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It is ridicules how pleasant the Yamaha B2 sound when it operates in class A and how much worse it sounds when it switches to class AB. I did not measure the power but with default 40mA it switches to class B very soon. With my current cooling techniques I can run the amp at 120mA where it plays in class A up to the volumes (or a bit less) where I typically listen.  I would like to keep the amp further without switching into class AB but it does not dissipate heat good enough with my cooling. What would be very good is to have a pure class A biased amp on the V-FETs.

I will probably try a different cooling, trying to bias the B2 at 150mA. A bit dangers as it looks like B2 has no thermo-protection. Also one of B2 channels is switching to class AB at 8dB sooner than the second channel driven with the same current. It needed to be adjusted but I do not have too much knowledge about SS. So, I guess I need to find a local technical who would calibrate both of channels to enter class AB at the same time. It shall be very simple to do. Probably to throw in there a thermo-relay would be a good idea, if I intend to drive it too hot. Perhaps I would need to put in there a switch that would drop bias to 50mA, switching it to summer mode….

It is not too hard to do myself but I would like not to. It would be cool to have a local guy around Boston who is accustom with SS amp and who would be motivated to work on my Yamaha B2.

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