Found Collection

Just back from the pub after one of THOSE conversations. Can anyone
help with this one?

Why was the first record speed 78rpm. Why did this then become 33rpm
for LPs and 45rpm for singles? Is there any significance in the
relationship:

               33 + 45 = 78

Just asking!

Steve

RCA Victor countered early the following year with the 45rpm record.  Both
were intended to replace the conventional "78".  RCA brought out
symphonies on 45rpm, and sold "albums" in boxed sets.
But the problem was that the playing time of the "45"
was still only in the 4-5 minute range, and breaks were still necessary,
even within movements of a symphony.  

For extended selections, the public preferred the uninterrupted 33rpm,
but the 45rpm was perfect for singles.  Due to generous cross-licensing
agreements, both Victor and Columbia (as well as numerous other smaller
companies) were each producing both speeds by the early 1950s.  

Hope this helps.

Mike Sherman

In article

Peter
Peter Bertini  K1ZJH
Senior Technical Editor,  Communications Quarterly Magazine
"The Radio Connection,"  Popular Communications Magazine
  --  proud members of the CQ family --

"                                                                              
It seems strange to me that the turntable speeds weren't harmonically          
related to the AC line frequency -- permitting the use of synchronous          
motors..  How were those odd speeds selected? "

---------

Interesting question.  I wonder if the answer is that at the time
RCA and Columbia were drawing up plans for the 45 and the LP, the
*** form of the phonograph was the "rim drive" or "puck
drive" design, which would have made it possible to pick almost
any turntable speed you wanted, using an ordinary cheapo motor
running at, way, 1250 rpm.  

A related question is that of tape recorder speeds.  The 30 ips
of the immediate postwar American recorders was derived from the
speed of the prewar German magnetophon, and subsequent speeds
of 15 ips and 7.5 ips for reel-reel recorders must have reflected
that earlier decision, recognizing the need for easy compatibility.

But even non-reel to reel tape recorders invented later still
apparently derived their tape speeds from that original 30
ips -- e.g. the modern cassette runs at 1 7/8 ips
(half of 3 3/4, which is half of 7 1/2, which is half of 15,
which is half of 30).  The Elcaset of the '70s ran
at 3 3/4, as did the 8-track.  The big RCA cartridge of the 50s
(discussed often in this ng) also ran at 3 3/4, and the abortive
3M/Revere cartridge system of the late '50s/early '60s ran at
1 7/8.  None of the tapes used on theese systems could possibly
have been played on a reel-to-reel machine, so the designers could
have used any tape speed they wanted.

I wonder if there are even video tape recorder speeds that harken
back to the original 30 inches per second?  Anybody know about that
stuff?  What did the Ampex VTR1000 run at?

D. Morton
IEEE Center for the History of Electrical Engineering

Ah, but they are related to the AC line frequency.  On a 60 Hz power
system, 78.26 RPM is the speed that a 92 pole motor turns at, 45 RPM is
the speed of a 160 pole motor, and 33 1/3 RPM is the speed a 216 pole
motor turns.  33 1/3 RPM even works on 50 Hz current with a 180 pole
motor, not sure what the Europeans did to get 45 RPM from a direct drive
table.  78.26 RPM was just an approximation anyway, so they probably did
their own approximation on that one.

Regards,

John Byrns

78 RPM was chosen in the days of spring wound turntables.  The AC line
frequency then wasn't good enough to use anyway.  When 33 and 45 were
chosen, home record players used shaded pole induction motors.  The
speed of these depended on line frequency, line voltage, load, and the
amount of "slip" the designers gave them.  The speed was generally
pretty far from synchronous speed.

Jim Mueller

The stated return address is incorrect to reduce the amount of junk e-mail I
receive.  To get the valid return address, replace "deadmen" with "dadoman"
and "stairnot" with "azstarnet".

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"But even non-reel to reel tape recorders invented later still  apparently
derived their tape speeds from that original 30 ips -- e.g. the modern
cassette runs at 1 7/8 ips  (half of 3 3/4, which is half of 7 1/2, which
is half of 15, which is half of 30).  The Elcaset of the '70s ran  at 3
3/4, as did the 8-track.  The big RCA cartridge of the 50s (discussed often
in this ng) also ran at 3 3/4, and the abortive 3M/Revere cartridge system
of the late '50s/early '60s ran at 1 7/8.  None of the tapes used on these
systems could possibly  have been played on a reel-to-reel machine, so the
designers could have used any tape speed they wanted."

Actually the RCA Instantape system was compatible with open reel, to the
extent that you could tear open the cartridge, respool the tape and play it
on an open-reel deck *if* that deck could handle quarter-track at 3 3/4
ips, which not all stereo decks could in the late 1950s.  RCA Records
actually released the first pre-recorded tapes in this format *before* the
Home Instruments division had a deck in production; Electronics Illustrated
got hold of some and respooled them to play on a Viking open-reel machine.

"I wonder if there are even video tape recorder speeds that harken  back to
the original 30 inches per second?  Anybody know about that stuff?  What
did the Ampex VTR1000 run at?"

The VR-1000 ran at 15 ips, and so did almost all of its 2" quadraplex
successors.  (Some machines in the 1970s had half-width heads and were
configured to run at 7.5 ips, allowing them to play a full-length movie
from one reel. These were used in at least one pay-per-view test project.)
A number of 1/2" open-reel machines in the 1960s and 1970s ran at 7 1/2
ips, and the 3/4" U-matic industrial format runs at 3 3/4 ips.

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<html><head></head><BODY bgcolor=3D"#FFFFFF"><p><font size=3D2 =
color=3D"#000000" face=3D"Arial">David Morton &lt;<font =

tape recorders invented later still &nbsp;apparently derived their tape =
speeds from that original 30 ips -- e.g. the modern cassette runs at 1 =
7/8 ips &nbsp;(half of 3 3/4, which is half of 7 1/2, which is half of =
15, which is half of 30). &nbsp;The Elcaset of the '70s ran &nbsp;at 3 =
3/4, as did the 8-track. &nbsp;The big RCA cartridge of the 50s =
(discussed often in this ng) also ran at 3 3/4, and the abortive =
3M/Revere cartridge system of the late '50s/early '60s ran at 1 7/8. =
&nbsp;None of the tapes used on these systems could possibly &nbsp;have =
been played on a reel-to-reel machine, so the designers could have used =
any tape speed they wanted.&quot;<br><br>Actually the RCA Instantape =
system was compatible with open reel, to the extent that you could tear =
open the cartridge, respool the tape and play it on an open-reel deck =
*if* that deck could handle quarter-track at 3 3/4 ips, which not all =
stereo decks could in the late 1950s. &nbsp;RCA Records actually =
released the first pre-recorded tapes in this format *before* the Home =
Instruments division had a deck in production; Electronics Illustrated =
got hold of some and respooled them to play on a Viking open-reel =
machine.<br> <br>&quot;I wonder if there are even video tape recorder =
speeds that harken &nbsp;back to the original 30 inches per second? =
&nbsp;Anybody know about that stuff? &nbsp;What did the Ampex VTR1000 =
run at?&quot;<br><br>The VR-1000 ran at 15 ips, and so did almost all of =
its 2&quot; quadraplex successors. &nbsp;(Some machines in the 1970s had =
half-width heads and were configured to run at 7.5 ips, allowing them to =
play a full-length movie from one reel. These were used in at least one =
pay-per-view test project.) &nbsp;A number of 1/2&quot; open-reel =
machines in the 1960s and 1970s ran at 7 1/2 ips, and the 3/4&quot; =
U-matic industrial format runs at 3 3/4 ips.</p>
</font></font></font></body></html>
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