The Finish Line for your Phono Cartridge- Stylus Wear by Mike Bodell

Only if they are expecting the sound to be louder while it isn´t.

 

Well its easy enough to check.

 

Let's pull out the old car analogy for this one- the stylus, worn or new, is the contact patch with the record surface- a fresh stylus is going to have better contact with the grooves and navigate them--Peter L. speaks about 'jitter'-- that the stylus is shuddering, and being bounced around, not staying in continuous contact; since the cartridge in question is a 'cantilever-less' design, that's not as big a part of the equation. Entirely speculation on my part, but one possible explanation for why the retip sounds louder.

 

Ahh, was that a Decca London re-tip? As I understand, re-tipping those is more involved than with a standard cartridge. The whole damping/cantilever/support cord is removed and replaced, so indeed this could make a big difference.

 

Yes, the same paratrace type stylus that came on it originally. Mr. Wright did say besides the re-tip other adjustments were involved, such as a "re-calibration" of the suspension, which may be responsible for the apparent increased output.

My London Reference cartridge does not have the typical cantilever of most of the rest of the cartridge types. The stylus is attached to a pole/'cantilever' which itself is attached to the cartridge by the aforementioned suspension, which is electrically sensitive to minute vibrations from the record in a process known as 'positive-scanning', almost unique among cartridges. The output is a robust 5 mv, which I use through the MM section of my Tavish Adagio phono stage.

 

Yes indeed.

 

A better explanation than mine....

 

Makes sense why the performance improved. You probably got an "upgrade" to whatever new support configuration they're using today.

The London cartridges are really interesting in design. They don't directly read the L and R channels, instead reading the vertical (stereo) and horizontal (mono) channels, then matrixing the outputs into a stereo L/R pair. I think it's a brilliant concept as it practically guarantees a stable central/mono image with less sensitivity to cartridge internal alignments, etc. Do any other cartridges use this principle of horizontal/vertical matrixing for stereo?

 

Maybe 'shearing' isn't the most apt descriptor for what's happening....maybe 'bludgeon' would be better. End result is essentially the same.

 

Not trying to hijack the thread, but I've wondered for 20 years or so (ever since being introduced to the manner signal is cut to a stereo record and the very similar concept of mid-side recording) why there's not been any apparent attempt to use mid-side for playback - you'd be pre-configured for true mono compatibility, you'd have the ability to control stereo width to suit the needs of playback, and it seems like you'd have the ability for a much larger sweet spot - by doing this exact thing. The hangup seems to be the need to re-matrix the signal at some point - a mid-side reproduction system seems like it would need three speakers (center mono and one for each side, with that side pair wired out of phase with each other), which is at least half again more complicated than the usual stereo pair c. 1957.

At any rate, that's a very interesting tidbit about the London Deccas I'd never heard before (as this cart's well out of my price range, system capabilities, hearing capabilities, etc., I'd never really looked too closely at the details), and I'd be interested to know if any other carts use that approach.

Also, this thread gets my vote for 'Thread of the Year' - @Ray Parkhurst , thanks for taking the time to run the test and post reports!

 

The stereo matrixing is actually pretty easy, and is done inside the cartridge. Key is that there are two matched coils for the vertical signal, so that they can be wired opposite polarities with the horizontal coil to produce the L and R stereo signals, like this:



The image above is from the following stereophile article which explains the priniciples and also has a diagram of the coil and cantilever physical arrangement:

Decca Mark V phono cartridge

 

I've heard that Ikeda from Japan produces something similar, and a few companies tried their hand at this technology in the '70s and maybe later. I found this brief informal outline of this rare cartridge technology...Mono and Stereo High-End Audio Magazine: POSITIVE SCANNING CARTRIDGE

Ray, are you going to continue your stylus/record wear experiment? It would be interesting.

 

I am not sure yet.

 

The AT Art1000 has coils directly above the stylus chip....closeup images make it look as though the cantilever is wearing reading glasses to get a better view of the groove lol. One other example of positive scanning everyone should be familiar with....the ubiquitous ceramic cartridge!

Apt Holman made a preamp that divided the signal into sum/difference that could then be manipulated to enhance the stereo spread or shrink the stage down to mono. It was on ok preamp, but had a lot of controls that probably degraded the signal. Monaural cartridges based on 2-channel coil arrangements use summing to cancel the difference signals leaving only the summed output, but that's not quite the same thing.

 

Wasn't the Neumann (rare as hen's teeth) a cantilever-less design? Ditto the Tzar, which was a copy of the Neumann? At least there's support for the Decca (now London).

 

The manner stereo is cut is the same manner in which it is played back - 45 degree angles. There is no "mono" signal, only channel crosstalk from playback imprecision.

 

Well, yes, but a center channel signal is still cut laterally, just like a mono record. This was a deliberate engineering choice as it provided not only backwards compatibility, but also the reduced groove wear that is the reason lateral cut records became standard.

Which brings to mind another question: which direction the stylus moves is the most responsible for stylus wear? 45/45 would seem to be the best compromise for a stereo record, but does that also average out the wear forces acting on both it and the stylus? I guess the question is, given the same stereo recording, would a mono pressing played back with the identical stylus, extend the stylus life over the stereo pressing, or reduce it?

 

I'm not a fan of such blanket statements, especially when they are very likely incorrect. Some records are cut similarly to the way the Decca London cartridges play back the signal. By my understanding, some or all Decca London records were cut this way, and supposedly some other EU record labels also use this technique.

 

Let's figure it out.

A stylus sits in a 45 degree-per-side groove, and applies 0.707x the tracking force to each groove face, always at a (near) 45 degree angle. The forces can change in magnitude, but not in direction.



If the stylus and cantilever is considered to have no mass and no spring constant, then this lateral pressure is constant regardless of the modulation.

Let's say that the groove is modulated side-to-side, as mono, but we have a real stylus reluctant to move and stop moving. Any increase in force on one face corresponds to a decrease in force on the other side, so on average there is still the same total friction force as silence.

Can we contrast that to a single-channel modulation, when just one groove face is moving at a 45 degree angle? Here too, we have part of the waveform giving more friction when the groove lifts, while on the second half of the waveform we get less friction on that face as the groove descends under the stylus - an average of the same friction. Similar with out-of-phase up and down - alternating frictions that add up to the same average.

We can also think about the cartridge suspension and it's springy-ness and the motor's resistance to movement: most suspensions are like a donut around the cantilever, and have no preference in direction as they are made uniformly. Likewise, a movement in any direction generates the same total coil current (combining the 90 degree angled coils), so the pickup shouldn't cause a difference, either.

(However this is a simplification that misses that the groove has a third dimension and one more source of friction - the future waveform that touches the stylus tip earlier because of the curvature of the groove. This is a new friction due to modulation, and is the one that causes more friction and skating during loud passages. Additionally, the vinyl deforms under increasing pressure in the waveform cycle, perhaps non-linearly, turning the weight and rotational energy into friction and heat.)

You remove all the up-and-down content and you get a quieter signal, so yes, a quieter record could mean less stylus wear. A mono record (with the L-R content removed) wouldn't be cut the same, though - we can cut a hotter mono record, without fear of modulating the stylus contact point higher than the top of the disc face, nor need to avoid movements that might otherwise eject the stylus into the adjacent groove.

We want louder records when possible; stylus wear isn't the concern.

The Neumann ZS 90/45 cutterhead (1958) is one of the few that would do so, when combined with a stereo differentiator to drive the up-down coil, but it was also engineered this way because stereo still had the possibility of being recorded with lateral mono=left, up/down=right. It should still produce a stereo or mono disc with the same geometry, just as a now-standard 45 degree lathe will still produce a mono disc (and in fact the stereo lathe cancels some mono coil distortion mechanisms).

 

GREAT article, thank you! I totally reframed my thoughts on buying the next cart, for me, the key will be thinking long-term, i.e. over the next 5-10 years, if I need to change out my tip every 1-2 years, what is the best cart to buy now?

 

Depends on your budget.

 

Some people like Sound Smith, not only for sound (I've known Peter a pretty long time, but don't know that I have ever heard his cartridges) but the relatively low cost of retipping. He did a true retip for me of an Airtight Supreme, just replacing the stylus, not the entire cantilever plus stylus.
I buy cartridges based on sound, not on cost of replacement, though the top tier cartridges have gotten to be nutty money; I'm not against third party retips-- I know that it is never the 'same' but if the stylus is worn and you aren't going to spend for a factory re-do (which can sometimes be costly), you've got something that is pretty much worthless. So a third party retip at reasonable cost makes sense to me. I think a lot of the "high end" people move on to a "better" cartridge rather than spend the money for a factory retip (or get some trade in allowance if available). I have some cartridges that justify factory rebuild despite the cost.
My main take away from the article-- for which Mike Bodell (@BendBound) deserves all the credit- is to monitor usage using a tally counter so you aren't guessing, and to be sensitive to changes in performance. The experiment that Ray Parkhurst (@Ray Parkhurst ) did using a light tracking force cartridge running continuously for hundreds of hours with intervals to examine stylus wear (Ray's work is posted throughout the later part of this thread) showed that low tracking force was one factor. The cartridges I've been using typically track just under 2 grams. Clean records help, though Ray didn't really try to "measure" the effect of the surface contamination on wear (nor did he analyze what that contamination consisted of-- one of the issues that was banging around the subject was whether any "diamond dust" from the stylus contributed to increased wear. But even in the absence of that information, it only makes sense to keep the records clean). I'm far more attuned to what is going on in the stylus interface with the record surface as a result of Mike's article and it was an education for me, both to help him publish and to be involved in this thread, which had some important insights.

 

Anything new?
Did you ever make any soundclips of the worn stylus and grooves?

 

@Bill Hart Agreed on the takeaways, I'm ordering a clicker/counter and will clean my records more religiously...

 

I have not had time to read all of this long and interesting thread yet, but I intend to. However, I noticed that in the first few pages, cuts, applied to stylus diamonds in order to produce line contact, were being discussed as if they were facets produced by wear. Was this error corrected, or have I misunderstood something?

The idea that facets produced by wear would have sharp edges which damage records seems very unintuitive to me. It seems that this could only happen if all your records were silent, in which case it wouldn't matter. Hot passages in the vinyl will surely wear the edge of the worn facet making its edges fairly benign, and probably no worse than a fresh micro-line diamond in terms of groove damage, if not audible distortion.

Please correct my ignorance...