Re: [ARSCLIST] Exit Grooves on Shellac and Early Vinyl

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Hello,

Michael Shoshani wrote:

> "Copeland, Peter" <Peter.Copeland@xxxxx> wrote:
>
> >    When discs were mastered on wax, a small degree of runout-groove was
> >cut as the song (or whatever) ended, and then the cutter was raised from the
> >wax. Here in the UK, this runout-groove may be seen on His Master's Voice
> >acoustically-recorded 78s in late 1924 and early 1925, followed by a
> >*con*centric to catch the reproducing needle before it ploughed-up the label.
> >    After about March 1925, the wax would be taken to a factory well
> >away from the actual studio, where it could then be loaded onto a
> >machine dedicated to cutting eccentric grooves.
>
> Here in the US, the situation was similar with The Victor Talking
> Machine Company, yet slightly different. ........................etc.

I may be able to shed some light on the eccentric groove matter as it relates
to VTMC and the GC. First of all, there is a good picture of a machine for
cutting a set of eccentric grooves in wax in

[anonymous] "Recipe for Moulded Music", The Penguin Music Magazine, Ed. Ralph
Hill, No. IV, Penguin Books 1947, section of plates [no numbering] inserted
between pp. 32 and 33.

The fourth plate shows such a machine, and to the initiated it is apparent
that it hails from acoustic days, because the cutting stylus is mounted in a
two-part recording soundbox, complete with counterweight, which is actually
an old VTMC design, albeit without a diaphragm.

More precise knowledge may be had from a report written by J. Jackson of GC
after a visit to VTMC in September, 1923 (Jackson had been R. Sooy's
assistant or "counterpart" at the GC when Sooy went there in 1921 to rebuild
the recording department). Regarding eccentric grooves he reports two methods
of putting them in.

1) "The two eccentric grooves are put in the Wax Original immediately after
recording. A special machine is used ...... To ensure setting central on this
Machine, all Victor Wax blanks now have a Hard Rubber Bush fitted in the
back, this is not affected by the Plating Bath and does not wear and chip
away as the wax recess does. [GBN note: this is important, because the waxes
were used a number of times after being shaved and polished]

....... The two Eccentric Grooves are .030" apart, and the shape of the
groove as per sketch below [GBN note: not shown], the 19 deg-15 min angle
side [GBN note: to vertical] being to the inside of the Grooves [GBN note:
the other angle being 56 deg-10 min to the vertical]

2) "The work on the Shells [GBN note: metals] made previous to the grooves
being put in the Wax, is being done in the Workshop in the Recording
Laboratory, and the Grooves are put in the Positives. There are four
operations performed.

1. Roll out Concentric Ring.
2a. Continue last Groove to correct position with relation to shell number.
2b. Roll in 3" Concentric Ring
3. Roll in "Turn in" on last Groove.
4. Roll in Eccentric Grooves

......... the Roller used is the same shape as the Special needle used for
putting the Grooves in the Wax."

So, from the above we may learn two things 1) the grooves were not merely
coarser, but the flanks were very differently angled from the recording
groove, and 2) at some stage the grooves were prepared in the copper (which
was malleable, provided the current used in plating was not too high). With
nickel, that would not work. On some early Hanover manufacture of GC records,
very coarse grooves are noted for the run-out, and those have a definite look
of rolling about them.

Kind regards,


George