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ARSCLIST  November 2009

ARSCLIST November 2009

Subject:

power line frequency

From:

George Brock-Nannestad <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Wed, 4 Nov 2009 01:09:57 +0100

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (103 lines)

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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