Confused: Cutting angle

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mischmerz
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Confused: Cutting angle

Post: # 40819Unread post mischmerz
Sun Feb 21, 2016 9:25 pm

I usually cut trying to keep a perfect 0 degree angle. However - some people suggest a slight angle, usually 3 or 5 degrees. I just don't know in which direction. So - should the stylus lean in the direction of the rotating disc or against it ?
cutangle.png
What would be the right direction? A or C ? And why?

Thanks

Michaela
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rsimms3
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Re: Confused: Cutting angle

Post: # 40820Unread post rsimms3
Sun Feb 21, 2016 9:30 pm

My understanding was for lacquer it's A in your picture but I've seen folks cut plastic like figure C. If I've been doing it wrong (I shoot for 0 as well) I'm glad you asked! :D

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Re: Confused: Cutting angle

Post: # 40829Unread post Greg Reierson
Mon Feb 22, 2016 10:16 am

It may be different for other systems/media but for master lacquers it's definitely B. The Neumann manual gives essential zero tolerance for cutting angle.
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Re: Confused: Cutting angle

Post: # 40880Unread post opcode66
Thu Feb 25, 2016 8:44 am

I think you mean C for Neumann. The stylus is 8 degress lean from perpendicular. I can scan the section of the manual that describes the angle. It is small. But, not perpendicular like B.

For Presto and RCA and many other Mono Cutterheads it is A.
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Re: Confused: Cutting angle

Post: # 40885Unread post Greg Reierson
Thu Feb 25, 2016 9:12 am

From the manual:
Stylus Angle.JPG
I was wrong about the tolerance but vertical is specified.
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Re: Confused: Cutting angle

Post: # 40886Unread post mischmerz
Thu Feb 25, 2016 10:20 am

Stroking? Digging?

mm.

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Re: Confused: Cutting angle

Post: # 40887Unread post Greg Reierson
Thu Feb 25, 2016 10:28 am

A would be stroking. C would be digging.
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Re: Confused: Cutting angle

Post: # 40894Unread post opcode66
Thu Feb 25, 2016 6:45 pm

Hmmm... That is odd. Here's why. The design of the SX74 head incorporates an angle when mounted properly and the tilting suspension plate is flush with the suspension itself. The angle it implements is forward, not back. Check it out for yourself on the lathe. Drop the head outside the platter and note the natural angle that is part of the design of the back mount. The angle that is implemented is C when the face plate is flush. I am reading the stroking not digging part. But, it is inconsistent with the actual design of the head. Most videos I've seen of places like Abbey Road cutting discs, when they zoom in on the cutterhead, it is leaning forward.

To cause the cutterhead to make the stylus travel with an angle like A you would have to adjust the suspension spring or depth knob to counteract the natural angle of the SX cutterhead mount, in addition to providing the angle for A. That would certainly cause the tilting face plate to no longer be flush with the face of the suspension box. That is what makes me feel this part of the manual wasn't translated correctly. And, it wouldn't be the only example of misleading translations or mistakes in their documentation....

There is no way to achieve A and have the tilting plate be flush due to the angle of the mount.
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Re: Confused: Cutting angle

Post: # 40896Unread post mischmerz
Thu Feb 25, 2016 8:40 pm

Greg Reierson wrote:A would be stroking. C would be digging.
Thanks Greg.

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Re: Confused: Cutting angle

Post: # 40897Unread post Greg Reierson
Thu Feb 25, 2016 9:14 pm

I see what you mean. It's hard to get a good side view but I'll take a look at the lathe tomorrow.
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Re: Confused: Cutting angle

Post: # 40904Unread post jesusfwrl
Fri Feb 26, 2016 5:50 am

This is one of the most often confused subjects in disk cutting.

The answer is surprisingly simple, but it takes a lot of digging into old books to put all the puzzle pieces together.

In the days before stereo, the lateral modulation became the most commonly accepted disk recording format.
The recommendation at the time was that the stylus (and mono head) was meant to be near vertical, forming an angle of around 90 degrees with the record surface. The official line for most manufacturers was an exact 90 degrees, but most of the manuals stated that some people tend to prefer a slight leading or lugging angle of a few degrees. One manual even stated that laboratory tests have shown better results with a slight angle compared to totally vertical. Don't forget that these where the days of monophonic disks and pure lateral groove modulation. Standardisation was still a long way from being achieved in any reasonable way and different record labels even used different pre-emphasis time constants. Styli had long shanks and most heads (that I've seen at least) had the stylus mounted parallel to the head. The lathes of the time all had some form of angle of cut adjustment, and different adaptors where used for mounting different heads, to allow the user to achieve the desired geometry using a variety of different heads, which were often used interchangeably on the same lathe.
Any difference between cutting angle and reproduction angle in a mono disk with pure lateral groove modulation would affect the precision with which the reproduction stylus tracks the groove, but a few degrees one way or another would not make a considerable difference, especially when taking into account the inherent distortions of the magnetic cutterheads of the time, long shank stylus resonances and primitive reproduction equipment.

Then came the stereo disk.
The stereo disk involves a combination of vertical and lateral modulation to store stereophonic information in a single groove. The modern stereo disk does this on a 45 /45 degree plane. So, monophonic information would still result in pure lateral modulation in the groove while 180 degree out of phase information between the two channels would result in pure vertical modulation. In the vertical plane, a matching angle of cut with an angle of reproduction (known as a vertical tracking angle), becomes extremely important for accurate distortion free reproduction.
So, standardisation soon came into effect and the decision was stereo disks should be cut and reproduced at a "digging angle" of 15 degrees. That is the angle direction shown in C of the original post.
So, not only is the record meant to be cut at that angle, but it is also meant to be reproduced in that angle, to avoid distortion.
The distortion during pure lateral modulation would be far less severe than the distortion during pure vertical modulation, so any angle mismatch would be most severe on the difference channel. This is how an angle mismatch produces distortion. The later Neumann lathes, designed for stereo disk recording, were all designed to the 15 degree specification.

To complicate matters further though, the stylus is no longer vertical to the head plane. The head is also no longer parallel to the record surface. The final angle of cut on a Neumann VMS 70 is determined by the head tilt together with the stylus tilt as it is mounted in the torque tube. The suspension is meant to be vertical to the record surface. The moving part of the suspension is meant to be dead flush with the box, as stated in the manual. The head mount itself introduces a head tilt of 8 degrees. The head is leaning forward, forming an angle of 8 degrees with the record surface. The stylus is mounted at an angle of around 7 degrees less than vertical (that would be around 83 degrees) on the torque tube. The head tilt of 8 degrees plus the stylus mounting angle of a further 7 degrees results in a total angle of cut of 15 degrees, in the direction of C. This is a digging or leading angle. This is also similar to the angle used with a chisel in wood working.
This system is also applied to the Vinylium SC99 and the Flokason Caruso heads, as well as the Neumann SX68 and SX74, to the best of my knowledge.

Manufacturers of reproduction cartridges were also generally following this standard and the better tone arms allow for precise tracking angle adjustment to make it possible for such tone arms to be easily mounted on a variety of turntables and the vertical tracking angle to be adjusted on each turntable.
Scully lathes with Westrex head also used the same 15 degree cutting angle and I assume that Orthophon did the same.

So, the standard is 15 degrees, if you have an original Neumann lathe with the suspension adjusted according to the manual, you will be getting a 15 degree angle of cut. This is the one to aim for with any system intended for stereo disk recording /reproduction. Some people suggest that different angle of cut might produce better sounding cuts, but this is a complicated subjects and it deviates from the standard.
The less stereophonic information your cut contains (the closer it is to pure lateral modulation), the more you can get away with angle mismatches. While a different angle could produce a quieter cut on some material or a different sound, it would still have to balance out with the distortion on the vertical plane produced by the use of a different angle.

To offer a more specific answer to Michaela, you should ideally be aiming for a 15 degree angle in the direction of C. If you are only cutting mono records, deviating from this angle is not as severe as it would be if you would be cutting stereo disks. If you are cutting 78s to be played on standard groove reproducers of the old days, then close to 0 degrees is a far better bet, as that was the standard of the time. However, if you are using a modern turntable and cartridge fitted with a standard groove stylus, the cartridge is most likely designed for 15 degrees. But it won't probably matter much for pure lateral.

Having said that, I also firmly believe that a science/art should be defined by the people who are currently practising it and not by their grandfathers. So, if there's a lot of lathetrolls who strongly believe that a different cutting angle or a deviating from the standard RIAA curve would be a better approach, then we should hold a lathetrolls symposium to discuss such opinions and define new standards. Do not forget that for new standards to be successful, the cartridge manufacturers would need to follow along and the world at large must be wiling to adopt the changes.


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Re: Confused: Cutting angle

Post: # 40907Unread post dubcutter89
Fri Feb 26, 2016 6:42 am

The head tilt of 8 degrees plus the stylus mounting angle of a further 7 degrees results in a total angle of cut of 15 degrees, in the direction of C.
that is not really true. the stylus is mounted at an angle to compensate for head vta.
the idea is that the cutterheads drive mechanism (=drive coil + linkage) is modulating the groove with a given tracking angle (15 degree +- whatever) but the stylus is at a right angle to the disk. BTW, the angle at which the head (drive) is mounted does NOT correlate with the VTA!!! There are lots of papers etc. about that. Including modulation on rotational basis, lacquer spring back etc. science at its best by engineers that knew what they were doing!

At the end of the day I would recommend to mount the Neumann head as they specified, mount all other heads the way you feel comfortable and feel the least distortion. Who really knows what VTA disks were cut, will be cut, and what VTA the cheapo worn out playback of somebody has..

Here is a snippet from Neumann folks:

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Re: Confused: Cutting angle

Post: # 40908Unread post jesusfwrl
Fri Feb 26, 2016 7:19 am

Yes, I do not disagree.
I probably over simplified my drawing a bit, but the general point is the same regarding the VTA. The mechanism behind this is indeed more complicated and on the reproduction side I did not draw at all the pivot point. My intention was to keep it as simple as possible.
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Re: Confused: Cutting angle

Post: # 40915Unread post tragwag
Fri Feb 26, 2016 10:17 am

just wanted to say I learned a lot from this thread, thanks all for the very learned discussion
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Re: Confused: Cutting angle

Post: # 40919Unread post Greg Reierson
Fri Feb 26, 2016 12:48 pm

I took a look at my cutting stylus in the "down" position as well as a head out of the system and I think the docs I have must be either worded incorrectly or just out of date / for the wrong system. There definitely is a pronounced stylus angle corresponding to C above.

The puzzling thing is that I know many in the audiophile world stress over the exact angle of the pickup stylus. My friend Wally Malewicz http://veteranhifi.se/WVC/index_wally.html is adamant about a 92° angle (which had been influencing my understanding of the cutting angle) but doesn't seem to match the cutting angle. I would invite him to this discussion but maybe I'll talk to him off-line first.

In the mean time, this is what some in the audio world recommend WRT VTA:

http://www.analogplanet.com/images/512MFVTA_article.pdf

http://www.analogplanet.com/content/how-use-usb-digital-microscope-set-92-degree-stylus-rake-angle-sra#Vc3mFUZFYuypZM3U.97

We can only hope that the recommended pickup alignment matches the records we cut. But if we're cutting at 75° and they're playing back at 92°...

And if you really want to dive into a rabbit hole:

"Three FM Methods for Measuring Tracking Angles of Phono Pickups," by White, James V. and Arthur J. Gust, Jour. of the Audio Eng. Soc, Vol. 27, No. 4, April, 1979

It can be found in the JAES Disk Recording Anthology, Vol 2, page 543.

It is very detailed, to say the least... Deep in the article they observe that the CBS STR-112 test record was cut at 16.5° (90-16.5=73.5°). It may not be a wild guess (based on what I have read on the topic in this thread and my own experience with setting up the angle of the cutting head) that the intended angle was 15° (75°) and 16.5° (73.5°) was simply an in-the-field deviation of the calibration of the cutting system. I am not aware of a jig to set the exact cutting angle beyond the design of the system and visual alignment of the suspension plate.

Anyway, it's looking to me like C is the correct answer.
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Re: Confused: Cutting angle

Post: # 40920Unread post Sillitoe
Fri Feb 26, 2016 1:02 pm

Greg Reierson wrote: I am not aware of a jig to set the exact cutting angle beyond the design of the system and visual alignment of the suspension plate.
A goniometer adjustment stage for the head mount, but then you also need to have precision adjustment for the suspension box in Y and Z axis.

I set this up with my suspension spring mounted on a micrometer head, the other end of the spring connects to the front of the pivot bar at an angle.
I also use a locking torque hinge head mount for coarse head angle adjustment.

Trying to get it to sound real nice, early days (don't have a nice playback system yet) but the precision mechanism works very well and is adjustable on the fly.

Cheers
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Re: Confused: Cutting angle

Post: # 40929Unread post Sillitoe
Fri Feb 26, 2016 9:58 pm

To elaborate a little in an attempt to make it clear (hopefully :D )

I fully agree with everything dubcutter89 said.

For Neumann- I assume that the automatic groove depth functioning would be adversely affected if you adjust the front panel of the suspension to anything other than the setting specified by the manufacturer.

This has been my experience while cobbling together my little system.

Cheers
James

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Re: Confused: Cutting angle

Post: # 40939Unread post jesusfwrl
Sat Feb 27, 2016 7:34 am

I should point out more clearly that my drawing above represents a very theoretical picture of how cutting and reproduction angles work. It only takes into account a purely theoretical situation where the cutting stylus moves vertically in a straight line, without considering the effect of any means of support in a real world cutterhead, which would make things a lot more complicated. It also cuts into a theoretical medium without the effects of real blanks. The theoretical reproduction stylus at 90 degrees also appears to be moving purely vertically in a straight line, again not taking into account the effects of the cantilever/suspension and other factors present in a real life cartridge. The 75 degree reproduction system in 3 shows a crude representation of a theoretical cantilever which should ideally have a pivot point somewhere between the stylus and the magnet.

This drawing was only intended to demonstrate how distortion is produced by angle mismatches, in an extremely simplified form.

In a real life system, there are far more factors affecting the angle at which a disk is cut and the VTA during reproduction.
For a start the cutting stylus does not usually move vertically in a straight line.
On cutterhead designs incorporating a torque tube such as the Neumann SX68/SX74, Vinylium SC99, Caruso and so on, vertical motion of the stylus actually scribes an arc instead of a straight line. Moreover, lacquer has spring back due to the nature of the material, long shank styli tend to bend, and so on...

On the reproduction side, reproduction styli also do not track vertically in a straight line, there is usually a cantilever with a suspension and pivot point which also guide the reproduction stylus into an arc and it also would be prone to bending. Tracking weight affects the resting point of the mechanism and different manufacturers design vastly different cartridges. Reproduction VTA cannot be estimated easily just by looking at the angle with which the stylus itself rides in the groove, or the angle of the cantilever, or the angle of the cartridge body. One needs to be aware of the internal working of the cartridge to be able to mathematically estimate the true VTA of the system.
I would assume that very few people are intense enough to really take all this into account and even fewer home listeners would really care about such an amount of precision. So, adjusting VTA by ear, might get you somewhere close, and adjusting it with a test record and scope will get you even closer.

A 92 degree angle would make me think of the angle at which the stylus would ride in the groove, more than the actual VTA. On that particular system, a 92 degree stylus angle might translate into a real 15 degree VTA.

The 16.5 degrees of the test record you mentioned could definitely be a result of calibration tolerances, or it could even be intentional to compensate for what might happen to the lacquer in the time it takes before plating, during the process of plating, and what the grooves will actually look like on the pressed record. Or it could be a lack of accurate compensation for all these effects.
In either case a 1.5 degree mismatch with actual music on a real world system would be pretty damn good. I would imagine that the average system does a lot worse than that.

Still, that does not mean that we should be less careful about following the current standard when cutting. Not following it would just make matters worse. For instance, If I cut something at a different angle to match my grandmas entry level turntable stock setup, it might not play well on my uncles entry level turntable and also wouldn't play well on an audiophile system which the owner took great pains in calibrating.

Personally, my aim is to try to be as close as possible to the ideal case, while maintaining compatibility to the extend possible with a variety of badly calibrated systems. The AES Disk Recording Anthology is a great place to start for anyone who would like to gain a better understanding of the science behind all this.
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Re: Confused: Cutting angle

Post: # 40942Unread post Sillitoe
Sat Feb 27, 2016 9:08 am

Great interview here from Andreas Lubich of Dubplates and Mastering Berlin.
At about 22min he talks about test cuts and playback, no point testing the playback of a club tune on the highest-end tonearm/cart setup, or playing back a Jazz cut on a 1200 with reversed counterweight and anti-skate setup for the club.

Hey Jesus, new standards (RIAAA etc) could be an absolutely amazing commercial venture for the audiophile market! :lol: :lol: :lol:

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Re: Confused: Cutting angle

Post: # 40948Unread post jesusfwrl
Sat Feb 27, 2016 12:29 pm

Sillitoe wrote: Hey Jesus, new standards (RIAAA etc) could be an absolutely amazing commercial venture for the audiophile market! :lol: :lol: :lol:
Yes, especially if we re-define the disk medium as a 16" disk running at 78 rpm with a custom EQ curve to match! :twisted:
Then, not only could one sell 16" turntables with integrated high-end phono stages with switchable equalisations to audiophiles with enough of a budget for it, but you can also sell custom cutting electronics to cutting engineers wanting to enter this market... (dollar signs rolling in eyes?)
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