Audiophiles and Vinyl Records Experts! Let's Discuss About Grooves...

Based on my experience as a collector, I have always noticed that any scratches on the surface of the vinyl records, have a different impact on the quality of listening on the grounds that we talk about mono or stereo records.
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Now, from the little information I have, I understand that the groove of a stereo record can be considered as having the shape of a V with an angle of 90 degrees: the two walls of this groove respectively contain information for both left and right channels : the stylus then reads the information placed vertically on the walls of the groove.

It is not the situation with regard to the grooves of mono records: in this case, the information for the single channel are not contained on the walls of the groove, but rather on the bottom of the groove: in this case, the stylus reads information placed "horizontally" on the bottom of the groove.

If this summary information is correct, it can be inferred for example, that any scratches on the surface of the vinyl record procure less damage to the final sound if they are present on surfaces of mono records: a not too deep (paper scuffs etc.) scratch is not going to affect the information contained on the bottom of the groove.

As regards the surfaces of stereo records, instead, they are much more susceptible to scratches as they go directly to damage the walls of the groove, that it's as to say the area in which are contained the information for the stylus.

Any type of information or further observation, is very pleasing.
Let's discuss!

 

Taking into account this information, we can deduce that the famous Led Zeppelin II 1st USA press mastered by Robert Ludwig was characterized by a dynamic range too wide compared to what some turntables of that era could tolerate: in some models of turntables it seems that the "Hot Mix" did cause annoying skips.
Evidently, the walls of the grooves had too large "steps"compared to those that some turntables could tolerate.

At this point, I think there is a myth to dispel: the one whereby the depth of the groove affects the quality of the sound.
Based on what I have written before, in fact, the depth of the groove depends on the amount of sound information therein recorded: if groove's walls are high, evidently they have a pretty wide dynamic range and contain more sound information for cartridge.
Thus, the depth of the groove depends on the type of sounds engraved therein.

The depth of the grooves is very evident especially while brushing our records: records that have deep grooves dry before than records that have shallow grooves.....

 

My understanding was that information is encoded in both the vertical and horizontal planes. One (can't remember which) carries L+R (i.e. a mono sum) and the other carries L-R (stereo difference). The phono stage sums these signals in one channel and subtracts them in the other:

i.e. L+R+L-R, which resolves to 2L
and L+R - L-R , which resolves to 2R

IME a lot of surface marking doesn't sound and a lot of audible damage is invisible to the naked eye.

 

While the stylus only moves horizontally when reproducing a monophonic disk recording, on stereo records the stylus moves vertically as well as horizontally: but I know that (but I'm not 100% sure..) in a stereo groove the information is encoded in the walls of the groove and not in the bottom of the groove.

 

I'm pretty sure that mono LPs have information only in the horizontal axis: the vertical walls of the groove are unused. Therefore, if we play a mono LP with a stereo cartridge, the stereo cartridge will pick up vertical information as well, which is totally noise: this explains why we must always listen to a mono record using a mono cartridge or using a stereo cartridge but switching in mono our amplifier.

As for the stereo records, now I doubt if the grooves of stereo records also contain information on the horizontal axis as well as on the vertical one: I'm pretty sure that the two walls of a stereo grooves contain information for both channels (left and right), but I'm not at all sure if the horizontal axis of a stereo groove contains information for cartridge; it would be interesting if some expert could answer this question, eventually stating what type of information is encoded in the horizontal axis of a stereo groove.....

 

So: indeed, on-line there is not very clear information especially for someone who is not a technical expert (like me).
Anyway, I managed to find this information, hoping that they are as accurate as possible (but I'm not sure....): information is encoded on the walls of the groove in both mono and stereo records, but the difference is this one:

MONO grooves are produced by cutting a V-shaped groove with a laterally-oscillating stylus: this forms grooves of a wavy shape, and grooves have constant width and depth; so there is no vertical information.

STEREO recording uses a laterally and vertically-oscillating stylus. The stereo cutter-head has two complete electromagnetic mechanisms arranged in such a way that they apply each channel of sound to a common stylus. Since the groove is V-shaped, it is possible to have two grooves in one, in effect: each wall of the "V" represents a different channel (left and right) and has a distinct wave pattern to be picked up by the stylus.
Stereophonic records should never be played on a monaural record player: damage can result, as a monaural stylus is not designed to pick up vertically-cut grooves.

An expert is required to correct or to confirm...please.

 

Yes, Stefano G is correct. L+R and L-R was not used for Stereo LP discs, that system was considered but didn't get used. It did get used for CD-4 Quadraphonic LP discs and you know the issues with it. Sum and Difference is how FM Multiplex Stereo is done.

 

Well, now let's take a look to the difference between groove depth: groove depth is nominally (standardized) deeper for mono; min groove depth spec is 1.5 mil for mono and 0.7 mil for stereo.

Now, as I already said before, I noticed a difference between mono records and the stereo ones: according to my observations and experience, in fact, surface scratches and paper scuffs impacting less on mono records than on stereo records.

What I liked, it's to ask if anyone else has noticed the same thing, and if possibly the difference in depth between mono groove and stereo groove could have some influence about this subject...

 

In this regard, I totally agree.

 

I think the two walls of the V-shape represent L and -R (or maybe -L and R). The minus on one side is important: if the recording is mono then L=R and therefore the movement of the two sides are opposite (because of the minus sign.) Now the two sides of the V-shape are at 90 degrees (each at +/-45 degrees to horizontal) and their movements are opposite. The result is that the stylus only moves from side to side.