Tinkering with Bias?

T

teledude

New member
Hello:

Has anyone experimented with changing the bias setting to "hotter" or "colder" than normal? I have a Fender Twin...it lets you set the bias yourself with a voltmeter(suggests 60mvDC). I have heard that changing the bias can dirty-up or clean-up the sound of the amp. I have also heard that changing the bias can destroy the tubes/input power-supply :smack: Has anyone tried this???

I have read some very useful info on this site...thank you all for sharing.

teledude
 
Re: Tinkering with Bias?

I like to have the chassis on a bench, plugged into a cab and with a guitar plugged into it. Just strum the guitar with one hand, while the other hand nudges the bias pot, somewhere in the middle of it's travel. If you know how your amp sounds when it's at it's best, you'll hear where the bias pot should be set. When the amp is boldest, punchiest, and tightest is when it's biased correctly. Either direction away from that, and the amp sounds feeble or too pushed, and it's loses it's punch. It's best to do it with a bias tool and multimeter, or even better...an oscilloscope, but if you do it by ear, just be careful not to turn the gray plates red. Just find the nicest tone you can, then leave it.
 
Re: Tinkering with Bias?

Gearjoneser said:
I like to have the chassis on a bench, plugged into a cab and with a guitar plugged into it. Just strum the guitar with one hand, while the other hand nudges the bias pot
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GJ, I understand that you have plenty of experience working with and modding your equipment but with all of the youngsters on this board it's kind of reckless to suggest that you have one hand in the amp and the other on the strings of your guitar with the power on. These kids don't understand basic electricity and circuits and that scenario could easily turn lethal.

WARNING: It is not a good idea to touch your guitar strings when you have your other hand inside the amp or near a live amp circuit board. There are LETHAL high voltages on the board and you could inadverdantly complete a circuit to ground through your body and across your chest. This can KILL you. Please do not attempt this without supervision or unless you are extremely experienced with high voltage circuits.
 
Re: Tinkering with Bias?

You're probably right, Texas. I guess I was answering the question from someone who feels comfortable doing it, but I wouldn't suggest having a running amp exposed on a bench, if you've got limited knowledge of it. Even an amp that's not plugged in can shock the living @#$% outta you. Keep your hands AWAY from those big filter capacitors....the big blue or gray things that look like plastic tubes. Those have lethal voltages stored in them. FYI Again, if you don't know what you're doing, pay someone $35 to bias it for you. If they charge much more than that, call someone else.
 
Re: Tinkering with Bias?

Gearjoneser said:
You're probably right, Texas. I guess I was answering the question from someone who feels comfortable doing it, but I wouldn't suggest having a running amp exposed on a bench, if you've got limited knowledge of it. Even an amp that's not plugged in can shock the living @#$% outta you. Keep your hands AWAY from those big filter capacitors....the big blue or gray things that look like plastic tubes. Those have lethal voltages stored in them. FYI Again, if you don't know what you're doing, pay someone $35 to bias it for you. If they charge much more than that, call someone else.
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NP, Gearjoneser. Just trying to look out for the kids. :)
 
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