Re: [ARSCLIST] Dynagroove, was Record tracking

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad


Lou Judson wrote
> Pardon this if it is OT - I am curious about this. I have only heard a 
> few Dynagroove records, and rather than do laborius research, can 
> someone describe what is going on with them? All I remember about them 
> is that they had a raised ridge around the circumference to keep them 
> from rubbing together on the grooves... What are the issues about the 
> mastering and pressing? Offlist if I am the only one who wonders...


----- you are probably not. The whole idea with Dynagroove is that they used 
a tracking simulator in the cutting amplifier circuit. This was meant to 
predistort the groove shape so that it would provide the correct waveform 
when traced by a spherical stylus, that is a circular conical stylus with a 
spherical tip of the correct tip radius. When you trace it with a line 
contact or even an elliptical stylus, that is, less line-like, then you get a 
distorted signal, because that is what the groove is. Teldec had a similar 
system that had different electronics. It was news to me (a prior post) that 
there might even be master tapes that contained predistorted signals. That 
solution has not been documented, to my knowledge.

An elliptical stylus could be an elliptical cone with a rounded tip or a 
circular cone with two flats ground, almost creating a chisel edge, and that 
edge was then rounded. This would create an oblong shape that only traces at 
two points of the groove. The latter is also sometimes called "truncated 
elliptical". Incidentally, Robert Parker used a truncated elliptical stylus 
turned 90 degrees for his jazz transfers from 78s - using the long side along 
the groove. Apparently this created distortion, i.e. high frequency content 
that premitted him to low-pass filter to remove noise and still have some 
treble. I never liked them.

Kind regards,


George