Mono Cartridge Question

@intactaudio Saying that a conical stylus causes premature wear isn’t an outrages claim but I have no idea about what the groove would look like before and after. This is the first time I’ve heard anyone say as such and while it’s a perfectly plausible statement, is it something to fret over?

@goofyfoot 

To be clear, JR posted about the added vertical movement from a conical in a high frequency purely lateral groove.  I added that in the case of a cartridge with minimal / no vertical compliance this can be a very bad combination.  If this were a situation where the cartridge tracked at 1.5g I wouldn't be as concerned as one that tracks at 4g.

dave

@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.

For those of challenged imagination, look at it this way: a groove wall with lateral deviations will push back against the stylus (yes, that's Newton's first law). The shape of the stylus will affect the direction of force exerted on the stylus, which just a little painless thought about vectors will make obvious. Image pushing your finger in a horizontal direction against a plane inclined at 45° to the vertical. Your force will be equally divided into a lateral and a vertical component, and the inclined plane will move not horizontally, but in a direction 45° above the horizontal. Those vectors will mean that a rounded stylus profile will experience not only lateral pushback, but also some in a vertical direction. That will tend to make the stylus go up and down, just like the chatter on a machine tool. A stylus with a side profile that is more vertical, will experience that force more in the lateral plane and less in the vertical.

None of this will matter more than it does with a stereo record and a stereo cartridge, as long as the mono cartridge has vertical compliance. If you have a mono cartridge that has no vertical compliance, all that vertical force has no suspension to damp it: it must make the whole stylus/cantilever/cartridge move up and down with the resulting hammering in the groove. This seems rather elementary.

Now you might argue this - but what does vertical chatter matter if the groove only contains lateral information? Sure, we can go there. Conical styli used to play mono records for many years in the days when mono cartridges never dreamed of having vertical compliance. Did those records suffer more damage than a mono disc with a non-vertically compliant cartridge? Than a similar cartridge with an elliptical profiled stylus? Or a stereo record with a stereo pickup? I don't know, but I can see the theoretical argument for why this should be so.

This does make me feel more likely to settle on a cartridge that is an adapted stereo design, with its guts rotated 45° and with a modern profiled stylus. That way I'll do no harm if I accidentally put a stereo record under that pickup, and I know I'm theoretically less likely to damage my original mono Parlophone Beatles.

@wallytools Yes, I understand the theoretical principles involved. The size of the stylus is a factor here too. A larger stylus being exponentially more detrimental than a smaller stylus. My stylus is a 0.65 conical and my arm is a 9 inch set for  Baerwald. I'm getting more noise with newer records than with my older records. For me, noise would be significant inside one groove and then it clears up for the remaining LP.