Dr Bunsen Honeydew wrote:OK I will bite, but you will be better off getting a reply from Colin he has far more experience of power fets than I have. By the look of it and the fact that this was designed for pro work means it is almost certainly a Hitachi application note product. There are many of them with similar character including Dave's HH one, only varying because of power supply design. Advantage, virtually indestructible, and powerful as if you over drive them they shut themselves down. The opposite to a bipolar amp which runs away (thermal runaway) if overdriven. Problems, high "on" resistance which means low level musical details at low volumes are lost and they sound different at different volume levels. Also bass is like from a different amp as phase is buggered by the early pos and the neg devices having different characteristics.
Much of this has been solved since those early days and FETs for hi-fi are now a better proposition as Colin will tell you. But I still see no advantage to change to using them.
Me I have no knowledge of FET,s never heard of them.
The MF300 was a bodged up version by Tony of the MF250, because the original FET,s became obsolete, and he could not work out the drive correctly, so he closed down the bandwidth and rise time etc. and screwed it up.
The MF250 was 20.2W P-P A Class at 240VAC in no voltage regs, the MF300 was only 12W as Tony pushed the bias up parasitic oscillations burst into life and bye bye tweeter and FET,s.
Have you ever seen a Parrot Sick it dreadful seed everywhere.
poor long suffering husband, I am an
and my wife
