Many people actually refer to them as 'self-biasing' for this reason. Here are few of the more popular types found in tube amps:Ĭathode bias amps are the least work intensive, as they do not really require biasing at all in a general sense. There are a few different ways that the bias is set on an amplifier and some are more involved than others, though it is hard to say that one is really better than the next. For this reason, when changing power tubes in a tube amp it may be necessary to set the bias on the amp to make sure it is optimized for the new set of tubes and not the set you just replaced. Unfortunately, that is one of the realities of vacuum tube production and honestly it has been since the beginning.

Even within a single brand of tubes you will find one set that may vary wildly from the next in terms of it's operating characteristics. The reason for this is that each set of tubes is going to have different performance characteristics that will affect how the bias should be set. Think of it as an acceptable range, not one single point. It's more akin to a moving target than an exact point. So if there is an optimum setting, why not just set the bias to that point and leave it? That would definitely make the most sense, but the problem is it's not really that simple. Too much and the life of a tube is significantly decreased and in extreme cases failure can occur this is also referred to as 'biased hot.' Too little and unpleasant distortion (crossover distortion) is produced this is referred to as 'biased cold.' The correct setting is crucial for an amp to perform at its best both functionally and soundwise. The purpose of setting the bias of an amp is to find the optimum setting for the flow of current when the amp is idling.

When it comes to tube amps the idea is basically the same, however, instead of fuel and air we are dealing with electrical current. The idea is to find the perfect balance for optimum performance. The fuel and air mixture is adjusted so that the motor runs smoothly too much of either and the motor won't run very well or even possibly not at all. Nowadays most cars have complex computers that control the idle, however, in the end the process is still basically the same as it has always been. The best way to understand bias is to think of it like the idle setting on a car. FINANCING Blowouts Gift Certificates Testimonials Reviews & Articlesīefore we talk about different types of biasing found in tube amps, it is probably a good idea to explain what exactly the bias is.

Fixed bias guitar amp