#1
When I read about amps here on this forum, it says "new amps need to bee biased"... My 800 is from 1983... When I bought new powertubes I asked the "amp-guy" in the store about rebiasing my amp, and he said that its really not nessesary and that he didnt even got the equiptment to bias the amp in the store... So I ask you here at UG, DO I NEED TO REBIAS MY AMP ?

Gibson Les Paul Standard
Takamine G Series 6&12 string accoustics

Marshall JCM 800 50w 1987 (4 input)
Marshall 1936 Cab

Jim Dunlop CryBaby
MXR 10 band EQ

R n'fn' R!
#3
meh... my amp sounds incredible
Gibson Les Paul Standard
Takamine G Series 6&12 string accoustics

Marshall JCM 800 50w 1987 (4 input)
Marshall 1936 Cab

Jim Dunlop CryBaby
MXR 10 band EQ

R n'fn' R!
#4
It's not the sound.......bias is the power disribution through the tubes . If your amp is not properly biased then your tubes won't last, or could simply fail. There's plenty of info on it --- just do a search.
This only applies to output tubes----preamp tubes do not need to be biased
#5
I know what the bias is... my question was if those old amps really need to be biased
Gibson Les Paul Standard
Takamine G Series 6&12 string accoustics

Marshall JCM 800 50w 1987 (4 input)
Marshall 1936 Cab

Jim Dunlop CryBaby
MXR 10 band EQ

R n'fn' R!
#6
You should bias all tube amps when you replace the power tubes, but you don't HAVE to.

With an amp more than 15 years old though, it's a good idea to take it to a tech in any case.
I'm not very active here on UG currently.
I'm a retired Supermod off to the greener pastures of the real world.
#7
Quote by Sl4Sh_Jr.
I know what the bias is... my question was if those old amps really need to be biased


They do, if you are putting in a new set of power tubes with either a different rating or different tubes altogether (ie replacing EL34's with 6V6's). If your amp is 'class A' it is self-biasing and if you put in the same type of tube with different power ratings you shouldn't have to have a tech rebias them, but you still do if you are changing tube types. Change "amp-guys" this guy obviously didn't know what the hell he was talking about.
Gibson SG Standard
Orange Rocker 30 combo
Fulltone OCD
EH Holy Grail
#8
^ yeah. And you said your amp sounds incredible now...well youd be suprised how much of a difference it makes.
#9
Quote by rockxwl
They do, if you are putting in a new set of power tubes with either a different rating or different tubes altogether (ie replacing EL34's with 6V6's). If your amp is 'class A' it is self-biasing and if you put in the same type of tube with different power ratings you shouldn't have to have a tech rebias them, but you still do if you are changing tube types. Change "amp-guys" this guy obviously didn't know what the hell he was talking about.



Hey, if that was directed at me then you are mistaken. I said get a new tech and have your amp checked. The thread starter said his guy didn't even have what he needed to do the job. He also made no mention of whether or not the tubes were direct replacements or not. I have been playing and taking care of my own equipment for thirty years. The advice I gave is correct. If you were'nt addressing me ----sorry
#10
Quote by REBARMAN99
Hey, if that was directed at me then you are mistaken. I said get a new tech and have your amp checked. The thread starter said his guy didn't even have what he needed to do the job. He also made no mention of whether or not the tubes were direct replacements or not. I have been playing and taking care of my own equipment for thirty years. The advice I gave is correct. If you were'nt addressing me ----sorry


No no no I was directing the "amp guy" comment at the threadstarters first post, about how the amp-guy at his local store said he wouldnt need to rebias and that he didnt have the equipment to check anyway. Sorry for the confusion, bro
Gibson SG Standard
Orange Rocker 30 combo
Fulltone OCD
EH Holy Grail
#11
Biasing your amp will change the tone, since you're applying either more or less voltage to the plate. You could bias it hotter or colder, and it'll change how your amp sounds (how much... depends on your personal sensitivity to tone). Running your tubes either too hot or too cold will shorten the life of your tubes. Or you might just be lucky and had replacement tubes which get the right amount of plate voltage.