Cartridge Loading- Low output M/C

Thanks for all your help Al.

As the Ortofon is a fairly low output MC cartridge there are generally two components to the frequency response which interact.
1. The electrical LCR response.
Contrary to what has been said, for LOMC the capacitance, unless it is quite large (in the order of .1uF), is essentially irrelevant and the objective is to set the response to look like a single pole LR system.
See the MC cartridge section in this article.
http://www.hagtech.com/loading.html
In most cases a resistance close to 100 ohms is fine- largely because the coil DC resistance is often a proxy for the inductance (most cartridges have a similar internal magnetic structure) and turns out to be close to 5 ohms and c.0.5mH, (There are exceptions- Miyajima cartridges are a good example of this) and as a result a 100 ohm load gives you a well damped electrical system (no peaking) with a bandwidth of c.35kHz. This results in c. 0.3dB attenuation at 10kHz and c. 1.1dB at 20kHz. You could try to flatten the response out a bit by greatly increasing the cap, but it’s tricky and usually impossible because of the tip/cantilever/suspension resonance. 
To illustrate this point, use the Hagtech calculator and set the capacitance to 200pF and the inductance to 0.5mH- the resonance is at 500kHz and into a 47k load the Q is c.30!  To reduce the resonance to 50kHz the cap must be increased to 20nF and the Q (R/inductive impedance) becomes 300! If the load R is reduced to 100 then the Q is 0.06 for the 200pF cap and 0.6 for the 20nF cap.
So, clearly a low load R reduces the electrical system to a simple, single pole RL form.
2. Tip/cantilever/suspension resonance.
Typically this looks like an electrical equivalent LCR resonance plus an additional HF pole. I wont go into the math, but it’s not unusual for this to have a resonant peak in the high sonic/supersonic range- 18-40kHz, and with an amplitude of 2-6dB at the peak. This is NOT the electrical resonance and cannot be corrected for by changing the loading of the cartridge. It can be modelled as an LCR plus an RC followed by a unity gain buffer or as a mismatched transmission line.
Essentially the cantilever flexes and resonates when stimulated by the movement of the stylus tip and the response is damped by the suspension/coil dampers.
So, the bottom line is- you’ll never get it perfect. You can either listen and decide what you like, or use a test record to check the sonic response. A couple of other things, the RIAA deemphasis of your amp comes into play, and it’s not unusual for that to be off c. 0.5dB or so over some frequency range, and most amps have restricted frequency responses to reduce the infrasonic and ultrasonic signals.
Also, your room/speaker response is probably poor with errors at least as large as any from the above sources, so unless you’ve characterized and corrected that then listening is probably your best bet.

Wynpalmer4 5-25-2018
Contrary to what has been said, for LOMC the capacitance, unless it is quite large (in the order of .1uF), is essentially irrelevant ....

As explained earlier by me, and by Atmasphere (Ralph Karsten of Atma-Sphere Music Systems), and in the statement I quoted by Jonathan Carr (Lyra cartridge designer), while load capacitance is indeed essentially irrelevant to the cartridge, it is not irrelevant to phono stages whose design is such that RF frequencies received at their inputs can have audible consequences.

Regards,
-- Al

I may not be a renowned Audio Designer, but I am a somewhat renowned IC designer with credits that include cell phone transceivers and high performance opamps. 
In truth, the issue with phono stage RF has little to do with the capacitance loading- rather it's that many RIAA stages are designed to be non-inverting and lack the additional pole necessary to provide attenuation at ultrasonic frequencies and above. For example:
http://audiokarma.org/forums/index.php?threads/ad797-phono-stage-build-and-help-desk-thread.501186/p...
Where I discuss this very problem as an aside to optimizing an opamp based phono stage.
The non-inverting amplifiers used in an RIAA stage never have a gain below unity unless an additional pole is added. It's hard to see why adding a capacitance of significant value to the input of a phono stage helps when the self resonant frequency of most larger value caps is well below the RF region of interest. Indeed, if that is your concern, then adding several caps of scaled value 1-2 orders of magnitude apart, say 0.1uF//3300pF//100pF as the cartridge load would be the way to go, and who does that- except as an extra pole in a non-inverting RIAA stage.
I'm a believer in fixing the problem where it exists and not by adding an additional parameter to an already over-constrained problem.

I have my Nova II phono pre capacitance set at 100pF for my Delos and I use an AQ Cougar phono cable with total cap at 60pF. Lyra suggests using the lowest cap cable you can, and for me it does make a difference, as I was using a very high cap cable in the 350pF range with loading at 121 ohms.
The dynamics and resolution is so much better now.

Just for interest sake, I ran some simulations with an "ideal" MC cartridge with a 5mH/5 ohms coil in conjunction with a near ideal active RIAA design with non inverting amps and the extra pole.

The ideal load- the one that results in the closest compliance to RIAA
is with 22nF||110 ohms (+/-.06dB 20Hz-20kHz). It also has 50dB of attenuation (relative to the ideal RIAA stage) at 1MHZ and 95dB at 10MHz. Dropping the load R to 100 ohms reduces the 20kHz output by 0.2dB. 
Increasing the capacitance to 0.1uf and reducing the load to 68ohms is almost as good as this.
None of these simulations include the mechanical response.
Anyway- as can be seen there is no perfect answer. There are many combinations of load R/C that are pretty well equivalent and you can't even simulate or calculate it to find a decent answer as no MC cartridge maker that I am aware of provides even simple models for their device, even when asked.

Unfortunately accentuated dynamics and resolution all too often mean a really nasty peak at the HF. In my experience, getting a good test record and testing the RIAA response can be a real eye opener.
Most of the differences in response that occur due to changes in load are in the 10k-20kHz range.

Dear @wynpalmer4: " I may not be a renowned Audio Designer..."""

Problem with we audiophiles is that almost all always think that reviewers and manufacturers are the ones that not only kno everything but that what they say always is " the Bible " and almost all of us are docile followers, pity for say the least.

The other problem is that we audiophiles think we understand " everything " in audio with out take in count that all of us are ignorant people in several audio subjects when in other audio subjects our ignorance levels are lower.
Additional to that when I speak of ignorance levels peoples feel that I’m trying to offend/hit them when it’s in not way. Ignorance is just that: ignorance.

Good that you came here to put a true " ligth " in that regards because the atmasphere seller is spreading that same capacitance issue all over the internet forums and like here @krelldog is " facinated " with 47koms @catcher10 just does not understand what you posted.

We all audiophiles in reality are not educated in what is wrong or good in what we are listening at our place/home and this ignorance level is the real brake that stops the high end faster developments. Go figure, we are in 2018 still using tubes in phono stages and the real problem is that audiophiles are jumping of hapiness with. To each his owns.

""" In most cases a resistance close to 100 ohms is fine- largely because the coil DC resistance is often a proxy for the inductance .... and as a result a 100 ohm load gives you a well damped electrical system..."""




Several years ago I remember a top LOMC cartridges evaluation made it in TAS where one of the reviewers was the TAS’s editor ( that pass away. ) where as was his " trend " always loaded his LOMC at 47kohm but he did it for way different reasons where one of them was that he was losting to fast his auditive sensitivity due that for many years he listened his audio system at way to high SPL ( he had the Infinity IRS loaned from years. ) and where that sensitivity affects more is at the high frequency range that’s what shows that wrong 47kohms loading. We " love " that " transparency/spark "/detail in that range with out take in count that only are higher distortion levels. You said it:

""" Unfortunately accentuated dynamics and resolution all too often mean a really nasty peak at the HF ....... ferences in response that occur due to changes in load are in the 10k-20kHz range. """

Well, audiophiles as me sometimes we don’t like 100ohms loads because in many audio systems makes that we " feel " that the sound is " dull " but the problem is not on the load it self but in the system/room interaction and that our MUSIC/sound priorities are wrong choosed and sometimes is because we not only don’t attend often to live events but there are people that not even does one time in a year ! ! and this is a serious trouble.



"""
I’m a believer in fixing the problem where it exists and not by adding an additional parameter to an already over-constrained problem. """


with different words I posted something like that.

"" you can’t even simulate or calculate it to find a decent answer as no MC cartridge maker that I am aware of provides even simple models for their device, even when asked. """

it’s out of our control.

I’m way ignorant in several audio subjects and I wish to have a tinny very tinny fraction of your level knowledge/skills and experiences.

For my part really appreciated your posts. A learning lessons for all we true audiophiles that are always willing to learn and trying to sell nothing.


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Wynpalmer4 5-25-2018

The non-inverting amplifiers used in an RIAA stage never have a gain below unity unless an additional pole is added. It’s hard to see why adding a capacitance of significant value to the input of a phono stage helps when the self resonant frequency of most larger value caps is well below the RF region of interest. Indeed, if that is your concern, then adding several caps of scaled value 1-2 orders of magnitude apart, say 0.1uF//3300pF//100pF as the cartridge load would be the way to go, and who does that- except as an extra pole in a non-inverting RIAA stage.
I’m a believer in fixing the problem where it exists and not by adding an additional parameter to an already over-constrained problem.

Thank you for your responses. I must say, though, that despite being a highly experienced electrical engineer myself (in my case analog and digital circuit design for defense electronics), I don’t see the relevance of this statement.

What I, Atmasphere, and Jonathan Carr have said in regard to load capacitance, and which the Hagtech calculators you referred to will confirm, is that in the case of LOMC cartridges **minimizing** load capacitance will increase the frequency and reduce the amplitude of the resonant peak which occurs at RF frequencies as a consequence of the interaction of cartridge inductance and load capacitance. Both of which are desirable goals, although it presumably won’t matter much if at all in the case of **some** phono stages (such as my Herron and I would assume the phono stages that are built into Atmasphere’s preamps).

But in the case of phono stages whose design is such that RF energy received at their inputs may have audible consequences keeping that resonant peak as small as possible and at as high a frequency as possible will mean that less resistive loading will be necessary to tame that peak. Which in turn can often be beneficial sonically, as has often been attested to by many highly experienced and astute audiophiles. A notable example being Larryi, who posted earlier in this thread.

So I’m not understanding why your statement that I quoted refers to adding capacitance, rather than minimizing it, or what the relevance of that statement’s concluding sentence may be.

Regards,
-- Al

^ I agree.......I have followed pretty much everything JCarr has stated in other forums about loading and all I can attest is my listening experience is much better for it.
The part that I focus on is that your LOMC should not be tasked to work so hard that it stiffens compliance, I can't see any good from that.

Unless you like buying a new cart sooner, much sooner, than normal.

@catcher10:  " stiffens compliance "?, you or any one but the cartridge designer can change cartridge compliance, certainly load can't do it.

R.

Dear @almarg : My " worry " here is not whom is rigth but more if things are pratically to any one of us, if we can do a easy as to load impedance changes. Normally cable manufacturers does not gives cable capacitance. I put the KK example but if you go to Audience ( OP cables. ) you can find out nothing.

Many times you can't know the ps fixed capacitance and the ones that comes with capacitive loading switch this works only when using MM but not when LOMC.

Ok, what's the problem to tame the peak ( as you said. ) loading at 100 ohms?

In the times of that TAS LOMC cartridges evaluations the specific cartridge loading never was associated to capacitance .

The advise is almost useless because we don't have or can have control on it to make any kind of changes about.

The cable manufacturers does not give the capacitance value but the tonearm manufacturers neither with the tonearm internal wires.

I don't think that that kind of advice from your part is of any help but only making more " noise " in the audiophile minds.

I always read your posts because always have very good contributions but for me not this time .

Now, always is good to have contributions as the wyn one. Don't you think?
I'm not technical oriented at your level but I always try to make things in the best way and in an easy way because at the end what I and we want is to enjoy the MUSIC and always is system dependent.

R.

Thank you for the nice words, Raul.

As far as the usefulness of an understanding of LOMC capacitive loading is concerned, for one thing it has provided guidance to the OP as to which of the two settings of the capacitive loading switch on his phono stage is likely to provide best results. And that in turn perhaps saves him the trouble of having to evaluate a number of different resistive loading settings twice, once for each of the two capacitance settings.

And the experience reported by Catcher10 certainly serves to illustrate that knowledge of this issue can be helpful to other audiophiles as well.

Finally, while I certainly agree with your concluding statement that...

... I always try to make things in the best way and in an easy way because at the end what I and we want is to enjoy the MUSIC and always is system dependent.

... in a hobby where a lot of audiophiles concern themselves with dubious and unexplainable minutiae such as which way a fuse is oriented an explainable and potentially significant phenomenon such as this seems to me to be a reasonable thing for audiophiles to be aware of.

In any event, thanks again for the nice words.

Regards,
-- Al

Wyn, I note the the simple expedient of putting the 2120 Hz filter first has the effect of reducing RF by 50dB at 1MHz at the first device. Is it your view that an additional pole is required?

Thanks!

@almarg 
... in a hobby where a lot of audiophiles concern themselves with dubious and unexplainable minutiae such as which way a fuse is oriented an explainable and potentially significant phenomenon such as this seems to me to be a reasonable thing for audiophiles to be aware of.

Good Lord, Al, that's physics! It strikes at the heart of all that we stand for! Say 4 Hail Snakeoils and depart!

Use your ears....get the sound that pleases you.   I use 1000 ohms on my Ortofon. 

Whether to use the extra pole is an interesting question.
So, here is some more information, and a repeat of some old information so you can judge for yourself.
1. The additional pole serves not only to reduce the RF but also to reduce the deviation in the RIAA stage noise transfer function at high frequencies. Effectively the noise from the circuit peaks higher than it should at supersonic/lowRF frequencies.  This might not be a problem, but then again any non linearities in the amplification system might serve to mix the noise down to audio bands so why have it?
However, it does come at a small cost as the extra input pole 
rolls the RIAA stage off, making it flat to extended frequencies but does not compensate for the roll off that may be introduced due to a sub optimal loading on the input stage- basically you are tweaking the Q of the input stage load to flatten the response at 20kHz and that is hard to do.
2. Don't forget the MC mechanical characteristic may cause a significant peak. Reducing the input stage Q to be essentially a LR system adds a single pole low pass characteristic which, combined with the resonance, may produce a characteristic that for example might be +/- 1.5dB 20Hz-20kHz with a dip in the 4-10kHz region rather than -1.5dB (due to a 20Hz infrasonic roll off)  to +3dB (due to the resonance peak). 
3. The recording process (particularly analog) imposes restrictions in the frequency response- limiting the HF and LF responses. These restrictions are not set in any standard and are usually due to limitations in the equipment used (Tape recorder and lathe frequency responses and dynamic ranges for examples). Good recording engineers try to minimize the effects, but they still exist.

If you are like me where my HF sensitivity has been reduced by age etc. where I really can't hear above 13kHz, but my response is still excellent below, including down to 20Hz, then making sure that things remain flat to 10kHz or so is what really counts. Thus, over compensating the response to make the measurements have a minimal deviation from nominal over the "full" audio band is probably not the best approach.
Again, listening is best, but be careful not to delude yourself. 
Audiophiles (myself included) tend to get seduced by what are essentially deviations from what the real listening experience provides- such as excessive detail, ability to resolve supposed room artifacts etc. etc. 
These effects, in my substantial experience of live performances, just do not exist in a live listening environment, but what really matters are things like instrumental timbre and dynamics (both micro and macro) and that often gets lost in the shuffle, and in the recording.
Yes, others have emphasized this last point in this thread, but it bears repeating.

Dear @almarg  and friends:  """  Thus, over compensating the response to make the measurements have a minimal deviation from nominal over the "full" audio band is probably not the best approach.
Again, listening is best, but be careful not to delude yourself.
Audiophiles (myself included) tend to get seduced by what are essentially deviations from what the real listening experience provides- such as excessive detail, ability to resolve supposed room artifacts etc. etc.
These effects, in my substantial experience of live performances, just do not exist in a live listening environment, but what really matters are things like instrumental timbre and dynamics (both micro and macro) and that often gets lost in the shuffle, and in the recording.  """

""" Unfortunately accentuated dynamics and resolution all too often mean a really nasty peak at the HF. In my experience, getting a good test record and testing the RIAA response can be a real eye opener. """

As I said the contribution by @wynpalmer4 was and is an audiophile lessons for those that are willing to learn as me.

Both fragments/high ligths from the wynpalmer4 are ( for me ) the crucial/critical subject for all of us ( again for the ones that are willing to change. ).

The ones that read or seen my posts in Agon knows that I always ( form some years now. ) posted ( with different words ) exactly what we can read in those high ligths and almost all of you posted that I'm " wrong " but almost neves said why.

I like to learn every single day because it's what can confirm or not that what I'm doing or thinking is wrong or rigth.

As I posted I don't have the technical level of wyn or Al so those great contributions are for me as true " oasis " in the desert.

Yes, to learn we have ( at the same time ) willing to change willing to start with some system tests willing to start again with system evaluations willing to make a check up of our MUSIC/sound priorities because as happened to me many times those priorities are way wrong even if we are " jumping " of hapiness for what we are listening for months/years.

And remember that all of us have high ignorance levels in many audio regards and in other subjects that ignorance level is lower.

Through the wyn posts I learned that what I was thinking/posting over years was and is true only that I never had how to prove it. Thank's wyn.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Hi Al,
so, let’s look at some simulations of the RIAA stage input.
Let’s assume that a minimum capacitance has been achieved of 100pF, which as it includes the cartridge winding capacitances, the internal wiring of the pickup arm, the interconnect to the preamp, the wiring to the preamp input and the preamp input capacitance. is probably optimistically low and beyond absurd for anything that involves a SUT or a tube amp. Let’s also assume that mechanical resonances do not exist and the only thing that matters is the electrical response.
Let’s also use our ideal MC cartridge with 5mH and 5 ohms series resistance and lets start with a 47k load.
The peak is at 663kHz and the magnitude is 28dB, the 10MHz rolloff (relative to 1kHz) is 48dB, the boost at 20kHz relative to 1kHz is 70mdB.
For RFI- conducted RFI is generally c. a few kHz to 30MHz. Conducted RFI can be converted to radiated RFI in the power cords, power supplies etc. Radiated RFI is generally considered to be 30 MHz and above, except where conversion occurs. What domain are we concerned about?
I’ll choose the loss at 10MHz as a metric.
OK, lets increase the capacitance to 1000pF, which is a realistic cap based on the values originally presented as available, and see what happens.
The resonant frequency decreases to 223kHz, the magnitude drops to 26dB, but the 10MHz roll off is now 65dB! The gain at 20kHz is 68mdB.

Which of these would be more benign to RFI while keeping an acceptable audio response? I would argue the 1000pF case.

Now lets change the load R to 1k.
In the 1000pF case the peak is c. 3.5dB, and, of course, the loss at 10MHz remains the same at 65dB. The 20kHz boost has decreased to 53mdB.
In the 100pF case the peak has gone and the gain is now 4mdB and the -3dB bandwidth is about 400kHz. The 20MHz loss is 48dB.
Again, the 1000pF case is better from an RFI perspective, provided you don’t care about a 49mdB increase in RIAA error at 20kHz.
Now change the R to 100 ohms. For the 100pF case the gain at 20kHz is -1.3dB and the 20MHz loss is 51dB.
For the 1000pF case the 20MHz loss is now 66dB, but the 20kHz loss is slightly less than the 100pF case, so it appears that a bigger cap might be better, so lets try that.

Increase the cap to 10000pF. The 20kHz loss is now 0.8dB, and the 20MHz loss is 77dB!
Now increase it to 28600pF- the error at 20kHz is now 0mdB, the attenuation at 10MHz is -77dB, and the -3dB point is c. 40kHz which is generally at about the limit that the cartridge manufacturers specify.

So which of these scenarios gives the flattest 20-20kHz ELECTRICAL response AND the highest rejection at 10MHz?
And who knows, a real cartridge might actually have a slightly more ideal audio frequency response with a small loss at 10kHz and a larger one at 20kHz, depending on where the mechanical resonance lies.
By the way, I am the owner of two Miyajima Madake cartridges, one that’s approaching end of life and can’t be retipped and a second one with 12 hours of play, and I’ve been going through this exercise with them both with a SUT/tube amp combo and the AD797 based preamp and it’s proving very hard to reach a conclusion as to what is best...

Wyn

Oh, and I just wanted to say- the Miyajima Madake cartridge designer effectively loads the cartridge at effectively 60 ohms (I know as we have exchanged emails on the subject) using his in house SUT and amps and doesn’t add any cap in parallel- he prefers the sound. This is not the same as the recommended load which if I remember correctly is c. 200 ohms //0.68uF which I believe gives the "best" measured frequency response.
Some people (reviewers) claim that the Madake is best into a 1k or 10k or even a 47k load and I disagree totally- even though we all love the cartridge- so what is truth?
The units that I have are, if I remember correctly, #106 and #261 and they sound a bit different- the new one has a little less bass and a more strident HF and doesn’t measure quite as well as the older one which has c. 350hours of play, so hopefully it will break in and perform like its venerable ancestor does :-)

This is nonsense to ask other people what is the optimal loading for your own cartridge. Everyone's free to choose. 

Why is it nonsense? I know that I started out by seeing what others were loading the Madake with and it was seeing the huge range of answers that was posted that, to some extent, triggered the analysis process that I have gone through. 
If you view the cartridge as essentially a musical transformer taking what has been transferred to disk and producing a sound that you like then that is one thing, but if the idea is to, somehow, transfer the information from the disk to your ears in as perfect, unmodified, a way as possible then that is something entirely different.
At the very least, you'd think that getting something close to a decent conformance to the de-emphasis characteristic that corresponds to the original recording pre-emphasis would be a decent start, but as should be obvious, that is not so easy to achieve and some understanding of the limitations and trade offs in the choices that need to be made would seem to me to be valuable and I commend the original requestor for initiating this exchange.

I posted the thread. If its nonsense..stop reading it. I have learned a lot about the subject thanks to all the contributors.

What is nonsense is when you don't ask. Where on earth would you inform yourself regarding cartridge loading?

These forums are an amazing asset to those of us who want to learn more. 

I truly appreciate the patience and wisdom that have been shared in this thread.

Hi Wyn,

Thanks for providing the excellent and thought-provoking analysis. I see no flaws in it as far as it goes. And in fact the manual for the OP’s phono stage states that the higher capacitance setting (570 pf) can sometimes be beneficial with respect to "interference rejection," when used with LOMCs.


However I believe what underlies the differing perspectives between your analysis and what I, Atmasphere, and JCarr have maintained is that while your analysis focuses on rejection of RFI per se, as reflected in your choice of 10 MHz in the analysis, I and the others have focused on energy that may be generated by the cartridge itself, at and near the resonant frequency. Not directly in response to musical information, which is presumably not present at frequencies of hundreds of kHz and above, but rather in response to "surface noise," tics and pops, and other causes of unwanted high frequency modulation of the output of the cartridge. Or (and I’m just speculating here) perhaps as a result of upper order harmonic distortion components that may be generated by the cartridge in response to musical information at lower frequencies.


As Atmasphere stated in a post in this thread on 5-21-2018:

... the cartridge inductance combined with the tone arm cable capacitance forms a tuned RF circuit- which is energized by the cartridge signal. It can be over 30 db higher than the phono signal- thats about 1000x more powerful!

Note the words "which is energized by the cartridge signal."

I guess the bottom line, though, is that as is usual in audio there are many complexities and competing tradeoffs involved, as well as many system dependencies, and consequently there are multiple paths to an optimal setup, and multiple paths to setups that are less than optimal to varying degrees.

And speaking of complexities and competing tradeoffs, your mention of SUTs certainly brings many more into play. As I’m sure you realize, optimal loading with a SUT will usually be different than when a cartridge is driving an active circuit, in part because of the need to optimize loading of the transformer itself, to minimize ringing and resonances. Another consideration being that capacitance that is present on the secondary side of the SUT will be presented to the cartridge multiplied by the square of the turns ratio.

BTW, was the AD797 one of the integrated circuits you mentioned having designed? If so, or even if they were anything comparable, I’m truly impressed!

Best regards,
-- Al

P.S: @terry9 ;-)

No, I did not design the AD797. That was Scott Wurcer- a colleague at ADI and, incidentally, for whatever it's worth, also an ADI design fellow. However, I know the design quite well.
He and I were colleagues in the opamp group in the 80s. He focused on high performance relatively low frequency opamps such as the AD712 and then the AD797, amongst others.
I focused on high performance high speed amps like the AD843, 845 (at one point an audio darling), 846 (also a transimpedance design with some very interesting design aspects that I gave an ISSCC paper on) etc. etc. mostly using a complementary bipolar process that I helped develop that I believe was also used in the AD797. I also did things like designing the FET based AD736/737 RMS-DC converter and others.
I moved on to more RF, disk drive read/write, GSM, CDMA etc. transceivers, signal processing, PLL and DSP designs. 
Anyway, what the heck does "cartridge energy" actually mean?
It's an electromagnetic transducer that I grant you has a fair degree of non linearity (which is one of the reasons I like the Madake- it's quite low distortion for a cartridge and why I have ML Monti loudspeakers as most loudspeakers have far too much distortion for my taste) so it generates a voltage and has an output impedance.
I can vouch that the Miyajima cartridges respond to ticks and pops just about as you would expect based on their frequency response and the amplitude of the signal generated, so no alternative explanations are necessary. Are you perhaps stating that the increased current generated by the lower resistive load increases distortion? If so, I can say that I believe that it's not true for the Madake as I've measured IM and harmonic distortion under varying load conditions (Ah the joys of test records)- and they are really sensitive to cartridge alignment but not that I can tell, to  load.
And yes, I'm well aware of the SUT impedance transformations- and I also model them, although imperfectly, in LTspice, which uses calls to set up the parameters.  This can be quite insightful, for example are you aware of the LF response sensitivity to winding inductance? 
One of the "joys" of being an IC designer is the compulsion to measure/model everything! However, once the skills are developed it's relatively easy to do as long as someone else has done the hard work of producing suitable models to use.
Constructing an electrical model for the Madake was fraught with concern as using my own meters to measure the capacitance and inductance was anxiety producing.
Then when I plugged the parameters into the simulation and compared against my measured output I realized that the actual response had precious little to do with the electrical characteristics and everything to do with the mechanical resonances.
And so, the journey began...

Are you perhaps stating that the increased current generated by the lower resistive load increases distortion?

No, I was not saying that or implying that. And for that matter I have no particular knowledge of how the distortion performance of phono cartridges tends to vary as a function of load impedance.

Regards,
-- Al

Thank you, Wyn. Food for thought - or rather, food for experiment. Another pole means another stage and another pair of complementary devices, so the trade-off is obvious. But next is the amplifiers' turn, so it will have to wait!

Thanks again for your insights.

Dear @krelldog : I posted several times in this thread each one ignorance levels where some people has higher when other lower in this specific subject but additional to that there are all over the world ignorants that additional are in the stupidity are because can't understand that or those or anything on audio.

My attitude is always try to help for any one ( including me. ) trys to low those ignorance levels but I always ignore stupid persons because will never learn.

R.

Dear @almarg : "   I’m truly impressed! ".. With all my respecto to you and other enginners the " best " ones are/were the ones designers inside Analog Devices, B&B/TX, in the past National and so on and Wyn belongs to them.

They made and make only true industry reference designs/items, they write the " standards " about through their work, their first hand experiences  put all them in a league " orders of magnitud " above we  mere mortals. Especially me.

@wynpalmer4  I really hope you can stay with us at Agon. Welcome a board.

R.

@krelldog it's endless thread, good if you learned something, but it's obvious that you can only TRY differend loading to find what YOU like the most, not other people. As been said there is no harm for your cartridge to try whatever loading. If you prefer to read instead of listening then it's very specific way to learn. Practice is more important. This is why it's nonsence to ask what other people like when it comes to loading, simply becase you system does not sound like other people systems. For example you can prefer loading "X" with one amp/speakers and loading "Y" with another amp/speakers.  

Your right...and the reading led to practicing. I was clueless before I posted the thread.
I bought my Plinius Koru when I bought my current cart-Ortofon Quintet Black. Ortofon recommended me loading the cartridge at 20 ohms. I had a 22 ohm load setting and thats where I set it.
My soon arriving Ortofon Cadenza Bronze recommended loading at 50-200 ohms...I was just looking for a little direction....thus the thread.
I'm glad I posted it....I got some great feedback.

Actually, adding an additional pole can be as simple as finding a bias/protection resistor in series with a high impedance node in the signal path then adding a shunt cap to ground. For example, in the AD797 opamp based MC phono stage in AudioKarma there is a second opamp that actually performs the de-emphasis and it has a 390 ohms resistor in series with the non-inverting input that also is in the signal path from the first gain stage. 
The resistor is there mostly to minimize offset in the second stage. Adding a 3300pF cap to ground from the "output" end of the resistor improves the RIAA compliance and also improves the RFI immunity of the second stage. Many LOMC preamps have a non-inverting gain stage followed by a non-inverting RIAA deemphasis stage and the changes can be readily made. 
The second stage has much lower overload margins than the first stage due to the fact that it has boosted signal levels, especially in the bass.
Also, If it is non-inverting, the gain at HF of the second stage is asymptotic to unity so that, without the additional pole, the level of RFI well above the audio band is the same as that at the output of the first amplifier stage.
However, the overload margin is lower and the desired signals are much larger, so the chance of RFI causing a significant amount of intermodulation which can become audible is higher than in the first stage.
Incidentally, passive de-emphasis stages, placed between the amps which are operated in fixed gain, usually are better in this regard as they don't have the implicit HF zero that forces you to add the extra pole.

Wynpalmer4:  (or anyone else that might have an opinion for that matter)

I am curious to know what your thoughts might be regarding current mode phono stages that use a low impedance input that supposedly presents almost a short circuit to a moving coil cartridge.

My Aqvox does this so loading is literally taken entirely out of the equation as it is not possible to adjust loading in this mode. According to designers/manufacturers of phono stages this approach results in better performance.

Your thoughts on why this may or may not be a good idea?

Wyn, your coaching is much appreciated. However, I am running discrete differential amplifiers (MATxy devices) throughout, and there is no "bias/protection resistor in series with a high impedance node in the signal path". Also, I am using air or vacuum capacitors exclusively in the signal path, and so virtually any cap, let alone a 3300pF cap, is a non-trivial intrusion into available volume.

Also, I hear no signs of the problems discussed. Pops and ticks are mostly absent and unusually nonintrusive, even on 'good' grade records. So, for now, will leave the phono/pre alone. Thinking about direct driving my ESL's, for instance - do you have any thoughts about appropriate devices?

Thanks again for your interest.

The idea of driving a cartridge directly into the virtual ground of an amp either just using the amp input impedance (such as a grounded base transistor) or via a resistor is hardly a new one. Some of the earliest solid state phono stages did exactly that, including one that I sold in the UK in the 1970s. I also used a transimpedance op amp that I designed (the AD846) in that mode- using the device as a current conveyor and operating it both closed and open loop as the extraordinarily high impedance "compensation node" could be loaded by a resistor to provide a fixed, and low, transimpedance for the stage. 
I can't say that either approach seemed to be particularly successful.
A good way to view this is to simulate the response of the current from a cartridge model loaded in exactly this way, which basically means reducing the load R to whatever the amp input impedance is and measuring the current through that R- the assumption being that the current through the load R is what enters the ideal current conveyor.
It should be immediately obvious that the signal current is just whatever the voltage is across the resistor divided by the value of the resistor so it's just a scaled version of whatever voltage the original voltage amp saw and there is no difference in the output!
So, all we need do in the original design is to reduce the cartridge load R further from the 100 ohms and see what happens.
Let's return to our initial case- the one with 100pF, not the one that is "optimized" with a much larger cap- clearly as the resistor falls in value the effect of the cap is reduced so it seems like a good place to start.
Remember at 47k load the response is extremely flat in the audio band but has a screaming peak at c. 700kHz.
To get a decent noise performance a bipolar input stage needs to run at  least at 1mA current, and lets also assume that the input is complementary- NPN and PNP transistors with the emitters connected, both in a common base configuration- then to a first order the input resistance is about 10 ohms.
Under these circumstances the frequency response of the input current or voltage for our 5ohm 5mH cartridge is down c. 13dB at 20kHz! That doesn't seem so sensible to me.
The reason for this should be obvious. The generator output impedance is dominated at HF by the winding inductance so it increases c. linearly with frequency beyond the Rint/ ZLint point which in our case is 2*p1*5/.0005=2000pi=c.2.8kHz!
As far as the cartridge is concerned it can't tell whether the load it sees is into a common base configuration with zero dc offset, or the same load into ground. By the way, the DC offset needs to be zero. Running DC current into a cartridge is just not a good idea...
You could reduce the input bias current or add an extra R to make the load resistance go back to 100 ohms- but why is it different from the case with the voltage amp?
Yes, common base stages are different insofar as the stage is "broadbanded" compared to a common emitter transistor stage, and the collector base capacitance is not multiplied by the collector- base voltage gain (Miller capacitance)  but I don't really see why that is a big deal- indeed if you really care then just cascode the input stage and reduce the Miller capacitance that way- something that is often done anyway as it improves the bandwidth/linearity of the input stage.

Direct driving your ESLs? 
I'm sorry, but I don't know what you mean.
I use Rogue M180s to drive my Montis, which is interesting as the Montis are, of course, capacitive above the woofer crossover with an impedance of, if I remember correctly, 0.9 ohms real at 20kHz (the minimum) with the input looking inductive after that, and the Rogues are inductive with an output impedance, again if I remember correctly, of about 0.33 ohms resistive at mid frequencies rising to 0.9ohms inductive for the 4 ohm tap at 20kHz. It was interesting to simulate the response and add models for the interconnect wires which I measured for resistance, capacitance and inductance. The best turned out to be short (less than 2m), multi (3 or more) parallel 12 gauge wires. Fancy cables didn't add anything that I could determine.
Extra inductance or resistance always was worse. Extra capacitance didn't seem to matter- which is hardly a surprise.

May I ask what low output MC cartridge has 5ohm and 5mH? The 5ohms is representative enough, but 5mH is a few decimal places larger than I would expect.

http://www.whatsbestforum.com/showthread.php?15077-Cartridge-Loading-A-Misnomer&p=258578&viewfull=1#post258578

Sorry, a typo. It was meant to be 0.5mH. The simulations were all done with 0.5mH- note that the roll off calc for the RL was done with .ooo5H. I can perform the sims for any set of values you choose, and if you care to do so I would be obliged to you.

I just measured a cartridge I have it's 10.7uH, 16 ohms DC.
I'll resimulate with that and see what happens.

I measured the inductance- cartridge plus interconnect to phono input on preamp.
The total was 11.8uH. The capacitance was 51pF. including the preamp input the capacitance was 205pF. Excluding the input load cap it's 85pF.
I'll use those numbers and see what I get.

Thank you for joining the thread, Jonathan, and for providing the link. The text to the right of the last figure in the post Jonathan linked to is particularly relevant. Some excerpts [words in brackets are mine]:

The resonant peaks have too high of a frequency to hear directly, but the magnitude of the peaks and their high frequencies are likely to cause decreased stability and increased distortion and noise in many phono stages. Some phono stages will be fairly insensitive to these ultrasonic peaks, while other phono stages will show bigger effects....

... No additional capacitive loading was used [in the simulations] at the phono stage input.

Comparing the simulations of the 3 cables shows that higher capacitances of the tonearm-to-phono stage interconnect cable demand lower resistor values at the phono stage input to control the resonant high-frequency peaks. This, in turn, reduces the cartridge’s dynamics and resolution, and can also worsen tracking ability.

Also, regarding Wyn’s simulations, I would reiterate a point I made in an earlier post:

Almarg 5-26-2018
I believe what underlies the differing perspectives between your [Wyn’s] analysis and what I, Atmasphere, and JCarr have maintained is that while your analysis focuses on rejection of RFI per se, as reflected in your choice of 10 MHz in the analysis, I and the others have focused on energy that may be generated by the cartridge itself, at and near the resonant frequency.

Best regards,
-- Al

With the measured cartridge/minimum input cap (85pF) the response with a 47K R has a 29dB resonant peak at 4.3MHz and is -12dB at 10MHz.
With a 1k load it’s 4.2MHz and 9.5dB.
With 250 ohms it’s basically flat to 5MHz, with -14dB at 10MHz.
with 100 ohms it’s 1mdB down at 20kHz, with -17dB at 10MHz.
Let’s change the cap to 205pF, the original total input cap.
-1mdB at 20kHz, -20dB at 10MHz.

Now 1000 pF. 0mdB at 20kHz, -32dB at 10MHz, 0.5dB peak at 1MHz.

Now 10nF. 10mdB at 20kHz, -52dB at 10MHz, 3dB peak at 400kHz.
Now 22nF. 20mdB at 20kHz, -59dB at 10MHz, 2.2dB peak at 270kHz.
Now 47nF. 27mdB at 20kHz, -65dB at 10MHz, 0.8dB peak at 147kHz.
Now 0.1uF. -12mdB at 20kHz, -72dB at 10MHz. No peaking, -3dB at 150kHz.
And the actual load used by the designer, with an estimated cap based on the SUT ratio and a tube input stage of my knowledge.
+7mdB at 20kHz, -50dB at 10MHz, 1.7dB peak at 400KHz.
The same, with the recommended load cap of 0.68uF added.
-3dB at 20kHz, -87dB at 20MHz.
Incidentally, by my measurements the cartridge peaks by c. 5dB at 20kHz due to the cantilever resonance, so the extra cap makes the response more symmetric about 0dB, but at the cost of a dip close to 4kHz, which is not a great tradeoff in my opinion, so it’s no wonder the designer prefers to have no cap.

Personally, I’d go for the 100 ohms, 0.1uF load if I was using a non SUT input and 60 ohms no cap if using the SUT, which sounds about right.
Let’s now look at the driving into a low impedance current conveyor node case.

The lower inductance of course changes the R/L ratio by about a factor of 45, so driving it this way is more plausible.
However, a shunt cap between the input node and ground still would be beneficial as far as RFI is concerned.
For example, with the 10 ohms mentioned before the 20KHz loss is 14mdB and 10MHz is -29dB with 85pF, but with 1000pF it is still only 14mdB at 20kHz and -30dB at 10MHz.
With 0.1uF the loss is 17mdB at 20kHz, and at 10MHz it’s 65dB.
Personally I’d go with the 0.1uF cap in this case.

By the way, I still have no idea what you mean by energy of the cartridge itself etc.

By the way, I still have no idea what you mean by energy of the cartridge itself etc.

I didn’t say "energy of the cartridge itself." I said energy "generated by the cartridge itself," and I was referring to energy "generated by the cartridge itself" at RF frequencies. Which I was distinguishing from Radio Frequency Interference, which appeared to be the focus of your analyses.

Surely it must be more than obvious to you that a cartridge generates an electrical signal when it is playing a record, and electrical signals contain energy, and:

Energy = Power x Time

And for a resistive load:

Power = Voltage x Current = Voltage Squared / Resistance = Current Squared x Resistance

Not sure why what I meant by energy "generated by the cartridge itself" would not have been clear.

Regards,
-- Al

OK. Thanks for defining what you mean. So lets look at power.
I ran a simulation and calculated the power dissipated in the cartridge series R and the load R and plotted what happened to the total power as the load cap is varied.
The voltage and current must be in phase for a resistor so power remains V^2/R. We know that the voltage across the load R is reduced as the cap is increased- after all, that’s the objective- so the load power must fall- but what about the series R? I calculated this and added it to the load power to get the total power.
So, back to the "real" case with a 11.8uH winding inductance , 16 ohm Rcart, 85pF load and 100 ohms. I set the input to 1v rms and calculated the total power in the two resistors =10*log(((voltageacrossRcart^2/16) +(voltageacrossloadr^2/100))
The power plot starts at -20.6dB at LF then falls by 3dB at 1.7MHz and by 18dB at 10MHz. No peak is present.
I then changed the cap to 0.1uF.
The power at 1kHz was -20.6dB, it peaks at -13dB at 150kHz , is 3dB off the peak at 87kHz and 320kHz, then falls monotonically by 25dB at 10MHz.
So we’re measuring 1/7 the bandwidth and a bit less than 6x the power in that bandwidth- which is, again, hardly surprising, so the power is more or less constant, but the total power at 10MHz is reduced and the load power at RF is hugely reduced, so isn’t that better?
Is the increase in power dissipation in the cartridge at supersonic but not RF frequencies problematic?
Darn! I wish I had some way of showing plots.

Wyn, I'm not claiming anything original here, except perhaps my anal-retentive dedication to costly devices!

Speaking of which - direct drive ESL. I have new generation Quads, which I opened up as soon as the warranty expired. I found a step-up transformer for each stator, cheap WW resistors and ceramic caps with their high dielectric constant. Obviously, all of these had to change.

As you seem to be an owner of ESL's, obviously you know that the step-up transformer tends to ring unless the input is coupled through a resistor. I changed the step-ups to a toroidal device which drove both stators, requiring an input resistor of about an ohm, which is a natural place for nichrome wire. Since I needed speaker cables anyway, I thought,"Why not use the nichrome wire for both purposes?"

Now I am thinking of high potential amps driving the stators directly, without any step-up device. I was wondering if you knew about HV transistors, and if you could save me some time and some angst with awful prototypes. That's all.

Well, I once was the proud owner of a couple of quads- the original ESL-57 and a pair of ESL-63s that I also pulled apart- their delay line/filter design to drive the annular segments was quite neat. However, I had serious reliability problems and I switched to Martin Logans and I've stayed with them ever since. I have Montis in the main audio room and a pair of venerable Prodigies in the home theater room and I've never had a problem with either of them.
Yes, I am aware of the fundamentals of their operation, but alas not the details so I really cannot help you out in this. Frankly, I'd be pretty leary about shipping the needed HV to the speaker from an external amp. Visions of lethally shocked dogs, maids, and kids spring into my mind. Having said that I believe that at one time Acoustat built ESLs without the transformer, instead using built in output transformer free tube amps

Your cautions are accepted. I've been thinking mil spec circular connectors and cables encased in grounded shields, or mono blocks bolted to the back of the speaker bases.

Interesting parallelism. I went from Magnepan to ESL-57's to Prodigies to 2905's. That's been an 'absorbing state' for 15 years now.

Thanks for providing the comprehensive simulations, Wyn.

Regarding:

Now 1000 pF. 0mdB at 20kHz, -32dB at 10MHz, 0.5dB peak at 1MHz.

Now 10nF. 10mdB at 20kHz, -52dB at 10MHz, 3dB peak at 400kHz.
Now 22nF. 20mdB at 20kHz, -59dB at 10MHz, 2.2dB peak at 270kHz.
Now 47nF. 27mdB at 20kHz, -65dB at 10MHz, 0.8dB peak at 147kHz.
Now 0.1uF. -12mdB at 20kHz, -72dB at 10MHz. No peaking, -3dB at 150kHz.

Am I correct in interpreting that these results are all with a 100 ohm load resistance?

If so, and given these results:

With the measured cartridge/minimum input cap (85pF) the response with a 47K R has a 29dB resonant peak at 4.3MHz and is -12dB at 10MHz.
With a 1k load it’s 4.2MHz and 9.5dB.
With 250 ohms it’s basically flat to 5MHz, with -14dB at 10MHz.
with 100 ohms it’s 1mdB down at 20kHz, with -17dB at 10MHz.

... It appears to me that these and the rest of your results are reasonably consistent with statements I, Atmasphere, and JCarr have made, and with what is illustrated in the plots provided in the post Jonathan linked to, that in the absence of a relatively heavy resistive load a large resonant peak will occur at an RF frequency, and (as can be predicted theoretically) at progressively lower frequencies as the amount of capacitance increases.

But as your simulations show, even if extremely large amounts of capacitance are present, e.g. 1,000 to 100,000 pf, a load resistance in the vicinity of 100 ohms will cause frequency response to be reasonably well behaved, at least for the particular cartridge parameters you chose.

However there is only one phono stage I am aware of which has an input capacitance within that very high range, that being the AcousTech PH-1, which in LOMC mode provides a load of 100 ohms in parallel with 10,000 pf. I believe that the great majority of other phono stages having active input stages have input capacitances in the area of perhaps 50 to 250 pf or so. I would expect that there are reasons for that.

And I would expect that in many cases those reasons, in addition to making it possible to provide a wide range of choices of resistive loading, are along the lines of what Jonathan has said in the post he linked to. Namely that heavy resistive loading "reduces the cartridge’s dynamics and resolution, and can also worsen tracking ability." As well as what I quoted him as saying in an earlier thread here, namely that "less capacitance allows the resistive load on the cartridge to be reduced, which will benefit dynamic range, resolution and transient impact."

Perhaps he or Ralph (Atmasphere) will elaborate on that, as they are much more expert in this area than I am.

Regards,
-- Al

What I don’t understand is why any of the purported 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 I would think. As for the rest, well, take the Madake for instance- the resistive load that people (reviewers) claim is best literally varies by nearly four orders of magnitude! I load mine with 60 ohms (as do many users) and I find that the resolution and dynamics is excellent while maintaining a natural timbre, tonal balance and micro/macro dynamics while not creating the unnatural etched image that many "high resolution" MC cartridges produce.
In any case, I’ll have to research this to see what technical white papers or similar exist on the subject.