[78-L] 78 grove spacing

[Kristjan Saag]

 From September 1950 Deutsche Grammophon's Archive series 78's had 
variable pitch/ variable groove spacing, thus almost double playtime. 
Polydor also used the technique for some of their 78's.
The technique, with control amplifiers connected to the tape machine, is 
described on pages 649-650 in the Audio Cyclopedia.

Kristjan


On 2019-08-15 01:59, ron at fial.com.invalid wrote:
> I saw no activity, so I was just testing that everything was OK on the 
> 78-L server. Here is a question. I know that grove excursion must be 
> limited to keep loud low-frequency passages from breaking to an 
> adjacent grove when cutting a record. This can be done with level 
> limiter, volume compression and (egads) clipping and low frequency 
> limiting. I recall that in the vinyl era there were automatic means to 
> create greater grove spacing for loud passages. I could be mistaken. 
> What methods were used for 78-RPM records. Was someone riding the 
> volume control and watching the VU meter, when that came along. What 
> technologies if any were used and when did they come along. There may 
> have been allowance for the grove getting wider with many playings, 
> right? I suppose a microscope used on acoustic and early electricals 
> would reveal much. Any one here already know? Ron Fial 
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