Cartridge Loading.....Part II

Dear friends: Only to show you what posted ( his words not mine. ) over the years in the same subject that gentleman that posted:

""  has been trying to put words in my mouth.  ""

 

Read and make your own judgements about:

 

 

" the lower the resistive load it drives, the harder it becomes to move the stylus since that is where the mechanical energy is input to be converted to electrical energy. IOW the cantilever becomes stiffer. If you have a means of testing the mechanical resonance of your arm/cartridge combination, you can see that this affects the mechanical resonance since in essence you are reducing the compliance of the cartridge. "

 

STIFFER, RESONANCE arm/cartridge AND COMPLIANCE are the critical words he used.

Well you can go to any resonance frequency arm/cartridge combinations and make ( with the same arm effective mass. ) calculations changing the compliance and you will see that you have to change several CU to achieve a different arm/cartridge resonance frequency. So that " stiffer " at least does not affects: resonance frequency arm/cartridge in the alevel needed to.

 

 

"" The loading has no effect on the cartridge other than making the cantilever harder to move. ""

WELL FIRST SAID AND TALKS ABOUT CARTRIDGE COMPLIANCE AND IN THIS STATEMENT HE SAID THAT LOADING HAS NO EFFECT OTHER THAN..""

When he posted that statement I@intactaudio posted:

 

*********Isn't that essentially suggesting that compliance has no effect on the sound of a cartridge? ******

 

Another post by him where I'm supposing to put words in his mouth:

 

""""  It certainly has an effect on the cantilever, and if you look at my prior posts you'll see that I suggest this may affect its ability to trace higher frequencies. """"

 

NOW WHEN THE RESONANCE FREQUENCY OF ANY ARM/CARTRIDGE CHANGES AND EVEN IF THAT RESONANCE FREQUENCY IS OUT OF THE FREQUENCY IDEAL RANGE MAINLY COULD AFFECTS THE BASS RANGE.

 

Here again a " reloaded " post with the same mistakes:

 

 

"""""Even though its a tiny amount of power, it will make the cantilever stiffer and less able to trace high frequencies. It can and does affect the interaction between the arm and cartridge (effective mass and mechanical resonance). """

 

ANOTHER ONE RE-LOADED POST:

 

 

"""""" reducing the ability to trace high frequencies and certainly affecting the mechanical resonance of the cartridge and arm combination. """"""

 

AN ANOTHER ONE.

 

 

""""""" I have maintained is that the additional stiffness may decrease the ability of the cartridge to trace high frequencies """""""

 

AND LOOK THE NEXT ONE.

 

 

"""""""" Empirically speaking its easy to deduce that the load is affecting the ability of the stylus to trace the groove, which is why we see distortion as essentially the stylus is mistracking. """"""""

 

 

THIS IS REALLY SEALLY AS  @mijostyn  POSTED IN THIS THREAD.

 

 

""""""""" This makes the cartridge cantilever stiffer and less able to track higher frequencies. This is why the resistor can act as a tone control. """""""""
 

YES THERE ARE SO MANY POSTS.

 

 """""""""" (like less than 100 ohms) its possible to reduce the cartridge output and also decrease high frequency tracking abilities. """"""""""

 

 

"""""""""""" the loading will decrease the compliance of the cartridge, which in turn will reduce its high frequency response """"""""""""

 

THAT MEANS THAT LOADING CHANGE THE FREQUENCY RESPONSE. GO FIGURE  ! !

 

J.Carr posted that that frequency response change is " BOGUS  ".

 

R.

I suspect that the mention of Lenz's Law with respect to back EMF may be a bit misplaced here.  The simple story of back EMF when it comes to a speaker is the inertia forces the cone to continue to move after the signal tells it to 'stop and go the other way'.  This 'undriven motion' will generate an additional voltage which will then appear at the amplifier.  Lenz comes into play here when the low output impedance of the amplifier appears as a near short allowing a 'large' current to be generated which following lenz will create an opposing current which acts as a 'brake' of sorts.

The Key difference between back EMF in a driver and a cartridge is the speaker is electrically driven to create a mechanical sound and the cartridge is mechanically driven to create an electrical signal.  In a driver inertia causes an additional mechanical movement that is electrically 'damped' by Lenz.  Unlike the speaker where the heavy lifting is done by the electrical signal, the cartridge has the groove as the guiding force.   A lateral cut groove drives the diamond left and right and an important  difference is after a peak in the left direction the groove wall forces the tip back in the other direction and the inertia causes instantaneous pressure on one wall to increase as the pressure of the opposite wall decreases.  There is inertia but no real 'overshoot' to invoke Lenz like in the case of a speaker.   

When you look at a stereo cut where there is a vertical component in addition to the lateral things change.  On the downhill path to a valley a similar thing happens to the lateral situation.  The tip hits the low point and reverses direction up momentarily increasing the downforce.  It is when it reaches the following peak where I see inertia coming into play since there is nothing beyond gravity to push things back down to the next valley.  After the peak,  inertia will keep the tip going in the same direction resulting in the situation where downforce approaches (or reaches) 0.   If you look above at the screen grab I posted from CBS STR112 it states that the dynamic groove wall force can vary from 2x the static force to nearly 0.  The simple solution to mistracking is to add VTF until you are kept a 'safe distance' from 0.  I think it is generally accepted that too much tracking force leads to record and diamond wear and too little force leads to mistracking so it is the 'approaching 0' aspect that needs to be looked at.  It is my belief that Loading can effect the behavior on the vertical uphill peaks causing a dynamic brake if you will which results in better dynamic tracking ability. 

An interesting test of this on my list of things to try is to compare the results of loading with stereo vs. mono records.  For what I say above to hold water, I would expect the results of loading a stereo record to be greater than that of a mono record due to the addition of the vertical component. I should get time to try this experiment around 2024 :-)

dave

 

Thank you Dave for the excellent explanation... I really appreciate your succinct and elegant description!!

Lou

+1 Dave. Thanks! Your description also supports my prior assertions- so lookout- Raul will be after you next 😁

 

To satisfy my curiosity and because life is short, I purchased a BMC MCCI Signature ULN. This unit has gain settings of 0, +7, +11, and +14db. My question to anyone is what is the meaning of these db values? At the 0db setting, the unit produces quite a bit of phono voltage gain at its output; I would guesstimate about 60db. Plus, db are units expressing the ratios of voltages, having nothing to do with current. Anyone?

Here’s what I think it might mean. The unit may have a certain baseline voltage gain at its output, but that is dependent upon its interaction with the current fed into it by the cartridge, which will vary depending upon the BMC’s own input impedance (I assume it's greater than zero) and the cartridge’s output voltage and internal impedance. Because of this interdependency with the cartridge, the voltage gain at the output cannot be specified by the manufacturer. (It will be different for every cartridge, and I have already verified that.) So the "0db" must be referenced to whatever is the signal voltage output based on its input current. The higher gain settings must invoke downstream gain stages that add to signal voltage output by the indicated db’s. Is that correct?