What the heck is bias anyway?

Kirkus, where the analogy of idle speed falls apart is with an engine, regardless of whether I set the idle speed at 500 (for the sake of example - too low), 800 (recommended), or 1650 (too high) RPM, performance will be identical at 2500, 3500, or 6000 RPM.

With a tube amplifier biased at 20 mA (again, for the sake of example - too low), 50 mA (recommended), or 75 mA (too high), its performance will be different in readily apparent ways when playing music.

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How often to you have to set and check the bias on a tube amp?
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My injectors are class D but I only run them in class A. I generally bias with IAC adjustments but sometimes fuel pressure.

Mitch4t, this depends on the amp. Some amplifiers have very stable bias settings and can be checked maybe once every 6 months. Others seem to need constant observation. So I would go with the manufacturer's recommendations.

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Thanks for the reply Atmasphere. I really would like to try tube amps, but I'm not mechanically inclined at all. I'm a plug and play kind of guy, which is why I have solid state amps. I'd consider tube amps as long as they don't require much fiddling around with. I think I read somewhere on Audiogon about self-biasing amps. If that technology exists, why don't all tube mfgs use it. Is self-biasing expensive to implement? Is it as accurate as a manually biased amp?
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