From: Patent Tactics, George Brock-Nannestad
Hello,
from time to time this crops up on ARSCLIST (although I can only locate April
2004 at the moment), because it is highly relevant, both for recording and
reproduction done with synchronous motor drive and when using stroboscopes.
We are now so fortunate that we have a reasonable certainty of having either
50Hz or 60Hz (not to mention 400 Hz in aircraft), but that was very far from
the real world, say from the 1920s and until ca. 1965. I have a fairly good
impression of what went on in the US and in the UK (and in central
Copenhagen, Denmark, they had DC until 1962!).
Ca. 1980 a Danish record collector who had started late in academia, studying
the subject of contemporary history, decided to write his thesis for B.Sc. on
historians' problems in using sound recordings as historical sources. His
name was E. B. Mortensen, in the 1970s a frequent contributor to Talking
Machine Review, and his thesis was huge. It was a rambling discussion based
on a lot of misunderstood acoustics, but it impressed immensely his non-
technical history-based supervisors. He took innumerable measurements and
made innumerable calculations that were quite misleading, and he used his
ears. He purported that most of the 78s we listen to were really recorded at
75 rpm. He discovered that Hitler sounded much better if the speed of his
recordings were reduced by 10%; the speech became much less hysterical and
probably more threatening, cajoling, etc. Without any source he claimed that
the Germans had reduced their power line frequency from 1935-1944 to 47.3 Hz
to save power, and that consequently, when we reproduce at 78 rpm we get an
erroneous result.
I was given a copy of the thesis by someone who wanted an independent review.
I thought the conclusions on Germany were utter nonsense, but how do you
disprove such a statement? I worked my way through volumes of the foremost
German electrotechnical journal, Elektrotechnische Zeitschrift, the
publication of which petered out in 1944, due to shortages and the fact that
the pages were quickly filling up with obituaries and death notices. Nowhere
did I find anything that could prove or disprove his statement, and anyway,
all synchronous clocks would run slow. It was counter-intutitive to a
technician, because if heavy machinery needed more power at a lower speed it
would simply draw a higher current, and the real saving only occurred during
the actual run-down from 50 Hz to 40-something Hz, which could be termed a
one-time flywheel effect. I did find papers on the instability of frequency
and slow regulation of hydroelectric plants, but I also found the frequency-
stabilised converters used for film cameras. Apparently no problems in the
professional sector. As Allan Koenigsberg said a short while ago, "How does
one prove a negative?"
Now, 26 years later I am finding material that seems to indicate that there
may have been some truth to Mr. Mortensen's assumption: at least during 1944
they did lower the mains frequency to 45 Hz, and indeed it appears that
Germany towards the end of the war had been split into two sectors, one using
43 Hz and the other 41 Hz. There is a strange logic to why this would save
energy. You may skip the next if it is too detailed.
The frequency really only influenced operation of motors: all AC motors would
run more slowly. This meant that e.g. rolling mills, overhead cranes,
elevators, etc. would have a lower throughput and thereby a lower power
consumption. The voltage was maintained, so lights, heating, vacuum cleaners,
etc. would not be influenced. The only real problems would be in the iron
used as cores: it would be more likely to saturate and hence the efficiency
would fall and transformers would risk overheating. The heavy electrical
industry had already optimised the balance of copper and soft iron, and that
was for the specified frequency. By the way, house wiring was made with iron
wire and small transformers used zinc wire in the last days of the Reich.
Now, there are still a lot of open questions here: was any recording and
reproduction done at all at mains synchronous speed at that time? And what
was the timeframe: Hitler's speeches had been recorded from about 1932, and
surely they could not suffer from this phenomenon before the terrible
shortages set in. But I am certainly no longer cocksure. But, as I have said
on this list before, one of the German broadcasting houses had a quartz-
controlled power line installed for their tape recorders and gramophones in
the 1950s. Perhaps not to re-live life's complications.
I have also recently found via the website:
http://vwgc.org.au/VWGCGramNotes.htm
that Western Australia had 40 Hz until 1958, and they show a 40 Hz 78rpm
stroboscope.
The BBC was aware that there might be variations in the mains frequency, and
on:
http://www.btinternet.com/~roger.beckwith/bh/grams/grams_4.htm
you may find calibration discs and a stroboscope "For use when mains
frequency at the time of recording differs from that at reproduction". In
reality it was no more than 2 Hz either way, and the circles were marked in
difference frequency, rather than rpm. The central German broadcast archives
had actually informed Mr. Mortensen that the recordings of the German radio
stations were marked on the label with the mains frequency! But he obviously
did not believe them.
The story continues. I would not be surprised to learn that northern Italian
records were cut with machines run off 14 Hz or 16 2/3 Hz, which were in use
for traction purposes. Let us see if a type-wri-toon will work here: ;-) -
yes, it did.
Kind regards,
George
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