Mr G- You may want to realign your blanket statement, re:
MOS-FETs
and
current. MOS-FETs are innately self-protecting, regarding
thermal
runaway, unlike bi-polar transistors
(http://www.onsemi.com/pub_link/Collateral/AND8199-D.PDF).
I sold(mostly modded)
David
Hafler products, for years, which all used MOS-FETs as
output
devices. As a sales point: I used to demo the DH-500,
measuring the amperage into a 2 ohm dummy load. I had read
as
high as 48 amps, without damage or overheating(and thermal
protection activation). You could practically arc weld with
the suckers! I, as well as a couple other customers, owned
Acoustat Model III's, and had excellent results with the
Hafler amps, at realistic SPLs.