Cartridge loading

 Now, if someone can find International Audio Review 5, 1980 pp.31-159, the answer to the existental challenge of prove-it may be answered.

Have a copy in hand....   which is why I took exception to the thought that loading a cartridge down must adversely effect the ability to trace high frequencies.    I think the following text from IAR 5 sums it up pretty well

Now, as the force against the groove wall lessens
momentarily, the stylus’ motion is no longer as damped
by the compliance (springiness) of the vinyl interacting
with the mechanical impedance of the stylus assembly.
The stylus assembly is, as John Curl has put it, more
on its own. And that’s when the additional damping
imposed on the stylus motion by the electromagneto-
motive effects of Lenz’ law and a low load resistor can
come into play. Stylus tip damping, from whatever
source, helps the stylus assembly to cope with groove
rattling problems (note that cantilever pivot damping
in the cartridge might not, especially at higher fre-
quencies).

maybe accurately tracing high frequencies is the wrong term and loading can help prevent the creation of "non-source contained" high frequency information.

dave

@intactaudio That is what the 47K input standard is supposed to be for- a slight amount of damping. I don't see in the text you quoted how the cartridge was set up- was it driving a very high impedance as a control or 47K?
@antinn  The interesting article you linked refers to self-resonance of inductors as a consequence of using them in equalization circuits. I don't see anything in that article about how the RFI generated by a cartridge can interact with the phono section. Pete Millet's website is quite an asset to those interested in audio!


What I have found is that there are two aspects of RFI issues in phono preamps. The first is pretty obvious; the resonance of the tank circuit caused by the cartridge inductance and the tone arm cable capacitance. This can cause overload of the input circuit if it has poor overload margins. The other is less obvious which is the inherent stability of the circuit. There is a device known as a 'stopping resistor' which is used to prevent oscillation at the input of a grid (in the case of tubes) or gate (in the case of FETs). But some designs don't use stopping resistors and can oscillate briefly if presented with the right circumstances. This is how a phono section can generate ticks and pops; this is a fairly common problem is why many people think than LPs are a lot noisier format than they really are. 

Dear @intactaudio  : Yes that could be because limit the tracking stylus tip is not so easy and if we are " thinking " to do  by the loading electrically  effects the posibility to overdamps the stylus tip motion in unimaginable due that the stylus tip motion inertia is really high.

The more " extreme " mechanical stylus tip damping exist through the Townshend TT where the oil/silicon damping is practically at the stylus tip and things are that just no overdamping, I had the experience to listen at least twice that TT/tonearm andthe kind of damping it has makes a very enjoyable listening experiences. More as the last sentences PM information you shared.

R.

atmasphere,

The article I referenced was only to address the affect of inductors.  When you say, RFI, are you talking radio frequency interference, or in general, electro-magnetic interference (EMI)?  EMI encompasses conducted emissions (CE) , conducted susceptibility (CS), radiative emissions (RE), and radiative susceptibility (RS). My background includes testing equipment to EMI requirements, so I am just trying make sure we are on the same page when communicating.  However, Peter at Soundsmith addresses the concept of stylus jitter https://www.sound-smith.com/articles/fixed-coil-vs-moving-coil-why-make-jump-different-technology. 

I also have experience with vibration testing.  So when I read all this, my analogy is that stylus is tracking the record such that you want the transmissibility (essentially the ratio of the record grove to the stylus-cantilever movement) to be unity, that way the stylus-cantilever reads exactly the groove.  If the transmissibility drops below unity, then the stylus-cantilever-suspension is absorbing energy and there will be loss of data.  It may read the frequency correctly, but the signal output will be lower than normal, and this could be frequency dependent, so an oscilliscope trace may show some 'suck-out' at the affected frequencies.  The list of items that can cause transmissibility less than unity can be of mechanical origin (such as too much VTF) or electrical (such as circuit speed).

If the stylus-cantilever-suspension transmissibility is greater than unity, but not resonating then it will output more data than what is on the record, i.e. it may read the frequency, but the signal output may be high than normal, but again this may be frequency dependent.  So, an oscilliscope trace may show some peaking at the affected frequencies.  The list of items that can cause transmissibility greater than unity can be of mechanical origin (such as VTA) or electrical (such as cartridge loading and maybe an electrical circuit causing a weird impedance).

However, if the stylus-cantilever-suspension resonates, the transmissibility increases many times causing the stylus-cantilever assembly to move far greater than what is in the groove, thee output signal to increase proportionally, and depending on whether the stylus maintains groove contact, and depending on the pre-amp overload margin can lead to massive harmonic distortion (smearing of the output signal, i.e. conducted emissions) with distorted sound, and/or pops.  

Ergo, anything that effects the stylus-cantilever-suspension stiffness, be it of mechanical or electrical origins can affect its ability to properly read the groove.  And, since low, mid and high frequency information can simultaneously exist, there can be shall we say over 20,000 opportunities for this unravel.   Yes, its a mircale that this works, but as Corey Greenberg said many years ago, a 1000 years from now, good luck trying to find a CD player, but you could play a vinyl record with a pine needle.

@intactaudio

Now, as the force against the groove wall lessens
momentarily,...

Very much agree with that. EMF damping I’ve been talking about. Thanks for sharing Dave.
@atmasphere Don’t really buy the RFI argumentation, sorry. Putting aside simple and super cheap solutions like grid stoppers existing for decades, I cannot see how the RFI conspires to always give the effects exactly mimicking underloaded (high R) cartridge.