Investigating beforehand...

[Fergo]

Hello there everyone. I'm Fernando and this will be my first post. I am working the idea of getting my first lathe done. Im looking to make it as less electronic as possible.
Through my research I've got to the conclusion that when live recording a lathe, the laquer disc will have a stable speed (33 1/2 for example) and the advance of the recording arm will be at a stable speed as well. Would it be possible to coordinate through gearings the advance of the arm and leave the width of the track to be coordinated through the cutting needle?
The question is, am I in the right direction or am I misreading the information?
My plan was to get a nice motor working to have a whole gearing set so that for every 33 1/2 spins of the plate the arm advances the relative length ( I think it is 118 lines per cm.) Thanks a lot, and sorry on the metric system, but when I change to inches I always fuck up.

[Soulbear]

Hi There,
The RIAA Disc Dimensional Standards are posted here on the forum :- https://www.lathetrolls.com/viewtopic.php?f=8&t=7307 A 7" single's "Cutting Area" is specified therein.

My plan was to get a nice motor working to have a whole gearing set so that for every 33 1/2 spins of the plate the arm advances the relative length ( I think it is 118 lines per cm.)

Excuse me for "Rounding-Up/Down and Approximating" but if we take the "Cutting Area" to be 30mm ish or 3cm, at your proposed lines/cm this would be 3 x 118 = 354 lines and 354 lines/33.33RPM would mean you'd be laying down tracks of over 10 mins duration, on a 7" single?? Not possible with any meaningful "Recording Level" The grooves would simply "Overlap" into each other and you'd need an Amplfier with the output of a Saturn V Rocket for any reasonable level of "Playback". This proposed pitch is possibly therefore far too "Fine" and needs a little rethink maybe eh?
Regards Soulbear

[boogievan]

Just to clarify - we want your cuts to be at thirty-three and a _third_ RPM... (or 45). (:

118 lines per centimeter = 299.7 LPI, which is a great base pitch (i.e., ok for silence and quiet musical passages), however, as Soulbear points out, that would need to be sped up for forte passages - to as coarse as, maybe, 50 lines per centimeter. (In metric lands, one usually refers to the amount of land left between the walls of adjacent turns of the groove, rather than the number of center "lines per...").

Hélas, having (only) one pitch will be, either, wasteful or wanton (e.g., twining turns)... If you can vary the pitch with some kind of visual feedback (VU-style or numerical display) and repeatable stability, you'll be much closer to 'cooking with gas.'



- Tim E.