Run out grooves 78s

[Kris D]

Hi - My friend and I are preparing for a direct to disk 78 session coming up (microgroove 10inch- vinyl) and have been debating how to do an authentic lockgroove. On some of the shellacs we have examined the lock groove is off center and looks to be done after the recording was complete. Some contain double locks, some have no run out to the lock groove from end of side?? Was there a standard at the time or did each company have its own method? Any info would be appreciated.
Thanks
Kris

[Jordiphon]

Hi.
Those off-center grooves were pressed in Victor records to activate the mechanism in early Victor changers:

"Automatic Function is possible with VICTOR RECORDS ONLY, and of that only those that have the oscillating or oval end-groove."

Extract of the description of this video:

http://www.youtube.com/watch?v=q2O2z8iaAMY

[Aussie0zborn]

You can do the eccentric lock-out groove on Neumann lathes up to the VMS62 which is actually an AM32B with a VA62 gearbox. So, any neumann lathe up to the AM32B.

If I remember correctly, you do a lead out groove, move the lacquer disc off-centre and then cut a locked groove. This locked groove is then eccentric (off-centre) to the centre hole. So you are quite correct in your observation that the locked groove is cut after the recording is complete.

Andy B might be able to best answer this question.

[andybee]

Ha ha, I have a AM32B, but updated with vinylium pitch.
Nice info, for the off center runout groove
But, how do you cut a offcenter groove, without a second
hole, drilled in the laquer?
I won´t remove my centerpin of the lathe...
I think, a "standard" loop will also do the job.

[greybeard]

Hello,
each record company essentially had their own lockgroove style. Victor Talking Machine Co. introduced their double eccentric lockgroove ca. 1920; the grooves were deeper and also with a skewed cross-section. They were frequently rolled into the mother. Why emulate that if you are not doing a replica Victor (or HMV for that matter)?

Pre-EMI merger Parlophone frequently just had the runout ending in a locked groove.

If you are cutting a 78 rpm record, why not also use the appropriate groove dimension? An LP cutting stylus will take it, the lacquer is definitely thick enough so that the tip does not catch aluminum, and the only deviation from a "proper" profile would be the smaller tip radius. But this smaller tip radius means that you can play the record perfectly with a modern LP replay stylus. However, remember to have a groove pitch between 90 and 120 grooves per inch.

[Kris D]

Our reason for wanting to cut micro/non 78 tip styli was to make the record more accessable in playback. Are you suggesting to increase the groove depth but use a small mil styli?

We are cutting this with either an Arcturus with a 2B or a Presto 8D with grampian C - so just add more counterweight for the wider groove?

Thanks - Kris

[greybeard]

yes, Kris D, it would work. Groove width ca. 150 microns or a bit less. The advantage is that the record looks more coarse-groove, the disadvantage is that you will get a shorter recording time: max 3½ minute for one 10" side. But the small radius will ensure that the record can be played with a microgroove stylus as well as a coarse-groove stylus. In "old" terms, if you used a 1950s gramophone with crystal pickup of the kind that you could rotate: microgroove RED and standard groove GREEN, you can actually use both.

To be absolutely accurate you would reduce the counterweight, because it sits on the other side of the pivots.

It is cheating a bit, but you may practice proper timing and levels by recording digitally before the real thing.

And oh, I was sort of taking it for granted that you cut lacquers for later processing.
Good luck!

[Aussie0zborn]

Hey Andy, you need to read the instruction manual for the AM32B - its all in there. I had one and I can assure you it does it without removing the centre pin from the turntable. The lacquer had a second hole. I also had a VMS62 which is in fact what you have but never had an instruction manual for this lathe so can't be 100% sure if it had that facility. I also had a VMS70 and I can assure you that lathe does not cut an eccentric groove. Cheers.

[subkontrabob]

Hey Andy, you need to read the instruction manual for the AM32B

any chance of getting a scan?

[subkontrabob]

Our reason for wanting to cut micro/non 78 tip styli was to make the record more accessable in playback.

It's a little counterintuitive - there are not so many "microgroove-era" turntables with 78 rpm speed - you would actually decrease "accessibility". Even more so, as it would be harder if not impossible for gramophones to track your microgroove record.

With my 78 project (standard groove cut), the vinyl test presses can be played back on gramophones AND with microgroove needles.

[Cutterwoller]

I did some locked eccentric grooves on some 78s the other day. On a scully standard type. Cut the music then do the coarse scroll and lift the head as it reaches the end of the lead screw whilst still scolling (manualy). Then remove the centre pin, off set the disk by about 1/8", tape it down, cut the lock grove and sent them to the factory, came out nice.

In the old days, they had a seperate lathe with an off centre pin.

L