[78-L] Diamond Disc mould.

[Malcolm Rockwell]

Seems to me that an inverted groove for an Edison cut 78 doesn't look 
like my first example (which is a "normal" lateral cut)


      * *                                        * * * * * *
   *      *                                      *           *
  *        *         but like this         *           *
*          *                                    *           *
*          *                                    *           *

(the example may be skewed but you can see what I mean)

You can see how a bifurcated stylus would work fine on the first - in 
stereo even - but not on the second. The amount of contact the stylus 
would have with the sides or the top of the second example would be 
minimal and probably very noisy - and only in mono. There would need to 
be a way for the whole mechanism - stylus, cartridge and arm -  to be 
supported allowing the stylus to ride freely on the top of the 
vertically modulated reverse groove, and do it without introducing noise 
in the playback. Tricky, unless you use a beam type recording lathe 
pitched to the recording.
Comments?
Malcolm

*******

On 5/2/2012 5:14 AM, Thomas Edison wrote:
> Re metal part.  To play a vertical master would you not want an upside down U shaped stylus to fit over the inverted, hill-and -dale groove? Such as the fancy term you used, I think is what you mean, or are you staying two trunicated styli that ride both sides of the groove. Mostly likely play them back on a liner tracking turn table.  You could make epoxy resin test pressings from them too  Norman B should be able to help you do that, since they are making new Diamond Discs.  It  might be possible to make a  metallic soap pressing   I can practice this, with a regular  lateral 78  stamper that I have and see if I can get it down to a science and let you.  I imagine if the wax is fildterd 4 times it should be pure enough for a clean copy, and almost like playing a wax master.
>
> Sincerely
>
> Shawn Borri
>   		 	   		
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