mag amp audio

[svetengr at earthlink.net]

At 05:03 PM 10/8/97 CST6CDT, you wrote:
>Carver at one point made an audio hifi amp 
>that was a mag amp based item.  I believe the one I read about was 
>about 8x8x6 inches or so and delivered a couple hundred watts.  I 
>suspect it weighed a lot, but was very effiecient and physically 
>small per power compared to the tube amps available at that time.  I 
>think this was circa about 1955 or 1960 or thereabouts.
>Can anyone elaborate on this?

1955 or 1960???? You poor kid.....

It was called the M-200 "Magnetic Field Power Amplifier".
There was no "magnetic amplification"--it was simply
a conventional solid-state amp with an early switching
power supply, which idled at a low DC voltage. When an
audio peak entered the amp's input jack, the power supply
automatically switched the voltage to the full value until
the peak ended. This Rube Goldberg thing was introduced
in 1973.

I know more about this than I want to, having repaired many
M-200s over the years (and having discarded even more, after
finding that repairing them would be far more expensive than
buying a new amp). Service technicians consider this product
one of the great atrocities of the consumer-electronics industry.
Many thousands were sold, and nearly all of them are in the
trash at this time.

They WOULD NOT TOLERATE overheating, overvoltage, overcurrent,
excessive input signals, speaker-coil damage, power-line sags
or spikes, and virtually any other kind of transient fault
condition. The M-200's extensive protection circuitry was not
very effective. Some people seriously feel that Carver deliberately
sold this amplifier to insure future sales of amplifiers, by making
his customers buy replacements for blown M-200s.

When an M-200 went, EVERYTHING went. I have seen units in which
every semiconductor device was bad--even the rectifier diodes. 

Regrettably, I have seen the "solid-state revolution" from the
ass end--the service bench. And one thing that I will cheerfully
argue with ANY smartass design genius (such as Mr. Carver), is
my honest opinion that a well-designed tube amplifier is MORE
RELIABLE than ANY conventional solid-state amp. And, is less
likely to destroy the speaker, thanks to the output transformer.