Mono Cartridge Question

I have got to agree with Dave @intactaudio. I think a conical stylus is simply not appropriate for playing back ANY groove cut by a cutting stylus made in the last 75 years (and perhaps more). If the playback stylus is not a facsimile of the cutting stylus - or if it is misaligned - it will NOT take the same path through the groove as the path used to cut the groove in the first place.

This is NOT to say a conical stylus won’t sound good! I am only saying you are giving up information in the groove and adding distortion (including, but not limited to, some second order harmonic which could be pleasing, but certainly not accurate.)

I posted an animation on our website to show how we simulated in finite element analysis software a 25um conical stylus tracing a 10kHz groove at 60mm playing radius. You can clearly see the vertical excursion of the stylus on the right side. The left side shows that the basins of the undulations don’t even get touched by the stylus. The stylus kind of skips from peak to peak. This happens to a lesser degree all across the record surface and certainly at lower frequencies than 10kHz. We choose a high frequency for this animation so it would be easy to visualize. If this were a mis-aligned fine line contact stylus, it would have even MORE vertical excursion (in a perfectly horizontally modulated groove, mind you) but it would at least reach down into the basins all the way.

Now, if you have a mono cartridge with a conical stylus and that cartridge does NOT allow vertical freedom of the cantilever, what do you think is happening to your grooves over time??? Not good, IMO. Dave may have already alluded to this issue.

By the way, @intactaudio, your silvered auto-formers are unbelievably excellent. I’ve turned many people on to them! I’ll use nothing else!

Cheers,

J.R. Boisclair

@goofyfoot, this induced errant vertical excursion can be easily calculated mathematically if you are comfortable with numbers. A conical stylus (and, to a lesser degree an elliptical stylus) will exhibit this induced errant vertical excursion to make its way through the groove to greater and lesser degrees depending upon record velocity, frequency and playing radius. This "pinch effect" has been known for decades and has been written about in the scientific journals in the 50s and 60s. What few cartridge designers fully appreciate is that the perturbations in the groove that ultimately result in an audible signal can be measured CONSERVATIVELY in the low triple digit nanometer range. The stylus in the animation I shared above has this errant vertical excursion in the single digit micron range. The high frequency portion of a frequency sweep on a test record has a horizontal perturbation around 3 microns. That's all!

I have analyzed hundreds of cartridges by nearly 50 manufacturers and can attest that there are VERY few cartridge designers who fully understand the microscopic world their products are meant to navigate. Fewer still who understand why a high fidelity mechanical transcription requires the playback contact points to be not only a genuine facsimile of the cutting contact points but their angles must agree with each other NET of lacquer spring back.

Hello @fortheloveof,

You asked, "What do you think then of the DaVa field coil cartridge that features a conical stylus? Many, including the few on this forum who don't trash a cartridge they have never heard, claim that the DaVa is one of the worlds' best. Do you think these claims are simply emanating from a love of colouration and that the DaVa cannot by your definition be anywhere near a great cartridge?"

For the record: I have not heard this cartridge, but would certainly like to. 

NO...I am not saying that people love this cartridge because of any colorations, whether such colorations are real or imagined.

What I am saying is that if ANY cartridge has a conical stylus, it CANNOT possibly extract everything there is to get from the groove. This is a metrological certainty that can be calculated and proven in at least four ways I can imagine (one mathematical, two by software and one by microscopy). 

So, if you think that this cartridge is great now...I can only imagine how great it would sound with a playback stylus that was a facsimile of the cutting stylus that was used to create the very groove is it was meant to transcribe (as long as that stylus has been properly aligned to do so, of course - just because you have a fine-line contact stylus doesn't mean you will realize its benefits without some work!)

Now, if someone - ANYONE - has heard two of the same cartridge design but one with a conical and one with a fine line stylus and claimed it sounds better with a conical than a fine line, I'd respond by saying all the variables in the test between the two iterations of the same cartridge have not been fully controlled for, making the experiment one with a negative value. Either that, OR, the listener values an extra bit of lush warmth (and not much more, at that, as the second/third harmonic content generated by conicals aren't very significant) OVER the improvements in focus, dynamics, high frequency extension, inner detail, imaging and soundstaging that a properly aligned fine line contact stylus offers.

I have no doubt it is a stellar cartridge and I want one, but I'll certainly take mine with a fine line contact edge, please!!! 😁

Hi @goofyfoot 

You said, 'The size of the stylus is a factor here too. A larger stylus being exponentially more detrimental than a smaller stylus"

I don't know why this might be the case, but I am not surprised if there is a good reason for it. We have spend little time studying conical stylus behavior, putting our efforts on fine-line profiles predominantly. The one thing I have found to be certain in the last three years of diving very deep into the relationship between the stylus and the groove is that the more I learn about it, the more I realize how much I don't know!  If you can please explain why this would be so to me, I'd be appreciative of it

To date, the only thing I see out of our research is that a larger conical stylus (vs. a smaller conical stylus) differs on where it will contact the groove wall. Larger conical styli track higher on the wall and smaller down further. This is why when some people change to a different cartridge and note how much quieter or louder the groove noise is, they mistakenly attribute the change to the cartridge being better or worse when it can more often be explained by the change in stylus geometry and the elevation of the contact point in the groove. If you've been causing damage to a groove wall and happened to have been using a large contact radius and then changed to a smaller contact radius you might experience a quieter listening experience. All you've done in such a case is ride below the previously made groove damage, so you're not hearing it any longer. This can happen when you realign a fine line contact stylus as well. When properly aligned, such styli will ride at their maximum elevation in the groove. 

@goofyfoot, it is definitely the opposite from what you were told. A larger object will not fit as far down into a 90 degree groove versus a smaller object of the same basic profile.

The degree to which they differ in their elevation on that groove wall can also be easily calculated. A 1mil (25.4 micron) diameter conical will ride about half way down a nominally cut unmodulated groove (50 micron width). A 0.6 mil (15.2 micron) conical will ride about 20% lower. That isn’t small change.

The contact area of both sizes are VERY similar. Why? Because the point of groove wall contact is on the spherical portion of the stylus. (Technically speaking, points of contact with a sphere are infinitely small but in practice you must consider groove deflection.)

Using a spheroid contact area is VERY important to allow for tolerance errors on the mounting of the stylus to the cantilever on the azimuth axis. This is also why fine line styli have a major radius. This is also why proper azimuth alignment has NOTHING to do with the stylus alignment in the groove regardless of stylus profile (up to a point, any way, but that point is usually past 2.5 degrees level headshell and often more)

Now, I would certainly argue that the smaller contact surface area of the stylus to the groove wall, the greater the chance for groove damage because the force is distributed over a smaller area, causing greater groove deformation. This is another advantage of fine line contact styli over conicals and also why a larger conical probably has a slight edge over smaller conicals in avoiding groove damage which is quite the opposite from what you’ve heard.

However, I AM ALWAYS OPEN TO NEW, YET CONFLICTING, INFORMATION. I invite it as it is the only way I’ve been able to help push this industry forward so far.