Cartridge loading

bydlo,

After further thought, here is my best hypothesis, and it really is just a 'perfect storm', for all the variables to come together.

1.  Many LOMC cartridges have very wide bandwidth, out to 47kHz and maybe even beyond.  So, the harmonic distortion that starts the event may begin at a very high inaudible frequency.  

2.  For capacitors used in audio such as Elna, Nichion, etc, a 25V, 4.7uF capacitor may only be rated 25mA, but this rating is at 120Hz.  There is a Coefficient of Frequency for Rated Ripple Current that for higher frequencies, you can add 20% or more to the rating.   But, the capacitance can drop with higher frequency, so this all adds uncertainty.  And. as I addressed in my very first post, per this very old article www.aes.org/tmpFiles/elib/20200131/2623.pdf; the preamp design has a lot of influence on the entire circuit.

3.  If the event first starts at very high inaudible frequencies, and the preamp circuit saturates, overloads, oscillates or otherwise becomes unstable, and if a current surge occurs, then the LOMC cartridge may now try to function as a moving coil instrument https://www.yourelectricalguide.com/2017/01/permanent-magnet-moving-coil.html; "When the moving coil instrument is connected in the circuit, the operating current flows through the coil which is mounted on the spindle. Since the coil is placed in the strong field of permanent magnets, a force is exerted on the current carrying conductors of the coil which produces deflecting torque.".  

4.  If item 3 above occurs, the cantilever will stiffen.  The stiffening of the cantilever assembly will cause the cartridge effective compliance to decrease.  If the LOMC cartridge is a medium compliance with low VTF, then it stands to reason that the cartridge will likely miss-track at audible frequencies.  If the LOMC cartridge is a very low compliance (i.e. Denon DT103R) with high VTF, it may not miss-track.  However, when the cartridge cantilever assembly stiffens and the effective compliance decreases, the cartridge-arm resonant frequency will increase, and this 'may' depending on the cartridge-arm combination increase the cartridge-arm mechanical resonant frequency into the audible range.

Dear @antinn  : There is " something " in your 4. point where you said:


"""  The stiffening of the cantilever assembly will cause the cartridge effective compliance to decrease. If the LOMC cartridge is a medium compliance with low VTF, then it stands to reason that the cartridge will likely miss-track at audible frequencies. """

Medium compliance, this is what P.ledermann states about: 

"" medium to low compliance cartridges. Cartridges with a compliance between 22 and 10. Most cartridges are between 22 and 10 in compliance.  ""

I asked atmasphere that proposed the same ( almost. ) hyphotesis you posted in  point3. and 4. that he showed wich kind of electrical current must need it not to stiff the cantilever but to make the stylus tip mistrack groove modulations.
A medium compliance LOMC device say 16cu normally be a very good tracker even in very high velocities recorded in the LP grooves an even if are recorded at the most inner recording LP surface.

Now, I posted that for that medium compliance cartridge could has a mistracking problem that compliance has to goes really low, lower than 10cu and this is almost impossible that could happens with the stiffness of the cantilever.
Not science only common sense. I would like that you or other gentleman come here to shows those " numbers " that can cause the effect detailed in your 4. point. At the end it's the discussion main issue.

Ikeda designed non-cantilevered cartridges with extremely low compliance and obviouly with 1gr higher VTF that a medium compliance that normally comes with 1.5gr and up and I never read any report of such kind of problem you posted and that was what I asked to atmasphere.

Your hyphotesis probably can't be proved it can happens .

In the other side, no single audiophile in no single audio forum sites over the world never reported that phenomenon.

Seems to me that's more easy that the mistracking happens with a bad mistmatch between cartridge and the tonearm about resonance frequency in between that by the loading resistor combination with the cartridge/phonostage. Only an amateur opinion.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

rauliruegas,

As I said it was a hypothesis, and as a hypothesis, there is no empircal data to support, but for me only deductive reasoning from a multitude of sources that I have addressed in a number of posts. But, your statement that the compliance cannot stiffen beyound some point because of the stiffness of the cantilever without any data does not make sense either.  The compliance is more than than the cantilever stiffness; it includes the suspension, and this is addressed in many of the articles here http://pspatialaudio.com/index_help.htm.   If current in the circuit from the harmonic distortion exists, it can by the back-emf torque the coil to 'effectively' stiffen the the cantilever assembly causing the cartridge compliance to decrease, the stiffer the cantilever, the worse it should be.  As far as an Ikeda non-cantilever cartridge which I have no knowledge of and found no data on the web, but assume is similar to a London-Decca design, the unique design with very low compliance may be immune to this event.  As I implied with the Denon example, for a very low compliance cartridge, the design is so stiff to begin with that there is not much margin/room left to futher stiffen. But, there are medium compliance cartridges with very stiff boron cantilevers. If a medium compliance 22 cartridge with only 1.4-gm VTF was to decrease to 10, but, if at 10 requires 1.8-gm VTF, that is a difference of almost 30%, and in my mind it stands to reason it could mistrack.  It becomes very dependent on the individual cartridge design. I never said, it was for it was for every cartridge. But, the cartridge and tonearm form a mechanical resonance, which is very different from the loading resistor that forms an electrical resonance, but that does not mean that one cannot manifest itself as the other, especially for LOMC.   There is an old saying, We do not what we do not know.   Otherwise, we agree to disagree.  In the meantime, I use only Soundmith moving iron cartridges (Paua & Carmen on two different arms). And, to be honest, after all my reading on LOMC, I highly doubt I will ever dip my toe into those churning waters. 😁

Dear @antinn  : I know that the cantilever could be stiff through that current and all your hyphotesis make sense to me.
The issue is that which kind of  current level is need it to happens that mis-tracking?

Of course that could happens but the reality is that exist no audiophile evidence nowhere of any one that can attest an experience like that.

Now and on the mechanical side the compliance of any cartridge can change over time over the playing hours and normally we don't change the VTF due that the manufacturer VTF range iin LOMC cartridges is to  the coils be centered.

Thank's for your answer. As a fact the issue is really exiting to think/discuss on it.

R.

Dear rauliruegas,

The amount of current is just one of the many questions left to answer.  And, I agree with your other statements.  A basic challenge with vinyl is the difficulty in measuring it, and this is very consistent with electro-mechanical systems.  In oil lubricated turbo machinery there is a bearing known as the Kinsbury Tilt thrust bearing that is widely used, and has been for over 50 yrs.  But, Professors have been  studying it for over 50 yrs trying to unlock all of its secrets.  However, my last turbo machinery project was having nothing to do with that; we used magnetic bearings that could generate almost 1 MB of data every minute; we had no trouble measuring everything.

But to me, and I suspect you by your last sentence,  one of endearing qualities of vinyl is the challenge, which pushes it into a different category other than just listening.  It is not plug and play.   Vinyl takes some skill (and tools) and perseverance (devil often in the details) to get it to sound good and that can be very rewarding/satisfying.  However the 'vinyl-challenge' obviously can frustrate some (if not many 😁).  And, there are the unknowns which stimulates the never ending conversation (frustrating some, engaging others, all good as long as we stay civil), and a lot is still an art-form (of course that defies the IOT - Internet of Things🤔).  This site is doing some measurements of cartridges though-
  https://www.lowbeats.de/tonabnehmer-messungen-bei-lowbeats-tests/.  Its in German, but Android devices will translate.  It is surprising that Stereophile has not taken a lead in this area, but JA who for sure leans to digital, is probably less than enthusiastic.  

I am not a luddite as you can see from the 1st paragraph above, but, the true irony may be that this 2015 report "ARSC Guide to Audio Preservation", commissioned by the Library of Congress states:  "Vinyl discs are the most stable physical sound recording format developed to date; they can last 100 years in a controlled environment.", and the Voyager probe carries a gold record that will last for centuries and beyound with simple details on how to play back.  

Best Regards, 
N.