Dual Bias Adjustment

It is pretty much accepted that today's tubes are getting better all the time in terms of performance and sound. However, tube manufacturers still have not been able to match the quality or consistency of tubes built 40 to 50 years ago. There was a time when you could buy pretty much any EL34 and just plug it in with the assurance that your guitar amp would play and sound as good as ever. These days are different. You really need to watch what goes into your favorite amplifier as far as output tubes are concerned. There seems to be an incredibly wide range of electrical characteristics among any given type of tube. This fact has fostered the "matched pair" tube market, where the distributor tries to take the worry out of getting the right specification output tube into your amplifier. However, even with matched pairs and tube grading systems, sometimes you just "can't get there from here" when it comes to your favorite type of output tube. Most tube amp users agree that having adjustable bias available for the output tubes of their amplifier is a worthwhile feature. In fact, adding an adjustable bias control is one of the most common modifications undertaken in our repair shop.

DST's amplifiers that use "fixed bias" (as opposed to cathode biased output) all incorporate DUAL BIAS adjustments. This gives you the ability to individually adjust the bias of each output tube and better match the individual performance of the tubes available. This also takes away the necessity of buying matched pair or specifically graded tubes. Total control and flexibility of the output section of your amp is maintained regardless of the type or brand of tube you choose.

Have a question or want more details? Contact Bob Dettorre, VP Engineering, DST Engineering
bob@dst-engineering.com

DST Engineering Dual Bias adjustment - Copyright (c) 2002