Charlie:

I don't think the MLS tests would necessairly be of any more use than a conventional distortion analyzer and ocilloscope (I''m assuming you are talking about electronic measurements here, not acoustic ones). If you zoom in enough at the crossover point of the wave on a solid state amp, you can sometimes see the 'glitch'. With high sensitivity speakers, it can be heard as a 'roughness' and 'courseness' to low level signals. In extreme cases, I have heard the sound actually dropping out as the wave transitioned the crossover point - it sounds a lot like a low bit rate digital recording, without dither added (sort of like telephones can sound if the sound was digitized at some point). Since on a tube amp each half of the push-pull stage is essentially operating class "A" for a significant amount of it's power range, there is no crossover notch to be generated. By the time it does cross into class "A/B", any crossover glitch is a small proportion of the total signal level. A solid state amp generally is designed to have very little overlap of the positive and negative swings of the wave. Of course a solid state amp can be constructed that has a richer biasing, even pure class "A". This is almost never done however except for very high-end (and expensive) amps due to the costs and amount of heat generated. This heat becomes even more of an issue in a multi-channel amp intended for home theater.

[This message has been edited by soundhound (edited January 20, 2003).]