"~misfit~" wrote in message
...
Somewhere on teh intarwebs Arny Krueger wrote:
[snip]
As time marched on, fairly inexpensive and modest-sized output
devices with excellent SOA and reasonble high frequency resposnse
made it relatively inexpensive to build very high powered audio power
amplifiers.

Arny, would you care to give a rough time-frame on this? I have a few old
SS amps (and might grab a few more if I see them at bargain prices) but
would love to know roughly when, in your opinion, SS amps became stable
and fairly clean across the frequency scale. Thanks.

Late 60s-early 70s.

Most of the money ended up in the heat sinks, power
supply transformers and filter capacitors. The former are continuing
to shrink as improved output devices improve their reliabiity at
higher operating temperatures and power supplies are making greater
use of switchmode technology.

I've always wondered why amplifiers never (at least AFAIK) embraced the
use of heat-pipe technology to move the heat to side or back of case
passive radiators.

Easy enough to put the devices and the heat sinks where you want them. Heat
sinks often end up on the backs or sides of amp cases, so no need to move
the heat around.

I've actually used a heatpipe cooler from a laptop for just this purpose
(although it needs a fan on the radiator, as that's how it was designed,
the fin area isn't big enough to passive) when I re-housed a basic
subwoofer amp from a nasty plastic housing (previously mounted on the
front of the driver's box, with connections on the back) into a re-used
bookshelf speaker box.

Heatpipes are amazing things. I've a small collection of coolers from
laptops that I've put together to illustrate the impact heatpipes have had
on cooling and removing heat. They all use small fans and go from a
(relatively) massively-finned aluminium plate (when CPUs only had about
20W of heat to shed) to a slightly smaller ali plate incorporating a ~4mm
heatpipe in a groove. Then, as CPUs got very hot (at least Intel ones) I
have a heat-remover (I don't know a more accurate name for this one
really) that's got an ali 'girder' and *three* 4mm heatpipes ending with
two fans and radiators (I'm guessing for redundancy) and a third, separate
fan blowing out the side, from the time when Pentium 4s were wasting near
100W of heat. The next cooler, from merely 18 months later, still moving
the same amount of heat is a single 8mm heat-pipe 5cm long, no ali casting
at all between the heat source and the single variable-speed fan blown
copper radiator.

Laptops and PCs are specialized enough, low-powered and costly enough that
when there is a technical problem to solve, the money is there to use a
relatively expensive solution. Not so with power amps. Lots of heat to move
and less costly solutions work well enough.