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Old 07-07-2005, 07:59 PM   #1
Shredhead
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how can i re-bias my amp after new power tubes?

how can i re-bias my amp after new power tubes? do i have to do it every time i replace the power tubes? cani do it at home ? if so how? thanks!
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Old 07-07-2005, 08:00 PM   #2
Aes820
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You dont bias tubes.
You bias your amp, to suit the tubes.

What is the make and model of your amp and what tubes have you got in it?
We'll be able to further tell you what needs to be done once we know this.

But in most cases I would alsways reccomend you leave biasing to someone who knows what they are doing. Like an amp tech.
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Old 07-07-2005, 08:07 PM   #3
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Quote:
Originally Posted by Aes820
You dont bias tubes.
You bias your amp, to suit the tubes.

What is the make and model of your amp and what tubes have you got in it?
We'll be able to further tell you what needs to be done once we know this.

But in most cases I would alsways reccomend you leave biasing to someone who knows what they are doing. Like an amp tech.
Sovtek Mig 50

original tubes...


what will it sound like if it is not biased properly?
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Old 07-07-2005, 08:16 PM   #4
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Your amp will take a pair of 6L6 or a pair of 5881 power tubes.
At the moment it is probably running 6L6s.

You will need to take your amp to a tech to have it's bias voltage adjusted to suit the new tubes whenever you change power tubes.

An incorrect bias voltage can cause problems with your amp. Excessive heat, pops, and crackles. Maybe even shorted out tubes and blown fuses, or cooked screen grid resistors..

Although some small variations can give differnt results such as a warmer tone and a lowered amount of headroom at the expense of some tube life.
Or to prolong tube life and increase output power at the expence of tone warmth.

The point of biasing an amp is to reach a compromise inside the amp between a good tone and good amplifier efficiency. An amp manufacture would have already figured out this ideal point and built the rest of the amp with this in mind.
A tech will be able to adjust your amp to this point so that it is suitable for the tubes you are running.

It is usually a very simple procedure. Many amps have features built into them where a bias adjustment is as simple as a check of a voltmeter and a turn of a trimmer pot provided you stick with using the same type of tubes.
But because of the high voltage in your amp that can still linger around long after the amp has been turned off, it is best left to a tech.
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Old 07-07-2005, 08:20 PM   #5
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yeah i think you are right, i'll take it somewhere...sounds too scary to me..heh..thanks!
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Old 07-07-2005, 08:22 PM   #6
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all depends on how your amp is designed. I'm not overly familiar with the Sovtek Mig series... i'm sure you can find out more about it online though. basically if it has a bias trim pot, get it rebiased. if not... well... you can't bias it then, so don't worry about it.
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Old 07-07-2005, 08:26 PM   #7
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Originally Posted by animephreak
all depends on how your amp is designed. I'm not overly familiar with the Sovtek Mig series... i'm sure you can find out more about it online though. basically if it has a bias trim pot, get it rebiased. if not... well... you can't bias it then, so don't worry about it.
i looked and couldnt find one..is it ever inside somwhere...the trim pot
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Old 07-07-2005, 08:28 PM   #8
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One of my band mates has a Mig 50.
It's got a trim pot in it somewhere. But I've never looked at it really. He took it into a tech and got some Mesa 6L6Gcs in it.

It goes alright. But its a weird amp.
It really is quite quiet while under halfway on the volume dial. But as soon as you turn it past halfway it just roars. And peels paint off the walls.
Does yours do the same, threadstarter?
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Old 07-07-2005, 08:29 PM   #9
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on most amps the trim pot is actually inside the amp chassis. Even on amps with external bias test points they still usually put the trim pot in an inaccessible place so you don't move it accidentally.

you'd want to find schematics of the amp and see if there is mention of a trim pot.
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Old 07-07-2005, 08:37 PM   #10
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mine doesnt really do that...it starts t oget really loud alittle earlier..but it is LOUD i mean really LOUD...maybe the russians mees up the russian to english translation when they said it is 50 watts...heh...i'l probably take it in somehwere and get it done..any suggestions on tubes? i would like to tighten up the low end some..but still have allot of distortion...any tips on that? thanks! i'm going to replace all the tubes btw
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Old 07-07-2005, 08:39 PM   #11
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email doug at dougstubes.com or bob at eurotubes.com I have heard of the Mig 50 many times before, so i'm sure they have dealt with one before and can recommend you some stuff.

what kinda tubes are in it now?
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Old 07-07-2005, 08:53 PM   #12
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Originally Posted by animephreak
email doug at dougstubes.com or bob at eurotubes.com I have heard of the Mig 50 many times before, so i'm sure they have dealt with one before and can recommend you some stuff.

what kinda tubes are in it now?

the stock ones...whatever it came with...i assuming Sovtek tube
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Old 07-07-2005, 10:26 PM   #13
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Quote:
Originally Posted by Shredhead
the stock ones...whatever it came with...i assuming Sovtek tube
sovtek tube are good as long as you get the GOOD preamp tubes. The current production 6l6 tubes are pretty nice , and the 12AX7WC and LPS models are very passable preamp tubes, especailly compared to their WA and WB models, which blow.
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