#1
So, I've done quite a bit of reading and i still cant get my head around "BIASING". It sounds as if this is a method of distributing voltage across the tubes evenly. So my question is this really.

If i have "tubes" in my amp right now how would switching them out with new tubes unbalance that load? Also, is it necensary to BIAS the amp? Can i not simply order new tubes pull th old ones out and drop the new ones in? I've read that biasing is only necesary when changing brands of tubes. Is there truth to that? Where can I find a good writeup on "Changing Tubes in a Tube amp" If you google that i've read most of the posts on the 1st page that it turns up but hey, i'm a junkie when it comes to forums.

Whatever you post i will just take with a grain of salt so feel free to offend me. (Stupid n00b, if you have to ask you should take it to a tech). ~ Not saying thats a bad answer and it may come to that but over the past 15 years i've dug into enough electronics and have soldered enough to know that most of the time you just have to dig in and not be scared. Seams to be a bit different story with Tubes tho as there are some pretty deadly voltages we are dealing with.

Thanks all for any "INFORMATIVE" information. =)
#2
6505's have a non-adjustable fixed bias. So yeah, you pretty much need to drop your new power tubes in.
#3
Thanks Strats, i have indeed read that very thing. Can you explain to me what this means? What is this crazy thing called BIAS? Why does it change from tube to tube?
#4
here, i found this. This should explain in easy terms what biasing is.

http://answers.yahoo.com/question/index?qid=20071120063702AAZly50

should help a bit


EDIT:


Quote by surjer
Thanks Strats, i have indeed read that very thing. Can you explain to me what this means? What is this crazy thing called BIAS? Why does it change from tube to tube?



Why The tube bias changes from tube to tube, is best explained like a lightbulb.

Not every lightbulb is build the same, even though they are very very close. Some last for 5 years, some burn out in a few weeks.

Same thing for tubes, Not each one has the exact same optimal current. just because it's impossible to manufacture them all perfectly the same
It's over simplified, So what!

Quote by eGraham
I'm going to be on top of what is called a knob
Quote by theguitarist
Big ones can be fun in some ways but generally, they are a pain in the ass.
Quote by Wolfinator-x
I don't know what is going on in this thread or why I have an erection.
Last edited by Obsceneairwaves at Dec 11, 2011,
#5
Quote by Obsceneairwaves
here, i found this. This should explain in easy terms what biasing is.

http://answers.yahoo.com/question/index?qid=20071120063702AAZly50

should help a bit


That's a bit more into it then I think he needs... Haha

Anyway, the "bias" of the amp is how hard/hot the amp runs the power tubes. Generally the hotter the tubes run, the better they sound. However, running the tubes too hot can dramatically reduce their life as well. So it's about finding a balance between sound quality and tube life. That's what biasing an amp is for. It's generally recommended that (if you can) you bias your amp every time you change power tubes to get the ideal bias for those tubes, because every set of power tubes is different.

However, your 6505 doesn't have an adjustable bias. It's set where it's at and can't be changed without modding the amp. This shouldn't be a problem because 6505's are biased from the factory very cold so you don't have to worry about any new tubes going in. Just swap them in, everything will be fine.
#6
Quote by Strats&Cats
That's a bit more into it then I think he needs... Haha



It's over simplified, So what!

Quote by eGraham
I'm going to be on top of what is called a knob
Quote by theguitarist
Big ones can be fun in some ways but generally, they are a pain in the ass.
Quote by Wolfinator-x
I don't know what is going on in this thread or why I have an erection.
#7
Absolutely awesome information obscene, I followed a link to Tube Depot and found this explanation which is essentially the same post but has nifty little graphics. This was what i was after.

http://tubedepot.com/whisbipo.html

Now, this leads me to my next question of the BIAS voltage.

Strats - You mentioned the amp i have is biased pretty cold. I have heard that from my week of googling. Does this mean the BIAS voltage is actually a higher voltage as to repel more electrons? Also, if that grid is repelling the electrons where do they go? I would think if they are not making it to the plate then that are just bouncing around in there creating more heat? Maybe by cold this means less current on the grid so it lets MORE electrons through?

Sorry for the super technical questions but i just really like the "tinkering" side of this as well.

Sounds like finding that optimal bias would improve your tone quality. maybe warm it up a bit? Wondering how "OFF" the factory BIAS is to the tubes that are in it. I've heard these are pretty "COLD" tubes to begin with. BIAS these tubes or replace and re-bias?

Sooo, many options with a nice tube amp. Gotta love the vyper, turn it on and just start hitting random buttons to reveal a completely different sound! haha...
#8
here is a related thread

https://www.ultimate-guitar.com/forum/showthread.php?t=1502708&highlight=6505+bias

I didn't feel like retyping anything

Too hot a bias and your tone will sound muddy and warbly.

hot =/= better

Most Peavey amps are biased cold, the 6505 is no exception.

The USA 6505+ came with a bias pot and test points but the test points cannot be trusted and the bias pot did not have enough range and basically did nothing.

The 6505+112 does not have this feature that I am aware of.

You would have to get the amp modded to get a true biasing feature.

You don't bias tubes, you bias amps.

I have a blog that goes into a lot of detail on what to do if you have a fixed bias amp and have to manual bias your amp
#9
Thanks 311, I didnt mean bias the tubes, typed too fast. I think i am starting to understand the term a little better now. Definately interesting stuff. Had no idea what those tubes actually did or how technically they effected sound.
#11
Quote by surjer
Absolutely awesome information obscene, I followed a link to Tube Depot and found this explanation which is essentially the same post but has nifty little graphics. This was what i was after.

http://tubedepot.com/whisbipo.html

Now, this leads me to my next question of the BIAS voltage.

Strats - You mentioned the amp i have is biased pretty cold. I have heard that from my week of googling. Does this mean the BIAS voltage is actually a higher voltage as to repel more electrons? Also, if that grid is repelling the electrons where do they go? I would think if they are not making it to the plate then that are just bouncing around in there creating more heat? Maybe by cold this means less current on the grid so it lets MORE electrons through?

Sorry for the super technical questions but i just really like the "tinkering" side of this as well.

Sounds like finding that optimal bias would improve your tone quality. maybe warm it up a bit? Wondering how "OFF" the factory BIAS is to the tubes that are in it. I've heard these are pretty "COLD" tubes to begin with. BIAS these tubes or replace and re-bias?

Sooo, many options with a nice tube amp. Gotta love the vyper, turn it on and just start hitting random buttons to reveal a completely different sound! haha...


If you want to know more about tubes (not just in guitar amps, but in all amps) look around. There's articles all over the place.

As for your 6505, the bias doesn't really matter. It's a very front end (preamp tube) heavy amp. The power tubes don't matter nearly as much. Not to say a good set of power tubes won't make a clear difference, but It's not as important as say a marshall 18w.

And biasing tubes "cold" just means the tubes are under less voltage, and as a result, less stress. This usually also means less breakup, which you wouldn't want in a metal amp like the 6505 anyway.
Last edited by Strats&Cats at Dec 14, 2011,
#12
So, I can drop in any set of 6l6s into my 6505 and all is well? Sorry to barge in, just curious. :p
*insert witty statement here*
#13
^ Well, you still want to get tubes of the same brand and ask for a matched set.

I've found that even when 'matched' tubes are requested - they still vary quite a bit.


Quote by surjer
Hey 311, think you can point me to that blog? Would love to check it out..

http://profile.ultimate-guitar.com/311ZOSOVHJH/blog/80083/