Cartridge Loading.....Part II

Dear @wynpalmer4 : I understand you but due that some gentlemans as lewm just did not reads the whole cartridge loading threads then are reduntdant on the issue one and again and other gentlemans what want is to " win " the discussion or " hit " to some one else and of course always exist the stupid and the stupidity.

. Sorry that disturb you and sorry for what I will posts next.

 

R.

@lewm : this is what Wyn posted before your post:

""

I was the one who wrote previously about Faraday’s Law and Lenz’s law in support of Carr’s assertion.

For your information, I have designed DIY phono stages that embody the characteristics that he espouses- very high supersonic overload characteristics for example- and are extremely compliant to the RIAA characteristic, very low noise, and essentially unmeasurably low distortion. There are several hundred of them out there...

In any case, there are no conservation of energy issues here. The mechanical energy of the groove wall reaction to the gravity induced downforce (i.e. the forced motion of the stylus) "uses" Faraday’s law to produce an output EMF (voltage). That voltage produces a current that complies with Lenz’s law- which essentially defines the inductance of the coil and occurs as an energy conservation consequence- and that current is defined by the total impedance of the coil- the inductance, the capacitance and resistance- the equivalent load impedance in fact.

The back emf is just due to the inductance, and is proportional to the frequency.

For a 10uH inductance at 20kHz, the impedance is about 1.6ohms, so relative to a 100 ohm R the back emf generated that opposes the input voltage is about 1.6/100 of the input voltage, and 90degrees out of phase, so it’s about 0.1dB of the signal amplitude.

Yes, the back emf opposes the motion of the cartridge, but it’s very small compared to the generated voltage- which is due to the conversion of mechanical energy to electrical energy as described above- and essentially can be ignored in calculating the dynamics of the cartridge arm system. """

 

 

and years before in the same issue he posted:

 

 

""" effects of heavy resistive loading you state could be definitively true- certainly not on tracking which is demonstrably false based on IM tests on tracking performance that I have incidentally performed as a function of load. While mechanical impact does occur as a result of electrical load- there is some back emf necessarily generated by the signal current that affects the mechanical motion, but a quick back of the envelope calculation using Lenz’s law and the 10uH cartridge suggests a 2 orders of magnitude difference between the generated signal and the back EMF for a 100 ohm load at 20kHz- certainly not enough to cause tracking issues """

 

and this post too years ago by Wyn:

 

"""" By the way, I constructed a model for the cartridge back EMF using Lenz's law and incorporated it into my simulations.
For those who are interested, the simplest version of the law is V(t)= -LdI/dt.
In this case the parameters can be measured (the LC100A meter from Ebay is a great way to do it) and the back EMF acts to oppose the voltage developed in the coil. The fractional change (attenuation) in the signal voltage is easy to calculate as it approx. equal to -L*2*pi*frequency of interest/Rload. So, it's inversely proportional to the load R and proportional to the frequency. """"

 

After all those years why you did not learn or at least try to understand about that issue? sorry.

 

R.

 

 

Incidentally, I don't intend to further participate in this exchange.

@wynpalmer4 

That's unfortunate.

I was/am familiar with Lenz's Law. I was simply hoping you could elucidate on how the input of the phono preamp (where the load is) provides a back EMF, or it I simply was misunderstanding what you wrote. I'm perfectly open to learning something new.

Dear Raul, I recently posted a URL from Wiki that contains a figure which I thought is instructional in understanding Lenz' Law.  Some describe Lenz' Law as the electromagnetic equivalent of Newton's Third Law of Motion. My opinion-less post with the URL preceded the one from Wyn that explains Lenz' Law in words rather than pictures. Other than that, I have been sitting on the side lines. I did not and do not take any position, because I am not qualified at the level of the best contributors, but I am here to learn. So I wonder why I am now the target of your invective. What makes you think I have not been reading the posts by Wyn, Ralph, and Dave, the only 3 people on this thread who are qualified to discuss the subject at hand? 

Cut back on the coffee, take a tranquilizer, get some therapy.  Do whatever the f*** you want but leave me alone, please.

@lewm  , I did not saY THAT. tHIS THREAD IS ONLY A FOLLOWER ( tITLE: CAN YOU READ THAT: PART II ? ) of not only another thread because the more critical about happened years ago and in the middle exist other threads here and in wbt forum and other forums. 

It's not invective but you normally just do not read all the information not only in this thread subject but in other thread audio subjects and this is not invective but a fact. Sorry to disturb you.

 

R.

 

I repeat, stay away.

Well you was who posted and I only posted an answer. If you don't want this happens then stop to post refering to me. Easy.

 

R.

 

 

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?

@lewm 

Congrats on the new phono stage, but I would think the Steelhead might still be a step up from the BMC MCCI, but maybe I'm wrong. . .what's your impression between the two? 

I have two complete systems in two different listening areas in my house. The Steelhead runs a system in my basement based on Beveridge 2SW speakers driven by Beveridge direct-drive amplifiers. The Beveridge outboard woofer system is long gone; I use a pair of Transmission Line cabinets employing KEF B139 woofers for frequencies below 80Hz. That system is single-ended all the way, as is the Steelhead. My upstairs system consists of Sound Lab 845PX speakers with modified crossovers driven by Atma-sphere amplifiers. The preamp is either an Atma MP1 or the 3160 Phonolinepreamp that was conceived and designed by Raul and his engineer friend. The entire system is all balanced from cartridge to speakers. The BMC was made for balanced operation, so I felt constrained to test it in the balanced system. To do that, I had to remove my CDP from its shelf and replace it with the BMC. The BMC goes into a balanced line level input on the 3160, right now. I can already tell the BMC is good, but what would make you think necessarily that the Steelhead would be better? Right now, I cannot make a direct comparison, at any rate.

@lewm 

how does the BMC compare to the 3160 phono stage ?

Don’t have a formed opinion yet.

Plus, db are units expressing the ratios of voltages, having nothing to do with current. Anyone?

DeciBels refer to voltage, yes.

The higher gain settings must invoke downstream gain stages that add to signal voltage output by the indicated db’s. Is that correct?

Yes. Transimpedance phono sections have cartridge-dependent gain as you point out. There's a limit to this, for example you really don't want to push most opamps past about 20dB of gain and since the cartridge is an uncontrolled variable in this, you will need to change the gain somehow downstream.

 

Using the ZYX Universe, which has an output of 0.24mV and an internal R of 4 ohms, the gain is as much as you’d want, at the 0db setting. So, if you estimate the current output of the ZYX as 0.24mV/4 ohms or ~60uA (micro-amps), it would seem that any LOMC that makes significantly more current might be pushing too hard. But I also notice there is a certain unpredictability or non-linearity (in the sense of overall SPLs per estimated current) to what really happens. Anyway, there is no problem mating the MCCI with any typical LOMC. (If the current is much less than 60uA or if the voltage output of the unit is not resulting in satisfying drive, then of course one can add +7, +11, or +14db by activating gain circuits under the hood.) I found that the ART7, with 0.12mV output and an internal R of 12 ohms (which calculates to much less current at standard stylus velocity), also can drive the MCCI at the 0db setting very handily, but I think it sounds a bit better at the +7db of gain setting. This is all well and good. The question in my mind remains, is the result really "special" or just very good at the level of any other very good voltage gain phono stage. Or as Cole Porter wrote, "Is it the good turtle soup or merely the mock."