I see some of the amplifiers have no mica or silicon sheets between the transistor and the output heatsink. What topology is it?
Regarding output devices capacity is it better or worse to isolate the HS from the output devices?
Like here: http://www.diyaudio.com/forums/vend...e-mosfet-amplifier-module-47.html#post4582999
what are the pros of using such direct mounting? one advantage is heat can be transferred faster. But how about if heatsinks are used on the sides of the amplifiers and the amp is running at above +80V so even the DC at that voltage will give some sort of shock.
In the configuration shown above heatsinks are grounded, literally, so sit at 0V .
Conventional (common collector) amplifier means, that the rails are running on the heatsink.
QSC solution with the grounded heatsink looks very elegant, but sometime I feel, that they sacrifice too much from the sound quality to be able to do it.
Crest use live heatsink in the ProX200 series, but it's connected to the output, which is another possibility using common emitter output stage.
Can you kindly elaborate about the sacrifices in sound quality ?
Well, the last thing I would call a typical QSC power amp is "simple". What with multiple power rails commutating, and separate little cards to control that, simple is the last thing I'd call them.
You can make the case for direct contact to a heat sink as "better" heat transfer than through a mica or silicone insulator, but really, either method can easily be designed for proper heat removal, so it really is more a matter of how you want to do it, rather than heat. Either way works just fine.
but to blame the topology is to assume nothing else about the amps was different.