As originally configured, the amplifier was constructed on two chassis,
the power supply on one chassis, and the audio circuit on the other.
The recommended capacitors were huge oil filled, expensive units with
low capacitance. No chassis for the amplifier was available, and had
to be cobbled together by the constructor. It was all amateur stuff.
At the time, the entire industry was amateur stuff. Even so, the
quality of the new component audio was so superior to "set"
manufacturers like RCA, Philco and Zenith that the Hi Fi buffs lived in
the clouds, so to speak. Their gear was a quantum leap ahead of set
manufacturers.


So far so good, except back then everyone had basic sheetmetal skills,
or at least enough sense to find someone with shears and a metal brake.
Bending up a chassis was seen, rightly, as easy and simple. Moderns
apparently have lost this knowledge.


In 1950, Hi Fi bugs didn't know what "feedback" was. Any old theory of
feedback was an improvement over nothing. Williamson had phase
diagrams and curves to show that in order to place a stable feedback
loop around an amplifier, the problem was phase margins. In order to
assure stability, the output transformer should have a response from 2
to 200,000 Hz. This assured that the amplifier was stable in the audio
range of 20 to 20,000 Hz. This criteria had merit. Unfortunately,
Williamson did not carry his analysis far enough. Seemingly, he never
actually built a model of his amplifier. If he had, he would have
realized that there was more to it than an output transformer and
feedback loop. The only component in his design that met the 2-200,000
Hz. criteria was the output transformer. As presented, the Williamson
amplifier had a number of serious flaws. It was a good start, but it
was not thought out properly. When the author built a Williamson with
the Partridge transformer, he soon discovered these flaws. The
Williamson circuit and a critique will now be discussed.


Williamson built _several_ prototypes of his amplifier and understood
its practical limits quite well. This is writing by an Old Guy who
didn't RTFM back then and hasn't since. Stan is like the old uncle who
loudly insists P-38 Mustangs were built by Vortiskorky and American
mores were perverted when "that J** ******* Henry Miller" corrupted
literature with that book they made into a movie where the guy openly
grabs Jayne Mansfield's ass while playing Ping Pong.

We will discuss the circuit, block by block.

The Power Supply:

The Williamson power supply was built on a separate chassis. It had a
high voltage cord that connected it to the audio amplifier. Such
configurations aren't built any more. They are dangerous. Running a
400-volt DC power line for domestic use is against UL standards. The
seeming purpose of this set up was to isolate the power transformer
from the audio circuit (and output transformer). It has been shown
that there is no purpose in such a setup.

Many commercial amplifiers were built this way including several
McIntoshes, the Gotham Audio cutting head amp, and others plus several
Amateur Radio sets ("Amateur" means "used in homes") and who knows what
else. It was particularly in vogue among homebuilt projects because it
DID offer huge advantages in noise as well as being able to power
multiple widgets with the one supply. If you wanted to build another
amp and reuse the power supply you could. Or you could use it with any
homebuilt whatever. I believe this is STILL good practice even todayand
encourage it. When Ed Dell built his "Super Dynaco" amp and wrote it up
in Stereopile in 1967 or thereabouts he did exactly this.