Surface Noise

[emorritt]

Again, it makes NO difference which direction the stylus is moving; up, down, left or right - CUT means something like chip is coming off the surface of the disc and either being blown or sucked away. Embossed means NOTHING is coming off the surface of the disc - the material is being DISPLACED and not REMOVED. What Peter King is doing is EMBOSSING - nothing is cut away. What people with the Vinyl Recorder or the Kingston are doing is CUTTING - something is being CUT away.

[Serif]

It is slightly confusing, but a modern stereo record (since 1958) is actually neither lateral nor vertical, but two in-out motions moving at 45 degrees into the record material. ...

What if the stereo cutter is fed a signal to both cutting coils that is monophonic, but the right channel is 180 degrees out of phase with the left... Would not the resultant groove be strictly hill and dale?




Thanks,
Andrew

[Serif]

Again, it makes NO difference which direction the stylus is moving; up, down, left or right - CUT means something like chip is coming off the surface of the disc and either being blown or sucked away. Embossed means NOTHING is coming off the surface of the disc - the material is being DISPLACED and not REMOVED. What Peter King is doing is EMBOSSING - nothing is cut away. What people with the Vinyl Recorder or the Kingston are doing is CUTTING - something is being CUT away.

I'd venture that what non-cutting disk recorders are doing should actually be called IMPRESSING, rather than EMBOSSING, since other material embossing means raising the image above the substrate. Impressing is pushing down into the substrate, as with a stylus... (I realize that history decides terminology, in spite of one's preferences...)


Other than surface noise characteristics, the playback stylus may not know the difference between a vertical-cut hill and dale record and one which is, technically, impressed (without removal of substrate).




Andrew

[opcode66]

What if the stereo cutter is fed a signal to both cutting coils that is monophonic, but the right channel is 180 degrees out of phase with the left... Would not the resultant groove be strictly hill and dale?

If the exact same signal is given to both left and right coil then yes, the resulting groove is just hill and dale.

However, in the real world, rarely does left channel match the right. That will cause both vertical and horizontal movement of the cutting stylus.

There is a superb animation on Souri's site that explains this.

Scroll down the page to where it shows a 45/45 stereo cutterhead cutting a stereo groove.
http://www.vinylrecorder.com/stereo.html

[maniman]

Guess confusion between vertical mono cutting , and when say "the vertical" in stereo cutting , obviously cutting in stereo at 45 is a combined evolution of a vertical system and a lateral (horizontal system) , the mono mix elements are more like vertical and the stereo elements are more like lateral , the way of removing the chirp arent significantly related with the stereo modulation , not ?

Regards

[Serif]

What if the stereo cutter is fed a signal to both cutting coils that is monophonic, but the right channel is 180 degrees out of phase with the left... Would not the resultant groove be strictly hill and dale?

If the exact same signal is given to both left and right coil then yes, the resulting groove is just hill and dale.

However, in the real world, rarely does left channel match the right. That will cause both vertical and horizontal movement of the cutting stylus.

There is a superb animation on Souri's site that explains this.

Scroll down the page to where it shows a 45/45 stereo cutterhead cutting a stereo groove.
http://www.vinylrecorder.com/stereo.html

Precisely the animation I was thinking of when I posed the question ('t'was not Greybeard, fwiw). So, the stereo cutting is indeed a combination of engraving and impressing. I like the different ways of achieving this. The Neumann head has the coils at 45 degree angles and the Ortofon has them perpendicular to the horizontal, but pushing against a rocker which translates their motion to diagonal - _unless_ the signal is correlated... (;


Cheers,
Andrew

[markrob]

Other than surface noise characteristics, the playback stylus may not know the difference between a vertical-cut hill and dale record and one which is, technically, impressed (without removal of substrate).

Andrew

Thats not true. The groove geometry of an embosed (or impressed as you would like to call it) recording is much different than a cut groove. The cut groove maintains a V shape, while the embossed groove is U shaped. This has implications during playback. The embossed recording has high frequency losses (not present with cut recordings) when played back due tracing distortion created by the U shaped geometry. If you are interested, PM me with you email and I'll send you a paper on the subject.

You seem to be convinced that stereo cutting is a hybrid. I don't belive this is the case. If you use a single point cutting tool on a metal lathe and advance the tool into the work, you are still removing material. There may be some intial deformation that ocurs due the the finite radius of the tool tip, but ultimately the process is subtractive.

Mark

[greybeard]

@serif: please do not say "So, the stereo cutting is indeed a combination of engraving and impressing. I like the different ways of achieving this."
The fact is, material is removed in two directions that are at right angles to each other (mostly called "perpendicular"). The movements are continuous, so the chip, swarf, thread comes off in a nice continuous string with one right-angled corner corresponding to the tip of the cutting stylus. If you examine that thread (microscope required) you will find waviness (modulation) on both sides, and on the top you see the variable width that you would see on a record when looked at from above. There is no exception to this! If one channel were embossed, then there would be no chip, swarf or thread to show an impression - it all goes into the record material when you emboss.

What you call a "correlated signal" means that they are in phase. A previous question concerned 180 degrees out of phase giving vertical mono = hill-and-dale. 180 degrees out phase is the same as saying "it has a minus sign in front of it", so it is subtraction. But, someone will say, "you can subtract the left from the right or the right from the left, what is the difference?" The difference is in the phase of the vertical signal obtained: the two situations will provide 180 degrees phase difference between the engraved signals. In other words, where one digs in, the other rises to the surface (both from the reference groove depth).

Opcode66 said: "in the real world, rarely does left channel match the right". Yes, this is very important, and this is the first source of crosstalk. The second is channel separation in the pickup. Lots of worms! Cans of them.

[mossboss]

Greybeard
I would have also thought that you would have also pointed out that this animation would also have provided a very good visual answer for these people who have not managed to grasp the concept of acceleration limiting
I needed some help on this The animation is quite timely by the way
Imagine the cutting stulus driven down and pulled back up agin at a high velocity One would finish up with a very sharp and shallow V
It is slowed down so it does the correct shape so as to provide the correct radius at the bottom of the groove
That is why the acceleration limiter is there
Why it is limited to a certain level as well as the fact that it is not a de esser a high end limiter or whatever else it has been called here
The posting up of the maths behind will have to wait for me to put up the maths I am having issues loading it up here but it will be done asap
Once again a very concsise right to the point answer from you on the other points here
Keep it up
Cheers

[Serif]

Hi Mark and Greybeard,

I appreciate your describing the fact that material is removed with cutting and not with traditional disc "embossing." However, my observation of similitude between them is that with both actions (vertical cuts and blunt impressions), altitude is lowered and restored to the disk surface in a analog modulation to the input signal.

It still seems to me that the hybrid _motion_ of stereo cutting is one of engraving and impressing, even though the _action_ of the vertical stylus motion in stereo mastering involves the _cutting away_ of the unwanted height of the disk surface (rather than its periodic compression).

Although there are practical differences between a bluntly impressed hill and dale groove and a sharply cut hill and dale groove, both are hill and dale. This is the extent of the connection I am trying to describe. Nevertheless, I'd love to read more on "embossing" and/or vertical cutting.
(Figures that the blunt instrument is not as hi fi as the sharp one. (; )

andrew@serifsound.com


Thanks,
Andrew