Regarding Richard Brandle's question about how turntable speeds were
devised, I have also wondered the same thing.

The 45 r.p.m. record was an RCA product, and the 33-1/3 r.p.m. LP album
was Columbia's competing format.  Both were introduced to the public in
1949-50.

I can recall reading in an early magazine that the 33-1/3 speed for
Columbia's new LP album records came to be because a lathe in the test
lab creating the LP record just happened to turn at that rate.  I find
this hard to believe, so I am interested in knowing if this was truth
or just speculation.  Didn't certain models of the early (1928 or so)
Victor Automatic Electrola play 33-1/3 r.p.m. discs also?

I recall hearing that 45 r.p.m. was found to be the slowest you could
turn a recording without losing appreciable quality.  That is why
theoretically most 45's sound better than 33-1/3 LP's.  45's have less
information per inch of groove, sort of like running a faster magnetic
tape speed improves quality.  Most professional nightclub DJ dance
singles are pressed to run at 45, and are always 12" in format to get
the grooves farther apart so they may be recorded louder.

I would guess the 45 r.p.m. center hole was made 1.5" in diameter as
part of the RCA marketing plan, and partly technical.  The first 45
r.p.m. record changer, produced by RCA in 1949 in conjunction with
their new 45 records, was able to stack the recordings without the need
of a stabilizer arm.  From a marketing standpoint, in 1949 most home
turntables played only 78 r.p.m. discs, and in order to play the new
RCA 7" 45 r.p.m. records, or Columbia's new 33 1/3 r.p.m. records, you
had to buy a new turntable.  It wasn't until the early 1950's that
2- and 3-speed record changers even came into existence.

Just as a sideline, 78 r.p.m. records were produced until 1958, and
the first jukebox capable of playing 45 r.p.m. records was the Seeburg
M-100-B of 1951, a fifty record / 100 selection machine. 33 1/3 LP
albums and 45's are still produced today contrary to popular belief.
There are still a lot of vinyl-playing jukeboxes out there on the
street making money.  Current record lists stock most top 40 radio hits
on new 45's, as well as all the older hits all the way back to the
1940's.

John D. Rutoskey

 [ 33.33 rpm was the standard speed, established circa 1930, for radio
 [ broadcast transcriptions, so it's no surprise that a lab turntable
 [ existed already.  The original 3-minute 45 rpm disc featured deep
 [ grooves, widely spaced, so that the forces on the needle and the
 [ ceramic pickup wouldn't destroy the wall of the groove.  Why so
 [ much amplitude?  Because the inexpensive phono for the mass market
 [ had fewer vacuum tubes, to minimize the cost, therefore more voltage
 [ from the pickup was necessary.  The contemporary disc jockey (DJ)
 [ needs the high power at the needle to help prevent acoustic feedback
 [ in his high-intensity environment.  (Wear ear protection!)  -- Robbie