[Big Bad Bob]

On 02/02/11 19:44, Patrick Turner so witilly quipped:
Halcro managed to make SMPS for their 200W solid state class AB mosfet
monoblocs.

most likely it was for cost reduction

Many professional SS amp makers have embraced SMPS.

I wouldn't do anything else for a high current power supply.
Transformers are too cost prohibitive. I look at a lot of small
electronic devices (computer related) with 'wall warts' and 5 years ago,
most of them were heavy iron things that fell out of the socket
sometimes. Now they're almost ALL switching supplies, less than 1/3 the
previous size, and weigh practically nothing by comparison. And,
understandably, at a much lower cost per watt.

But making a SMPS capable of +450V at 1amp dc + seems rather too
difficult, and since a tube amp still needs an OPT, weight is high,
and so makers think they may as well include a PT which is the same
weight as the OPT.
May as well get hung for stealing a sheep as for a lamb.

heh, interesting analogy.

Still, a 450V switcher isn't all that difficult. Some of the simplest
switchers perform their regulation from the primary side of the high
frequency toroidal isolation transformer by measuring the rectified
output from the secondary, then use PWM or similar to alter the duty
cycle going into the toroid, with optoisolators and whatnot in the
feedback path to make sure you don't accidentally put 'mains' on the
ground plane. That being said, if the ~450VAC (at xxKhz) output goes
into a simple rectifier and a CLC or LC filter, it wouldn't be a whole
lot more complicated than a transformer [assuming the switcher on the
primary side is a well-known good design]. As I understand it, most
modern switchers use the method I described, particular in computer
supplies. There's a 1990-something US patent describing it all,
actually. I forget who did the patent. Ending point, everything up to
the toroid transformer is pretty much the same for ALL switchers, with
the obvious exception of the expected output voltage and the necessary
component value choices on the secondary side.