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VINTAGE RADIO
By JOHN HILL
A look at early radiograms
The first recorded words were: “Mary had a
little lamb”. Of course the voice that made
that historic recording was that of Thomas
Edison and the year was 1877.
Edison’s record was cylindrical and
the surface was covered with foil. The
device was crude and it had a lot of
development work ahead of it before
it could be of any commercial signifi
cance. The late 19th century saw the
birth of many new gadgets and inventions, the phonograph being just one
of them.
If one listens to an Edison cylindrical phonograph, the first impression
is how terrible it sounds. Any subse-
quent impressions simply reinforce
the first. The reproduction is thin,
harsh, scratchy, totally lacking in
bass and distorted at particular frequencies. When I demonstrated my
Edison machine to my brother, his
comment was: “I had no idea they
were that bad!”
Looking at the recording industry at
the turn of the century, it could only
go one way – forwards!
It’s all very fine to look back in the
light of today’s knowledge and comment on how bad early records and
record players were – but everything
has to start somewhere. Most inventions undergo development and
modification for the rest of their com
mercial life. Whenever we look back
at early sound recording, radio, motor
cars or whatever, it doesn’t pay to be
too critical because that was the best
mankind could do at the time.
New developments
Most inventions start out with humble beginnings and improve as time
progresses. The phonograph was like
that and it went through many changes
– from cylinder to disc, vertical “hill
and dale” modulation to lateral, from
huge sound horns to built in types
with volume controls. But the real improvements did not come about until
records were electrically recorded and
could be played electrically through a
radio receiver. This new era of sound
recording and reproduction came in
around the late 1920s.
Electrically made recordings greatly improved the quality of recorded
sound and electronic sound techniques opened up a whole new frontier with the advent of talking motion
pictures. So, from this time on, records
and radio merged closer together.
Anyone with an ear for quality
would prefer to listen to their records
played through their radio rather than
a phonograph. Indeed, most radio receivers from the late 1920s to the end
of the valve era had some provision
built into them to allow a pickup to
be connected.
Early pickups
A genuine four-minute Edison cylindrical record. These early records were
“hill and dale” types; ie, the modulation of the groove was up and down, not
sideways as in later years.
88 Silicon Chip
Early pickups were big and heavy.
They used a large magnet and were fitted with a thumbscrew for holding the
“single furrow record plough” with
some of the lightweight pickups of
the microgroove era, the difference is
amazing. So too is the difference in
record life.
Playing records
This old magnetic pickup was made by the American Bosch Company. With its
6-ounce (170 gram) head, steel needle and lack of counterbalancing, it no doubt
wrought considerable damage on many an old record.
This close-up view shows the Bosch “Recreator” with its cover removed. Note
the horseshoe magnet, the pole pieces and the 2kΩ coil between the pole pieces.
The thumbscrew at the bottom is for securing the needle.
steel needle which needed replacing
after every playing.
As can be seen from one of the
accompanying photographs, the
pickup head contains quite a sizable
horse
shoe magnet, with a 2kΩ coil
mounted between the pole pieces. The
armature that vibrates inside the coil
is rubber mounted and it is the agehardening of this rubber mount that
causes trouble with these ancient
pickups.
If the needle carrier and armature
are remounted in soft new rubber, it
will restore the pickup to working
order once again. Assuming that the
coil is not open and the magnet has
not lost its magnetism, the pickup
should work.
Some of these old pickups weigh
in at around 6 ounces (170 grams)
and many had no counterbalancing
to lighten the load. Transfer all that
weight onto the tiny contact area of
the needle point and you have an instrument that has been scientifically
designed to tear the guts out of the
needle track of a record in a relatively
short period of time (or record time
if you will excuse the pun)! In this
respect, they were no better than the
acoustic sound heads they replaced
–and in some cases worse.
When ones compares the Bosch
Now if one wishes to play 78rpm
records through their old 1930 TRF
receiver, it’s not just a simple matter of
plugging in a pickup and away you go.
If you do this it will work, no doubt,
but the volume control on the set will
not control the volume of the records
being played.
The reason for this is quite simple.
In the late 1920s and early ’30s, the
volume control on nearly every type
of receiver was in the radio frequency
(RF) end of the set, which was contrary
to later developments. In those days,
the volume control took the form of
a wirewound potentiometer which
either varied the cathode bias or the
screen voltage of one of the RF valves.
In operation, the audio frequencies
produced by the record pickup are fed
into the audio section of the receiver.
In an old TRF or early superhet receiver, the grid of the detector valve
or first audio valve was the place to
attach a pickup.
But as already explained, any audio
grid comes after the receiver’s volume
control and so the record volume is
uncontrollable in such circumstances.
In most cases, the sound would be
too loud and possibly distorted if the
pickup output is too great for the set
to handle.
For this reason, the pickups of old
came with an external volume control.
Although these units were nothing
more than a potentiometer, with perhaps a capacitor across it, they were
often given names to suggest otherwise. The “ELEC-TRU-TONE” was one
such example – see photo.
The pickup connections to radio
receivers varied depending on the
manufacturer. Some used terminals
while others used sock
e ts. Some
disconnected the radio section using
a switch while others did not bother.
With the latter arrangement, the set’s
volume control needed to be turned
down to prevent radio signals from
coming through and interfering with
the pickup signal.
Early radiograms
The first radiograms made an appearance during the late 1920s and
May 1996 89
Early pickups required a
separate volume control
because the radios of the
day had their volume
controls in the RF section
of the receiver, not in the
audio stage where it was
needed. The unit shown
here was made by Bosch.
these had a few variations too. Some
had clockwork turntable motors while
some were electric, or sometimes an
electric motor was an optional extra.
These old radiograms still had the
same volume control arrangements as
before, with the pickup having its own
external volume control. This control
was usually mounted somewhere near
the turntable. There was also an on/off
switch and a speed controller.
It would appear that the radiogram
idea wasn’t all that popular at the time,
as anyone who could afford to buy a
radio would most likely already have
a phonograph. A radio with a pickup
was a much cheaper record playing
option if you already had a turntable.
However, a complete radio/record
player in one would be far more convenient to operate.
A few headaches
Any collector who finds an early
radiogram with a lift-up lid has a
really collectable item. If it is in poor
condition, however, he may have
found himself a few headaches as well,
because items such as early turntable
motors, pickups and volume controls
Above: this side view of the Bosch volume control clearly
shows the sockets for the pickup connectors.
Right: this “ELEC-TRU-TONE” volume control is similar
to the Bosch unit but the case is made of bakelite (the
Bosch control’s case is pressed steel). Note the four socket
connections.
90 Silicon Chip
can be difficult to locate and repair.
So far, we have described how
records were played through a radio
receiver. But strange as it may seem,
there was a time when the opposite
was true and some radios were played
through a phonograph!
Back in the days when many radio
receivers came only with headphones,
there were problems as far as family
listening was concerned. Enter the
phonograph to the rescue!
It was found that if a phonograph
needle was placed on the earphone
diaphragm, the earphone would
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Shown here is the rear of an old AWA Duo Forte radiogram. The pickup plugs
into the righthand sockets, while an extension loudspeaker can be plugged into
the lefthand sockets.
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Silicon Chip Binders
The Duo Forte’s turntable and pickup are crude by today’s standards. To the
right of the pickup arm is the turntable’s on/off switch and speed controller.
Once again, note the extremely heavy pickup and the lack of counterbalancing
at the far end of the arm.
activate the diaphragm in the phonograph’s sound head. As a result,
the phonograph’s sound horn would
reproduce the radio program for all
to hear. One can only guess at the
volume level and sound fidelity of
such an arrangement.
Of course, this would only work on
an Edison type sound head, meant for
vertical (hill and dale) recordings. If
the sound head was of the lateral type,
a special adapter could be bought (this
adapter was originally intended to
convert a lateral type machine to play
Edison vertical cut records).
The invention of the phonograph
preceded the first practi
cal radio
demonstration by 11 years. Although
they both evolved separately for quite
some time, the two eventually became
inter
woven. Radio technology was
used to improve recording techniques
and the improved recordings could
only be heard at their best when played
through a radio receiver.
It was therefore only logical that
the record playing radiogram would
evolve to become the centre of household entertainment and it remained
that way for many years until the
advent of television, modular sound
SC
systems and the compact disc.
These beautifully-made binders
will protect your copies of SILICON
CHIP. They are made from a dis
tinctive 2-tone green vinyl & will
look great on your bookshelf.
Price: $A11.95 plus $3 p&p each
(NZ $6 p&p). Send your order to:
Silicon Chip Publications
PO Box 139
Collaroy Beach 2097
Or fax (02) 9979 6503; or ring (02)
9979 5644 & quote your credit
card number.
May 1996 91
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