The Williamson valve amplifier.
We have complete set of parts to make a pair of Williamson valve amplifiers.
Shown above is a pair of Williamson output transformers and a pair of Williamson mains transformers.
and many other items. These Williamson parts have been in the collection since 1992.
Partridge output transformers built to Williamson specifications (also see advert below).
RS components (used to be called Radiospares) mains transformers built to Williamson specifications.
GEC KT66 valves including matched pairs. Oil filled capacitors and chokes.
No museum would be complete without the Williamson amplifier. The Williamson papers were
printed in 1947 and it is the most famous and important valve amplifier design of all time.
It used the new GEC KT66 triode valve (tube) that was developed by GEC just before WW2
The valve was restricted to military uses during the war but was absolutely ideal for
audio use. Williamson worked for GEC and after the war he printed his valve amplifier
designs in Wireless World magazine. In those days, buying a complete piece of consumer
electronics in the shops was not the only option. Many designs were printed, or in kit
form. The Williamson design was so popular that many manufacturers built transformers
to Williamsons specifications and audio enthusiasts built the amplifier from parts.
D. T. N. Williamson wrote,
"It appears then that the design of an amplifier for sound reproduction to give the highest
possible fidelity should centre round a push-pull triode output stage and should incorporate
negative feedback. The most suitable types of valve for this service are the PX25 and the KT66.
Of these the KT66 is to be preferred since it is a more modern indirectly heated type with
6.3 volt heater, and will simplify the heater supply problem. Triode-connected it has
characteristics almost identical with those of the PX25."
Update Feb. 2008. The original "Wireless World" magazines. April and May 1947.
As shown at the top of this section, reprints are still available of the
Williamson amplifier "Wireless World" publications.
Now, in the museum, we have the two original magazines showing both parts 1 and 2 of the original
Williamson articles and these detailed the full designs of the Williamson valve amplifier.
See an interesting article at http://www.tcaas.btinternet.co.uk/jlh1996.pdf
Bert van der Kerk shows how to build a Williamson amp at http://www.xs4all.nl/~ideas/amps/index.html
Some companies did build Williamson amplifiers to Williamson specifications and these are shown below.
It was certainly one of the more expensive amplifiers available at the time mainly due to the large
number of high quality components that were needed to build it.
£31 From "Rogers" is approx. $62 and in 1952 that was expensive - In 1952 in the UK the weekly
wage for the working man was about £5 per week and so £31 was 6 weeks pay! Also remember that
this was for a mono amplifier. Two Williamson amps would be required for stereo. No wonder many
people opted to build it themselves and that assumes they could afford the parts. It is interesting
that Rogers Developments Co. who made valve amps and transistor amps for many years are,
in 1952 selling fully assembled Williamson amplifiers. (Adverts from "Wireless World" 1952)
A pair of Quad II power amplifiers
(introduced 1953) and 22 pre-amp
control unit (introduced1958).
These units are in mint condition and complete with manual.
Quad advert from Hi Fi News magazine 1958 including the Quad II amps and 22 valve pre amp.
Also in the advert is the Quad valve tuner unit and Quad electrostatic speakers.
The Quad II power amps were sold for 18 years. In 1958 the Quad FM tuner was also introduced.
These Quad valve amps have been in the collection since 1990.
Update. A big effort was made in Jan. 2010 to fully service the Thorens TD 124 turntable and
use it with the Quad amps, Here are some new pictures of the amps now in use.
They are driving a pair of JBL speakers.
The valves are original GEC KT66s. Two matched pairs of KT66s with very low hours.
A very interesting site which includes notes and pictures about restoring Quad valve amps can be found at
In particular, how to upgrade the old resistors and capacitors to protect those valuable KT66s.
Trio WX-400 valve (tube) receiver
(tuner amplifier.) 1962
Little is known about this very interesting unit.
It is likely to have been built between 1960 and 1962.
Kasuga Radio Co., Ltd was established in 1946 and renamed Kasuga Radio Industry Corporation in 1950
and then again renamed in 1960 - Trio Electronics, Inc.
In 1962 Trio introduces the first transistor products and by 1966 all products are fully transistorised.
This Trio WX-400 receiver was also known as the Kenwood KW-70.
Trio eventually became known as Kenwood Corporation. (Kenwood Electronics in the UK).
In the States Trio has always been known as Kenwood and it is likely that the Kenwood KW70 was the
US version of the Trio WX-400. There was also a WX-500 although not sure what the differences were.
The WX-400 has 22 valves and is an AM/FM Wide Band Stereo Receiver
The appearance, with it's chrome edging is typical of early Japanese domestic Hi Fi and consumer electronics.
It has been in the collection since the early 1980s and was bought from a friend. There is almost
no information about this unit on the internet and as usual manufacturers web site are of no help.
Any information would be most welcome.