Paul's point is well taken. A digital speed readout renders the whole line frequency issue moot. But, if you don't have a digital readout, I strongly recommend the KAB SpeedStrobe:

Go to this page:

Click on Accessories and scroll down until you find the SpeedStrobe, then click on that link. The SpeedStrobe has markings for most standard "78" speeds, plus 33 1/3 and 45. It comes with a hand-held LED light source, which digitally generates a precise 60 Hz illumination, so it can be used anywhere, regardless of the native line frequency. The LED is bright red and cuts through any amount of ambient light in the room. 

As Crazy Eddie used to say, "Get it NOW!"



Gary Galo
Audio Engineer Emeritus
The Crane School of Music
SUNY at Potsdam, NY 13676

"Great art presupposes the alert mind of the educated listener."
Arnold Schoenberg

"A true artist doesn't want to be admired, he wants to be believed."
Igor Markevitch

"If you design an audio system based on the premise that nothing is audible, 
on that system nothing will be audible."
G. Galo

-----Original Message-----
From: Association for Recorded Sound Discussion List <[log in to unmask]> On Behalf Of Paul Stamler
Sent: Sunday, January 20, 2019 7:49 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] Playing speed

On 1/20/2019 3:54 PM, Steve Smolian wrote:
> Is there a formula to covert a specified playing speed at 50 cycles to 
> the playing speed at 60 cycles?  Example: 75 rpm at 50 cycles, what 
> speed at 60 cycles?

No formula; If possible, play it at the same speed it was recorded at, regardless of line frequency.


> Steve Smolian

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