[78-L] One or three holes?

[Graham Newton]

Milan P Milovanovic wrote:

> not so while ago, the discussion about details of lathes raised. I came 
> across this record sample

> http://youtu.be/tc2FrjRa9Os
> 
> It is clearly visible only one hole mark besides spindle. I always 
> thought that one additional hole on lacquer was reserved for amateurish
> type media and three additional holes for professional blank samples.
> 
> Someone knows what's in case here? Why is there only one? Could it be 
> possible that recording engineers used semi pro or amateur recording 
> blanks?

It depends on the type and design of the recording lathe.  The extra hole or 
three holes are drive holes to engage with a single (usually spring loaded) pin 
to prevent the lacquer disc from slipping as it is being cut for the master. 
Why some lacquers were supplied with three holes is a mystery, since I never 
encountered anything where more than one hole was needed.

All home use disc cutting machines used discs with at least one drive hole.

Many professional mastering lathes like Scully and Neumann used lacquers with 
no drive holes, only the center pin, and it was hollow to allow vacuum to be 
conducted under the turntable platter to hold the lacquer flat while it was 
being cut.

Lathes like Presto, RCA Victor and others found in broadcast studios mostly 
used lacquers with the drive hole since it was much cheaper to make a 
non-suction-hold-down turntable.




... Graham Newton (RCA Victor disc mastering engineer in a former life!)

-- 
Audio Restoration by Graham Newton, http://www.audio-restoration.com
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