SWAP: 60hz Lyrec Motor SM8/3A for 50hz Lyrec Motor

[opcode66]

Or you can cut the supplied audio for an unequivocal log of the drift per rotation. Which is of concern to me, your mileage may vary. Any appreciable inconsistency causes issues in the visual representation. In the case of speeding up or slowing down the image shows a distinct radial stretching distortion. In the case of both speeding up and slowing down or fluttering, the image does not look clear and precise. It will also tend to have some aliasing or rough looking lines. But mostly, it looks like an s shaped distortion.

So if I'm a DJ and I am playing music that has inherent fluctuations in speed due to the inconsistency of the platter motor used to cut the record, then I'm always going to be having to tweak the pitch on the turntable when doing blends. Much more so then I would with a record that's cut stably. I typically hold a blend for up to 3 minutes. So, long term drift is important to dj's. To say doesn't matter ignores one of the largest audiences for vinyl records, which are DJs.

[gold]

I meant that W+F is not a useful metric for long term drift. It is meant to describe the behavior of one device. Not how two devices interface together. In pro audio speak, getting turntables to play together would be a synchronization issue. Since it is impossible to lock two turntables together with repeatable accuracy it was never a concern to designers. The example of a DJ is "off label use". Important for that but unimportant for normal listening.

[Greg Reierson]

I haven't tired it yet but I'm wondering, how much does the pitch motor stability affect the result?

[gold]

I haven't tired it yet but I'm wondering, how much does the pitch motor stability affect the result?

That's a good point. The straight line test doesn't isolate the turntable from the pitch motor. So the instability could one or the other or both.

[tubefan]

On the 66 and 70 the pitch motor has DC tachogenerator feedback, so it seems like there wouldn't be much 60Hz there unless something's broken... The Lyrec has no such assistance...

[opcode66]

The instability of the pitch motor results in a compression or stretching of the image. It doesn't create the raidial effects like the platter motor. It is actually considerably less of an issue than the accuracy of the platter motor from a visual perspective baecause each revolution of the platter is still in line even if the spacing of each revolution isn't.

Long term stabiltiy of pitch is something I'm interested in. It may not be a goal of all cutters. If you would like to see how much your platter motor drifts over time (as much or as little time as you wish) please try cutting my cross test.

Audio that will create a straight line going from the outer diameter to the inner diameter will always create a straight line no matter how instable the pitch motor is (assuming the platter motor is 100% stable). How filled in the line will appear is a direct result of the stability of the pitch motor. It will just simply look more or less filled in depending on the accuracy of the pitch. But as long as the audio is timed appropriately and the motor speed is accurate, the line will always appear straight. Regardless of pitch. Boom!

[EmAtChapterV]

Back before Opcode66 made the Groove Graphics program, I used to plug a digital metronome into the cutting amp, set to 3/4 time at 100 beats per minute. I never did get it quite right on the Rek-O-Kut though, with the idler drive it was always a little fraction of a percent fast or slow, depending on how deep the groove was and how close to the center the cut was.