MM vs MI vs MC

[eliash]

I apologize if this has been mentioned earlier. In the US, the popularization of mostly Japanese made MC cartridges happened in the early to mid '70s. [MC were sold earlier, such as the Grado and ESL--that I believe was a rebranded Ortofon SPU--but they were outliers] Much ink was spilt over why the MC was an inherently superior sounding design, when compared to MI or MM. I don't want to get into whether that was really the case, but many thought so.

Reduction in moving mass was one idea, however most MC were relatively low in the compliance department, so the decreased moving mass wasn't going to buy anyone superior 'trackability' (at least in the Shure V15 sense).

Also, at that time line contact shapes were becoming prevalent, a spinoff from the discrete four channel JVC Shibata geometry. But you could get those diamonds in MI and MM, so any sonic improvement attributed to MC wasn't that, either. 'Exotic' cantilever formulations (boron, beryllium, diamond, ruby etc.) could be had in all the multiple designs, too.

An early MC champion, Mitchell Cotter (working through the editorial offices of Peter Aczel), argued that the MC design's less susceptibility to FM distortion secondary to 'axial pumping' or a 'back and forth' displacement of the stylus within the groove, was the key. This was secondary to typical suspension parameters of MC, as opposed to the usual MI/MM cartridge.

A MC cantilever was usually tied from the the back by a small length of 'piano wire', allowing the stylus to move in an up and down and circular motion, following the groove patterns, but not a front to back motion. Alternately, the rubbery suspension of the MI/MM allowed the stylus to move longitudinally, back and forth, in addition to circular groove induced motion. This back and forth movement induced an unintended frequency modulation.

This idea was not something Cotter came up with, but rather pointed back to an article published in the Journal of the Acoustical Society of America by J. Rabinow and E. Codier (Ordinance Development Division, National Bureau of Standards, Washington D.C.), Volume 24, No. 2, March 1952. The paper is hidden behind the Journal's paywall, but can be found on line elsewhere. Also, a freely available digest can be found at Google Docs, NBS Technical New Bulletin, March 1953.

I have scanned that abstract/review below.

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On the other hand, an iron core cross, where the typical MC-coils are wound upon, produces a significant amount of "Barkhausen-effect noise", when iron moves in the strong stationary magnetic field. Easily recognisable when the load on the tip is varied by e .g. the tonearm lift on a still-standing platter (e. g. entry level MC Benz ACE-S).
Sounds like a worn-out car suspension and is caused by magnetic (Weiss'-)domain-borders shifting around in the iron, while the changing field is being picked up by the coils.
Therefore, according to my opinion, when investing in MC, go for the really expensive iron free coil carrier designs, e. g. made from ruby (which of course have the drawback of yielding only limited electrical dynamic range)...MP (moving permalloy; also located in the stationary magnetic field) seems less susceptible to this effect from my experience with Nagaoka´s MP500...
(check out here: https://en.wikipedia.org/wiki/Barkhausen_effect ;

)

 

[anmpr1]

On the other hand, an iron core cross, where the typical MC-coils are wound upon, produces a significant amount of "Barkhausen-effect noise...

The degree that these 'problems' influence what one hears in the living room is a big question. What we hear often results from a combination of imperfections. Also, it is much easier to measure stuff, than it is to hear all the stuff we can measure.

As an addendum, below are images of 1) cutterhead assembly (not sure which model) showing a 'piano wire' tie down similar to the description found in Denon MC cartridge documentation; and 2) a diagram of one of the Shure V15 models, showing a suspension consisting of a rubber grommet, with no provision for a 'tie back' behind the cantilever (although a 'support wire' appears to be connected to the rubber grommet at the pivot point).

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[JP]

The degree that these 'problems' influence what one hears in the living room is a big question. What we hear often results from a combination of imperfections. Also, it is much easier to measure stuff, than it is to hear all the stuff we can measure.

As an addendum, below are images of 1) cutterhead assembly (not sure which model) showing a 'piano wire' tie down similar to the description found in Denon MC cartridge documentation; and 2) a diagram of one of the Shure V15 models, showing a suspension consisting of a rubber grommet, with no provision for a 'tie back' behind the cantilever (although a 'support wire' appears to be connected to the rubber grommet at the pivot point).


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The Neumann cutters (SX-68/74) have the torsion tube mounted to the head block.

The support wire in the Shure diagram is a tie wire that is connected to the yoke, not the elastomer.

 

[eliash]

...here is the Shure (anti-jitter-)wire, soldered to the cart fixture (needs some zooming)...remains of the last millenium VN45MR!

...probable, Jico MR on boron stylus for Shure has one too, all buried in solder (or glue???)...

 

[anmpr1]

The support wire in the Shure diagram is a tie wire that is connected to the yoke, not the elastomer.

I don't exactly know about the torsional forces extant, however an overhead 'support wire' tied to... (hard for me to tell from the diagram)... at the pivot would likely not prevent elimination (or good damping of) longitudinal forces acting upon the diamond/cantilever as it is dragged along by the record groove. At least not like a wire tied to the back of the cantilever assembly. But I'm just thinking it through, and have no data to support that thought. I can say that the men at Shure were heavy into R&D, so maybe they had it covered.

Other than the work of Rabinow and Codier (from the early '50s) I don't know of any other research on the subject. Again, my first encounter with the idea was sourced from Mitchell Cotter, and his discussion twenty five years later.

 

[eliash]

I don't exactly know about the torsional forces extant, however an overhead 'support wire' tied to... (hard for me to tell from the diagram)... at the pivot would likely not prevent elimination (or good damping of) longitudinal forces acting upon the diamond/cantilever as it is dragged along by the record groove. At least not like a wire tied to the back of the cantilever assembly. But I'm just thinking it through, and have no data to support that thought. I can say that the men at Shure were heavy into R&D, so maybe they had it covered.

Other than the work of Rabinow and Codier (from the early '50s) I don't know of any other research on the subject. Again, my first encounter with the idea was sourced from Mitchell Cotter, and his discussion twenty five years later.

...no wire on a brandnew Nagaoka MP500 moving permalloy stylus...this tube, a carrier for a permalloy insert?...or a permalloy tube, which would make sense for moving mass reduction and larger magnetic profile?...

 

[JP]

I don't exactly know about the torsional forces extant, however an overhead 'support wire' tied to... (hard for me to tell from the diagram)... at the pivot would likely not prevent elimination (or good damping of) longitudinal forces acting upon the diamond/cantilever as it is dragged along by the record groove. At least not like a wire tied to the back of the cantilever assembly. But I'm just thinking it through, and have no data to support that thought. I can say that the men at Shure were heavy into R&D, so maybe they had it covered.

Other than the work of Rabinow and Codier (from the early '50s) I don't know of any other research on the subject. Again, my first encounter with the idea was sourced from Mitchell Cotter, and his discussion twenty five years later.

They tend to be rather stiff wires - likely rather effective given the forces. I'm also not convinced that marketing diagram depicts it correctly, however it's been several years since I've had the occasion to dismantle a V15-V so I can't remember exactly how the tie wire was fashioned on those.

I can only think of one cartridge that I've played with that was from the 70's-on that didn't utilize a tie wire. I think they're fairly ubiquitous.

 

[JP]

@anmpr1 this is a V15-V assembly:

 

[mackat]

Ortofon MC 20 Super SE, Thakker exclusive edition. Looks pretty flat for an MC.

 

[Newman]

....A MC cantilever was usually tied from the the back by a small length of 'piano wire', allowing the stylus to move in an up and down and circular motion, following the groove patterns, but not a front to back motion...

cutterhead assembly (not sure which model) showing a 'piano wire' tie down similar to the description found in Denon MC cartridge documentation

I notice that Rega have eliminated this tie wire from their MC designs. Can anyone illustrate for me how this works please? They describe it as "an ultra-low mass generator which is undamped (no tie wire) using a unique rhomboid pivot for the cantilever".

 

[mackat]

This is the first time I'm measuring an MM through the Elac PPA-2, and unfortunately I don't know its input capacitance. I asked ELAC a while ago, but they never responded. That being said, this VM95ML graph looks really weird to me. I expected a few dB of roll-off in the high frequencies, but not nearly -10 dB at 20k. Nor did I expect the +2.5 dB hump at 10k. Does anyone have an idea as to what could cause this frequency response? Perhaps there's a ridiculous amount of capacitance or its 47k isn't actually 47k? I'm stumped!

 

[levimax]

This is the first time I'm measuring an MM through the Elac PPA-2, and unfortunately I don't know its input capacitance. I asked ELAC a while ago, but they never responded. That being said, this VM95ML graph looks really weird to me. I expected a few dB of roll-off in the high frequencies, but not nearly -10 dB at 20k. Nor did I expect the +2.5 dB hump at 10k. Does anyone have an idea as to what could cause this frequency response? Perhaps there's a ridiculous amount of capacitance or its 47k isn't actually 47k? I'm stumped!

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Something doesn't look right. Not only the FR but the distortion which looks way to low at high frequencies and trending down at higher frequencies which is not right I don't think. Maybe someone know what would cause this. Can you give details on the chain used to capture this?

 

[mackat]

Something doesn't look right. Not only the FR but the distortion which looks way to low at high frequencies and trending down at higher frequencies which is not right I don't think. Maybe someone know what would cause this. Can you give details on the chain used to capture this?

Sure! For the VM95ML measurements, I used a Technics SL-1200MK2 with KAB fluid damper into an Elac PPA-2 phono preamp. From there, the signal continued into a Focusrite Scarlett 2i2 3rd gen, into Audacity on my M1 MacBook Air.

I recabled the turntable, as is a 2010 model that shipped with 300 pF+ RCA cables. The ones I installed measure about 140 pF; still a bit too much but certainly better than the originals. The VM95ML is not nearly as sensitive to capacitance most of the other AT cartridges, though.

Here are some new measurements that I did with the iFi Zen Phono (specified at 110 pF input capacitance, but read that someone measured 170 pF) in place of the Elac PPA-2. Better, but not by too much:

 

[mackat]

For comparison, here are measurements of the VM540ML that I just took using the iFi Zen. Previously, the system sample rate was 192 kHz while Audacity was recording at 96. I have since changed the system sample rate to 96 as well. This only appears to affect how low the scale goes.

 

[JP]

Sure! For the VM95ML measurements, I used a Technics SL-1200MK2 with KAB fluid damper into an Elac PPA-2 phono preamp. From there, the signal continued into a Focusrite Scarlett 2i2 3rd gen, into Audacity on my M1 MacBook Air.

I recabled the turntable, as is a 2010 model that shipped with 300 pF+ RCA cables. The ones I installed measure about 140 pF; still a bit too much but certainly better than the originals. The VM95ML is not nearly as sensitive to capacitance most of the other AT cartridges, though.

Here are some new measurements that I did with the iFi Zen Phono (specified at 110 pF input capacitance, but read that someone measured 170 pF) in place of the Elac PPA-2. Better, but not by too much:

View attachment 217242
View attachment 217243

 

[Tom C]

Ortofon MC 20 Super SE, Thakker exclusive edition. Looks pretty flat for an MC.

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That’s stellar! The Elac ppa2 is in my sights for my next phono stage. Sorry if I missed it, but what did you use for ADC when measuring?

edit : sorry. someone just asked and you answered a couple posts above.

 

[mackat]

That’s stellar! The Elac ppa2 is in my sights for my next phono stage. Sorry if I missed it, but what did you use for ADC when measuring?

edit : sorry. someone just asked and you answered a couple posts above.

No problem! The PPA-2 is quite a nice unit, I bought mine used a few months back. Mine has a bit of a hum that I haven't been able to get rid of in MC mode, though. Hopefully I can figure it out.

 

[JP]

I notice that Rega have eliminated this tie wire from their MC designs. Can anyone illustrate for me how this works please? They describe it as "an ultra-low mass generator which is undamped (no tie wire) using a unique rhomboid pivot for the cantilever".

This how ADC did it in their latest designs, though MI.

 

[mackat]

Ortofon MC20 MKII, an ultra low output model at only 0.07 mv! This one came mounted to a turntable I recently purchased, and it sounds quite good.

 

[Audiofire]

Can the difference in sound all just be differences in cartridge body resonances and LCR loading parameters?

I like MC cartridges. They were developed in order to solve some specific problems that are described in the Ortofon patent attached below:
"In 1946 the old name of the company was changed to FonoFilm Industry A/S and in 1947 Ortofon A/S was founded as a trading company under FonoFilm Industry A/S umbrella. This was done as a consequence of a considerable increase in demand from the whole world. At the same time ORTOFON was registered as a trade mark for all the products of the company and a guarantee for imported articles was made."

Our story

Ortofon

www.ortofon.com

These are the sources in the patent that can considerably impair distortionless vinyl playback:
(a) Frequency distortion results from resonance of the stylus and associated movable parts.
(b) Non-linear distortion caused by lack of proportionality between the mechanical movement and electrical signals.
(c) Vertical movement of the stylus owing to varying groove width.
(d) Mechanical oscillations imparted to the turntable system and supporting structure from external sources.

This is a further paraphrase of the inventor H. C. Arentzen:
The aim of the MC cartridge was to have an extremely small moving mass and high elasticity that minimizes the impact of stylus inertia, unreliable pressure on groove walls and wear on the imparted amplitude and frequency response. This achieves a low moment of inertia with regard to the axis of rotation. The torque in relation to moment of inertia and transverse forces on the stylus is designed to have a neutral position and a resonance frequency that is below the music content on vinyl records.