Cartridge loading

Around 1980, the B&W and Audire Florida rep was my neighbor near my family's St Augustine beach house.  He turned me on to both brands, and suggested a Supex 900 E+ M/C to replace my Ortophon.  I bought an Audire Diffet 1A  preamp, which had a three position impedance selector.  He changed the 40 ohm input resistor to a 10, really opening up that cartridge.  BTW, I had thought my Phase Linear Stacked Advent system was good, which is was for my grad student party system, but he enlightened me. 

The topic about Cartdige Loading is hot.
But here is something about Speakers Loading from Zu Audio:

https://www.zuaudio.com/low-voltage/2020/1/24/loading-resistors?mc_cid=709c630e33&mc_eid=cdb0d19c49

@antinn

That article was modeling the mechanical resonances as an equivalent electrical circuit. I was trying to show that the mechanical resonances were more complex than I originally thought, and if the cartridge goes into physical resonance (which is more likely at high frequency), then there will be a high harmonic distortion (EMI/RFI) produced.

Indeed it's more complicated than just a mass on a spring as there comes into play the vinyl resonance (I admit I never thought about that).
But getting a mechanical resonance radiate into RF range I think is not easy. Ultrasonic yes, but RF we are talking about some 40-50kHz at least.

Its my understanding that LOMC, are poor voltage generators, but good current generators which is why the new generation of LOMC preamps are current sensing.

Again: MC and MM cartridges work by the electromagnetic induction. What they generate is voltage. What I mean is if you play a cartridge unconnected what you will measure on its pins is a voltage but no current flow as the circuit is open. So cart is a voltage generator. Now, you in the electric circuit theory you can exchange current and voltage sources on the paper. You can redraw any circuit using voltage sources to current sources and vice versa. BTW the current source at teh Shures schemtics is wrongly drawn. Series resistance makes no sense with current sources. What I suspect the "current generator" thing mean is that LOMC's have a low internal resistance so for a given output voltage they will push more current. And this is of course a fact.

If a capacitor saturates because of the high harmonic current, and there is no dampening resistor, the only thing that is left is the capacitor equivalent series resistance (ESR). If the circuit current suddenly increases, this will by the back emf, dampen the motion of the cartridge armature (stylus-cantilever-suspension), and may depending on where on the record this is occuring (i.e. radial velocity), cause miss tracking. So long as the current was not outrageous and the capacitor is not damaged, and most will self-heal, once the current drops, the capacitor returns to function. So the event can be very transie

Sorry, cannot understand what you mean here. Which capacitor? Can you point me to the relevant passage from your links?

bydlo,

First, the sequence of events is dependent on the cartridge and the pre-amp.  One of the premises of this entire thread has been the limits of 'some' pre-amps.

This article is an extension of the first Shure article I referenced, and it goes deeper into the cantilever stiffness, with the risk of mistracking at high velocity.   http://pspatialaudio.com/analogy.htm#cantilever.  This mechanically induced instability will lead to harmonic distortion.

From this article https://www.analogplanet.com/content/current-affair-intriguing-mr-labs-vera-20-mc-phono-preamplifier, the statement is made that LOMC  "Moving coil cartridges output very low voltages but relatively high current on the order of tens of micro-amperes".  Dynamic microphones that operate on the same principle, state current output. https://www.audio-technica.com/cms/site/b0d226992d31e25d/index.html/

Depending on the pre-amp, using this as an example, https://sound-au.com/project06.htm, if there is a line to line capacitor with no dampening resistor, and IF the capacitor saturates from the harmonic distortion, then the events should be setup for a high current to occur.  So, it may be that the mechanical instability begins the event, but the consequence is that a small mistracking event can cause harmonic distortion that because of the poor preamp design leads to an even larger mistracking event.

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.