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Topic: vinyl: true or joint stereo? (Read 2965 times) previous topic - next topic
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vinyl: true or joint stereo?

i am having a discussion with a co-worker about vinyl being true stereo or not. i have been trying to find some articles about this, but either i am using the wrong keyword or there is just not much info to be found on this subject (i doubt it...). does anyone know an article about how vinyl is 'read'?

thanks in advance

vinyl: true or joint stereo?

Reply #1 –
Ciao..

 

a shellac or vinyl is 1.ch. or can be 2.ch.
on each side of the groove..
(extreme cases shows 2.5ch.
where the .5 would infact be joint)


that`s a fact.
if a person argues with you about vinyl
been true stereo..  urge him to get
he`s head out.. of whatever it`s inn..

(i assume he`s not old enough to
have lived with vinyl. 
how .. do he think the record would be
produced.. otherwise..))

vinyl: true or joint stereo?

Reply #2 –
Actually, this could be a really interesting debate.

For one thing: define true and joint stereo...

In audio coding, "true" stereo means that the channels are coded separately. They don't have to be coded independently, just separately, as separate left and right signals. They're not independent, because, if the left channel was silent, you could give all the bits to the right channel.

In audio coding, "joint" typically stereo means that you take advantage of the similarity between the channels, or effects in human hearing when listening to stereo, to code two channels for efficiently. Common methods are M/S (mid/side) stereo, where instead of left and right, you code the sum and difference; or intensity stereo, where, for certain frequencies, you combine the two channels, with some information as to how the combination signal should be sent to left and right channels upon decoding (usually just panning information; phase information would also be possible).


Now here's the problem: M/S stereo itself is lossless. You can transform Left and Right into Mid and Side, and back again, as many times as you want, with no loss at all. It's only when you code the M/S signal with a lossy codec that you lose something. So, technically, pure M/S is still true stereo, because you can get back to left and right very easily. Lossy coded M/S is joint stereo, because you can't get back to left and right perfectly (not that you can ever get anything back perfectly after lossy coding) and because you've not coded the two channels separately.


Right - part two - how are stereo signals recorded onto vinyl? go here:
http://www.vinylrecorder.com/stereo.html

Simply: left channel on the left groove, right channel on the right. (but follow that link for some helpful pictures). So, they're independent. In the same groove, but at 90 degrees to each other, so one can't interfere with the other. In theory.


However, here's where it gets really messy: You could also look at the vinyl recording as being M/S. The "mid" or "sum" signal modulates the groove in a horrizontal direction, and the "side" of "difference" signal modulates the groove in the vertical direction. It doesn't matter whether you think about L+R or M+S, you get the same result in the record groove. However, in a way, M+S makes more conceptual and engineering sense - "mid" is equivalent to a mono signal, which makes mono and stereo records perfectly compatible.

This is more than a coincidence: A stereo record which happens to carry a mono signal gives the same result as a mono record. What am I talking about? Well, mono came first. When stereo was introduced, there were other options which would not have been compatable! (e.g. picture 3 in the above link was actually proposed as a system!)


If vinyl recording can be thought of as being M/S (which it can), then it's still "true" stereo if it's lossless (and hence perfectly reversible, so you get perfect L/R). And there's the problem. Vinyl recording isn't lossless. That's why we have CDs

Seriously, there is a connection between the two channels. Not in theory, but in practice. In theory, the two signals at 90 degree to each other can't interfere. In practice they can. In theory, the M/S way of thinking about it should eb equivalent, but in practice there are greater restrictions on the "side" or "difference" signal than there are on the "mid" or "sum" signal. Which should remind us of mp3. mp3 JS encoding hopes that there's less information in S than M (or in S+M than in L+R), so that it can be encoded with fewer bits. However, if this isn't the case, it can change modes and encode well anyway. Compare this to LP, where it's hoped that there's less information in S than M. If this isn't the case (i.e. if you try to cut a large out-of-phase signal), then the stylus may mistrack or jump the groove.



So, in conclusion, vinyl is not Joint stereo of the "Intensity stereo" type (which is the only kind of joint stereo that most people understand), but it could be thought of as Joint stereo of the "M/S stereo" type.

I think the correct answer for your friend would be that it stores all frequencies of both channels separately, and leave it at that! If pushed, you could admit that there can be cross-talk between the two channels, but this isn't intentional, and is minimised in good equipment. There is no attempt to merge the two channels, which is what happens in Joint "intensity" stereo.

Cheers,
David.

vinyl: true or joint stereo?

Reply #3 –
Ciao..

aroundthenaround, around_aroundthen...

well. here you go.. a quicky.. & and termly one..


vinyl: true or joint stereo?

Reply #4 –
Quote
Ciao..

aroundthenaround, around_aroundthen...

well. here you go.. a quicky.. & and termly one..



The words are English, but the meaning escapes me!

Cheers,
David.
 

vinyl: true or joint stereo?

Reply #5 –
Ciao..

jezz.. this was hot..
6. standing memz. in this tread..

@david..

the first.. is lyrics by johnny lightfoot..

and by.. "a quicky.. & and termly one"
i simply meant that even though our replies
was quite different.. i think the output
was pretty alike.