This might need to be CS instead of GQ but its a mechanical question, not performance.
I had a sudden urge to hear Little Willie John’s original version of “Fever” (Peggy Lee’s is a cover) so I called it up on YouTube. The video showed the record spinning and the needle being dropped on it. Since the song is from 1956 the record was a 78.
After the song ended the arm reached the runout groove and took about two laps before it was lifted. The groove was one of the non-concentric ones where the arm moves from side to side as the record spins and I got to wondering why it was made that way.
LPs have a runout groove concentric to the hole in the record and I’m not even sure all 78s are non-concentric – it’s been a long time since I’ve laid eyes on one – so I’m wondering why at least some of them had the old wiggle.
Was it to trigger the changer mechanisms of the period?
I could swear I’ve seen this behavior on LPs, perhaps while trying to suss out the meaning of the Sgt. Pepper coda (apparently I’m the only one who hears, “I never go see Annie”). But that was 40+ years ago and it’s been at least 25 since I’ve laid needle to vinyl.
Be that as it may, the record had the proper label on it and it was a 78, as @LSLGuy’s link shows.* The question remains unanswered, though: Why the wiggle?
Some poking around (well, reading wiki) suggests that the stylus getting picked up and returned isn’t triggered by how close it is to the center of the record, but rather, how fast it’s moving. When it gets to the run out groove, it’s suddenly moving much faster than before and the mechanism gets triggered.
If the run out groove were elliptical or circular but non-concentric, it would move the stylus faster (at one point, slower at another) than a spiral could.
Why they’d have to do that, I don’t know. Maybe they were just trying something out. Maybe some record players of the time weren’t getting properly triggered. Maybe they just wanted to be different so their record would stand out more.
Maybe it’s the sideways velocity because, while you’re correct, the needle’s speed in the groove would speed up and slow down a bit in the runout, I don’t see how the change would be detected by the mechanism.
That sounds over complicated. Why not just a switch that’s triggered when the arm is at a certain angle? I suspect the shape of the runout groove serves no specific purpose, but is just a variation in the pressing process.
Obsolete technologically, maybe, but since they were cheaper to make and millions of people already had 78 machines, they continued to be made throughout the 50s, especially on smaller labels, like the r&b producing King Records.
Nobody seems to agree when commercial music 78s died out. This archived page from Recording History says:
The date of the very last 78-rpm record is not known, although some claim that the last one issued in the U.S. was Chuck Berry’s "Too Pooped to Pop " (Chess 1747), released in February 1960. There were almost certainly later released on small labels, and there are documented cases of 78 discs released as late as 1961 in Finland
Without further actual knowledge that’s sure the way I’d bet when looking at any sort of 1940s & 1950s “automation”. The simplest thing imaginable was just barely within the state of the art.
Actually it would be way before that. First a literally wax disk is inscribed with the groove by a cutter. This is when the runout groove would be decided. An impression is made of the disk in a low-temp melting metal so the grooves now stick up, then a metal master where the grooves are back in again.
Finally, stampers are made from the master and these are used to press the records. New stampers can be made from the master as they wear out which is why they go through this multi-step process.
The pressing process was fairly hands on, the labels are placed on a central rod on each stamper, and the actual stamper is itself centred on the same rod. This rod creates the hole in the middle. So in principle everything should be concentric. But the labels, being just flimsy paper placed by hand may end up moving as the record is pressed. A lump of hot plastic material is placed in the middle of the lower stamper and the press closes, extruding out from the centre. A slight misalignment of the lump might cause the label to shift as the pressing operation occurs. So actual eccentricity of the grooves would be unusual, but an off-centre label much more likely. Nakamichi made an insane turntable that automatically measured and corrected groove eccentricity. It wasn’t a success, despite the amazing engineering.
A thing about these old automatic players is that there was usually only one motor. Everything was a clever setup of cams and levers that engaged power from the same motor that spins the record. The idea of electronic control or, heaven forbid, the expense of another motor just wasn’t on. I could imagine a design that needed the tonearm to pick up a bit of lateral momentum before it was able to trip the lever that engaged the arm return mechanism. There is of course an element of chicken and egg here. The runout grooves existed in the format before automatic players did. But once the design of automatic players became ubiquitous, there would be an expectation that records would continue to provide such run out grooves.
Typically the pressing master was electroplated onto the acetate master. Then, a second electroplated inverse version electroplated off that. This second version is known as the mother. Multiple mothers can be made from the master. From these mothers a third plating step produces the actual stampers. Many stampers can be made from a single mother. The process allowed for a lot of stampers to be produced.
I can’t remember the artists or the record name, but there was an audiophile jazz disc named after a thread of lacquer from the disc cutting process wrapped around the heated cutting stylus and caught fire. The artists joked it was because their playing was so hot it caused the fire!
As the lacquer is cut, the stylus is heated to help it cut more smoothly. The cutting lathe also has a small vacuum-producing tube mounted next to the stylus. It vacuums up the continuous thread of black lacquer as the grooves are cut. This spiral of waste lacquer is called the chip.
Eccentric runout grooves on 78 RPM recordsd would cause the arm to move backwards, which was a signal to the record player to stop. Only some record players had this feature. An eccentric groove was a more reliable signal that the record was over than simply using the angle of the arm, because recorded grooves didn’t all have the same inner diameter.
78s without eccentric runout grooves would usually have an increased groove pitch after the recorded material that would lead to a circular groove at the inside of the record. Some record players would shut off when they detected the arm moving quickly across the record.
