot) is.

You don't have to carry it to a tech to have it biased. You can buy a bias probe that reads the Cathode Current and Plate Voltage and learn how to do it yourself. The Weber Bias rite is a great tool to use and will pay for itself after you change your power tubes 2 or 3 times.
#11
Quote by Roc8995
Any tube amp can be biased. Some are easier to bias than others.
The ones you describe are very easy to bias since they have external bias points and pots.
Other types of amps have internal test points and pots; some have no test points and you need to use your own resistors to check the bias.
Some amps are fixed-bias in the old sense of the word or are cathode -bias, and you can only change the bias by physically changing parts inside the amp.



what?! your saying in a fixed AND cathode biased amp you have to change parts to change the bias? as in for a fixed bias to change its range u have to change a part....that makes sense but a cathode biased amp too?

and how would u go about testing with the resistors?

Yes, all tube amps can be biased. Cathode Biased amp do it automatically. The only high powered cathode biased amp that I know of is the Budda Superdrive 80.


so..... you dont bias a cathode amp because u dont need to or it just isnt necessary to function safely (as in bias it to sound better and not b/c itll meltdown)? u can adjust it tho right?

and what determines an amp is cathode or not?

You don't have to carry it to a tech to have it biased.


so this means u can bias ANY amp with a lil reading involved right? as well as proper equipment which the average person can buy?


sorry about all the questions but this is getting confusing and complicated.
Schecter C-1 classic
Takamine GS330S
Roland microcube FTW!
#12
Quote by BAoxymoron
Diezels are easily biased heres how
http://diezel.typo3.inpublica.de/tech-corner.3.0.html



yeah thats exactly what a randall MTS is like. some amps are this easy, my question is if the amp doesnt have this feature how hard is it to bias, so hard that a tech is necessary or can u just read up a lot on it and do it?
Schecter C-1 classic
Takamine GS330S
Roland microcube FTW!
#13
Quote by giternator
what?! your saying in a fixed AND cathode biased amp you have to change parts to change the bias? as in for a fixed bias to change its range u have to change a part....that makes sense but a cathode biased amp too?

if you're going by mesa's definition of "fixed" and cathode biased, then there is no way to bias it. simply because they thing you don't need to. they probably set the amp at a constant bias that works for most brands, but none optimally. you don't have to install a bias pot in a cathode-biased amp if you don't want to.

Quote by giternator
so this means u can bias ANY amp with a lil reading involved right? as well as proper equipment which the average person can buy?

of course. i mean, somebody has to do it. it's not done by robots or anything.
Gibson SG Standard + 18volt EMG-81 & 85
Mesa/Boogie Mark IV + Recto 2x12
Keeley Modded BD-2
Vox V847a
Quote by one vision
Bureaucrats gonna crat.

Recognised by the Official EG/GG&A Who To Listen To List 2008
#14
Quote by UnsignedRecords
if you're going by mesa's definition of "fixed" and cathode biased, then there is no way to bias it. simply because they thing you don't need to. they probably set the amp at a constant bias that works for most brands, but none optimally. you don't have to install a bias pot in a cathode-biased amp if you don't want to.


of course. i mean, somebody has to do it. it's not done by robots or anything.


lol man youve always been a great help to me and your younger than me -_-. im guessing by your sig your name is jon? well thanks a lot jon. im adrian. now were acquainted

but anyways. so your saying cathode bias'd amps cant be adjusted w/o adding something to it? im sorry im persistent but it wasnt very clear.

and yeah i guess thats true about the robots but i was just wondering that if you needed college level course for it (exaggeration). i guess not since this is really old tech anyways (tubes).
Schecter C-1 classic
Takamine GS330S
Roland microcube FTW!
#15
i just pick up bits of stuff from here and there really...
and yeah, as roc put it, cathode-biased amps' bias can't be changed without changing components within the amp.

a little light reading, maybe an instructional video, or just watching a tech do it once and you should be in good shape to do it yourself.
Gibson SG Standard + 18volt EMG-81 & 85
Mesa/Boogie Mark IV + Recto 2x12
Keeley Modded BD-2
Vox V847a
Quote by one vision
Bureaucrats gonna crat.

Recognised by the Official EG/GG&A Who To Listen To List 2008
#16
thanks a lot man. im all cleared up now.

but just one last question

im planing on getting a VHT (boy how i change opinions alot) and im pretty sure thats gonna be it (but knowing myself, there is no validity to my word ) so basically im concerned on how im going to bias my VHT. most likely a deliverance or CL. im guessing it has internal bias test points and pots. i seen someone on youtube doing a vid after they biased ("VHT deliverance 60 dynamics"). so it must be relatively easy....or so i hope.
Schecter C-1 classic
Takamine GS330S
Roland microcube FTW!