PBS Idiots

Kinda like the political candidate that (before deregulation and 24-hour informercials) scheduled his ad late in the evening and at the end of it had the national anthem play then showed several minutes of test pattern. Everybody went to bed and missed his opponent's ad which came up next. (This may be an urban legend.)

Speaking of the "end groove", how many grooves are on one side of a typical vinyl LP?

(spoiler below)

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SPOILER: One.

Cheers! Rich

The only time a test pattern was aired was first thing in the morning, to check out the old tube transmitters, or at the end of the broadcast day, for the same reason. BTDT, used to have the 35 mm 'Indian Head' test slide.

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What? You haven't got a copy of "Monty Python's Matching Tie and Handkerchief" album?

It had 3 sides!

One surface had two concentric 11-minute grooves instead of a single 22-minute groove.

You had to trickily place the tonearm by hand if you wanted to hear both "sides".

Much was lost when they released it on CD.

Including the clever cover/sleeve illustration, for which there was no excuse.

Which reminds me I must show my kids how to play a phonograph. I wish I could remember where I stored the dust whiper.

Easy, to first order approximation. The disks spin at 33 rpm - call it 30 rpm to make the numbers easy. That is the same as 2 sec per revolution. Most single sides last about 25 minutes, i.e. 1500 secs, in which they will perform 750 revolutions. Thus there are approximately 750 grooves per side.

CBFalc>Easy, to first order approximation. The disks spin at 33 rpm -

For your next question: How many sides does a Mobius strip have?

One.

CBFalc>One.

You know this because you can draw a line along the whole thing without lifing your pencil.

My question was meant to make you think how the phonograph stylus gets from one of the 750 groves to the next.

Without lifting the tonearm.

It depends on how fast it's spinning.

Handkerchief" album? It had 3 sides!

What 750 grooves? In 45s, LPs, CDs, and DVDs there is a single spiral groove/track per side. (with a very few noted exceptions)

JeffM set the following eddies spiralling through the space-time continuum:

About as many as a Klein bottle.

Mensanator set the following eddies spiralling through the space-time continuum:

Easy when there's something stuck in the groove causing the stylus to jump. I called this sort of blemish a sticky-clicky when I was a kid, somehow I've never found a better name.

Rich Grise set the following eddies spiralling through the space-time continuum:

They managed a bit better than that with the CD version of The Beatles' "Sgt. Pepper" album.

It's a shame the Chandos disc of BBC test card music came out after the end of the vinyl age. In its CD incarnation the disc ends with about 20 seconds of the 440Hz test tone. In an LP version this tone could well have been recorded onto the end groove - an end groove left wide enough not to trigger any automatic stop.

Speaking of the end groove, the earliest LP's had eccentric end grooves like the old 78's, while all the 45's I knew had concentric end grooves. Why the eccentric groove originally, why the change to concentric for 45's, why first the one then the other for LP's?

(Note: "eccentric" is here used literally. A stylus caught in an eccentric end-groove will continue to move back and forth as the record turns, one caught in a concentric end-groove will stay at a fixed radius.)

p.

Interesting theory. One minor problem, it's completely wrong. If a tonearm jumps out of the groove, it's thrown OUTWARD from the disk center and repeats the groove it just played.

Even if you actually had a record with concentric grooves, this idea cannot explain how the tonearm would advance to the center of the disk from the outer edge.

Just as well. By the way, the expression "sounds like a broken record" refers to something said repeatedly. This could never had come about if a skipping tonearm advanced forwards.

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That would have been a neat trick considering there's no such thing as an "end groove".

Of which there is no such thing.

Why would I believe this when everything else you said is flat out wrong?

False premise. There's no such thing as concentric grooves.

Yeah, why would they change from something they didn't do to a completely different thing they didn't do?

You're halucinating. Did you ever shine your black light on a stack of 45's and see how the black vinyl changed color to various shades of green and reddish brown? A real head trip.

Lp disks don't seem to show this phenomena.

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Can be seen here:

(scroll to bottom of page.)