#1
Someone i waz just talking to kind of raised this question. Carvin X100B's come in 2 versions. one that uses EL34's and one that uses 6L6's.

Can I buy one that uses EL34's and modify it to run on 6L6's?

Also what does it mean to bias your amp and how is it done?
#2
Its not that easy of a change but its possible... and costly.

Biasing refers to the power stages of the tubes and how hard each stage is pushed to create your gain. It's generally not necessary unless something is wrong with your tone.
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#4
Depends on the amp. Some amps are switchable to run on either, like my Mesa Lonestar. On other amps, you replace some resistors and adjust the bias and you're all set. If you're handy with a soldering iron, you could do it yourself for the cost of the new resistors. If not, then you'll have to pay a tech to do it for you.

Bias refers to the operating point of the power tubes. It is usually a compromise between useable range and tube life. By range, I mean how much gain the tube generates before breaking into distortion. Amps use either fixed bias, or manual bias. An amp using fixed bias is easier to maintain, since you just replace the tubes and that's it. An amp using manual bias must be adjusted to provide the correct bias.

To set the bias, you need a digital voltmeter, a small screwdriver and test jig. The test jig mounts between a power tube and the socket. You use the voltmeter to measure the bias voltage. A small screwdriver is used to set the bias on a potentiomenter.

Bias should be checked each time the power tubes are replaced. It should be checked again a few months later, since it will drift. Remember, it effects your tube life, not just your tone.
Last edited by KG6_Steven at Jan 3, 2009,
#5
Quote by KG6_Steven

Bias refers to the operating point of the power tubes. It is usually a compromise between useable range and tube life. By range, I mean how much gain the tube generates before breaking into distortion. Amps use either fixed bias, or manual bias. An amp using fixed bias is easier to maintain, since you just replace the tubes and that's it. An amp using manual bias must be adjusted to provide the correct bias.


Fixed biasing actually needs rebiasing. Cathode bias amps are the swap and go types.
#6
Quote by Whole Lotta Led
Fixed biasing actually needs rebiasing. Cathode bias amps are the swap and go types.



Agreed.

The most common types of bias I know of are fixed bias non adjustable (means it just uses resistors) fixed bias adjustable (resistors and potentiometers working together, basically the same as the previous), and cathode bias which uses a cathode resistor. Only cathode bias doesn't need to be adusted.
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#7
We need to know which amp you have before we can tell you if it's a feasible swap.
One of three scenarios could occur:
-Your amp might be able to switch with just a bias change, like the JSX, etc
-It might need a few new resistors in the power section
-It might not be able to handle the current draw, in which case it wouldn't make sense to mod it for 6l6s.

Why do you want to change in the first place? If you've got a Windsor and you want to make it sound like a dual recto and you figure the 6l6s will do that because that's what the rectifier uses, you're wasting your time and money. In fact, in almost any case you'd want to mod your EL34 amp to 6l6s is a waste of time and money.