The Alchemist tube bias settings have not been released to the public, due to the complexity of multiple parameters in the biasing. Please contact Line 6 UK for an authorized Line 6 service center in your region:
Line 6, Inc.
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Telefon: +44 (0) 1327 302 700
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I think mine is a bit low set. How hi/hot can i go?
Tubes are tube and setting the bias is necessary for them to run within their proper perimeters. All tube amps have bias resistors (afaik). An amp with a preset bias will have a bias resistor of the proper value to bias a tube of known parimeters. If you replace the tubes then you will need a new set of tubes that matches the parimeters of the old set. Other amps will also have a bias resistor but the resistor will be of a lesser value than the amount needed and a variable resistor is added so a wide range of tubes might be used. If one were to buy a set of tubes that will not bias within proper tube specifications then the variable bias resistor isn't large enough to adjust to the resistance needed so a new set value resistor is selected and installed so the amp can be biased. The difference in the resistance values on these set value resistors can be easily calculated but most people usually just tries different value resistors until one can be found that will allow the amp to be biased. This is all simple stuff here.
Many tube vendors will ship their tubes with the max tube dissipation (in watts) printed on the box cover. You would then simply measure the plate voltage of the amp and apply a simple formula to this voltage using the printed data on the tube box and come up with the recommended bias setting for this set of tubes. If the tube vender does not supply this required number (in watts) for a set of tubes then someone would use the numbers on the tube datasheet for that particular brand of tubes and do their calculating (again using the formula) to establish the proper bias adjustment. Again, this is simple stuff also.
If you don't already know all this "simple stuff" then I can only recommend you take your amp in and have it retubes/rebiased/etc by a true amp tech professional. Working on tube amps is/can be very dangerous because of the super high voltage one will find inside them. Its not worth taking risks for a couple of bucks!!!!! Be safe man.
It's been a couple of days since we've heard from you. We're going to assume your question has been answered and close this thread. If you still have questions please feel free to open a new question with us and we will answer your questions accordingly. Thanks!
sorry for bumping the topic up, but Im about to buy the Alchemist amp, and Im from Belgrade, Serbia. What should I do when the tubes need replacing? I seriously dont think that I could wait and cover the expences of sending it to america/japan/any other country for servicing.. I need to know how to set it up by myself..
btw I have a spider 3 120 for practicing, so Im a loyal customer hehe..