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."
Cartridge Loading.....Part II
I read last night the below noted discussion with great interest. It's a long post but worth the effort and I found it interesting.
It started me thinking about the amount of loading on my moving coil cartridges. Years ago I purchased my first MC Cart, a very nice Benz Micro Glider, medium output of 0.5 mV as I recall. At that time I inquired about loading here on Audiogon. I was convinced, via discussion, by another member, that 300 Ohms was the magic number, so I thought.
Time moved onward and my second MC Cart is currently a Lyra Delos, again medium output 0.6mV. Both carts had Boron cantilevers', 6 nines oxygen free copper coils and line contact diamond stylis. When I set up the Delos I did not change or even consider 'loading' changes. That was a grand mistake.....
Well, thanks to this specific thread I started to second guess myself . (you can do this when retired and more time is on your hands....)
My take from this recent thread is as follows. Load at 100 Ohms or at 47K Ohms with a quality MC cartridge. I opened up my Conrad Johnson EF1 Phono Stage this afternoon. Found it set at 500 Ohms loading. 100 Ohms is not an available setting. Damn...All these years I've been running the wrong loading, and on two carts, back to back... I don't recall why I set the loading at 500 Ohms. Faulty logic.
I reset the loading to 47K, buttoned things up and called the wife in for a listening session. Sure as heck both of us noticed the highs were crisper and more 'apparent' than in the recent past. Not a huge difference, but yes, a difference.. Hard lesson learned!
So, you smarter folks on this site might banter amongst yourselves, but in reality there are those of us, behind the curtains, reading and listening! I just wish I hadn't wasted all those years listening to the incorrect load setting!
Ending with a sincere thank you very much!!
Lou
DeciBels refer to voltage, yes.
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.
|
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. |
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? |
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
|
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. |
@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.
|
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. |
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. |
@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.
After all those years why you did not learn or at least try to understand about that issue? sorry.
R.
|
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. |
The virtual ground doesn't care what the origin is of the impedance in series with the voltage source. An ideal virtual ground simply means that all of the current that enters a node is conveyed somewhere else with a zero change in the voltage at that node. An ideal opamp with infinite gain and bandwidth will be a perfect virtual ground, just as a perfect ground will have zero impedance to "real ground". From Wikipedia. "Lenz's law, named after the physicist Emil Lenz (pronounced /ˈlɛnts/) who formulated it in 1834,[1] says that the direction of the electric current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes changes in the initial magnetic field. It is a qualitative law that specifies the direction of induced current, but states nothing about its magnitude. Lenz's law predicts the direction of many effects in electromagnetism, such as the direction of voltage induced in an inductor or wire loop by a changing current, or the drag force of eddy currents exerted on moving objects in a magnetic field." To paraphrase, a changing magnetic field is created that opposes the changing magnetic field that creates it. That in turn will create a "restoring force" to oppose the motion that created it in the case of a cartridge. Lenz's law says nothing about the magnitude of that field and hence that force. That's a much more complicated exercise as there is no simple, closed form, equation for it. It can be estimated/approximated very roughly assuming some level of reciprocity, but I have no intention of going into the arcana of this. The point is that IT IS small compared to the mechanical forces being applied to the cartridge due to the reaction of the walls, and that it does increase as a function of increasing frequency. Incidentally, I don't intend to further participate in this exchange. |
Dear @dover : As always I respect a lot your opinions but what you are talking about me and my " audio life " trend certainly is far away to be reality. If that’s really what you think then you are wtrong about and let me explain you:
no I don’t confuse cantgilever material with cantilever motion, I’m with @intactaudio on that issue , if cantilever goes stiffer that’s is a good thing but if the cartridge suspension goes stiffer then that is way different and in no thread/posts no one named " cartridge suspension ". Wyn and PM proved that changes on loading develops IMD, as J.Carr posted too, but don’t cause mistracking and I agree ( not today ) but from several years now with.
@imhififan gaves me the advise to make loading changes tests and he and I did it. I did it with different cartridges and one of that cartridge was the Denon 103 that by coincidence was the one he choosed too and both of us with different room/system experienced no mistraking issues by loading changes.
I know perfectly the impact that loading has mainly in the phono stages and in way minor way the impact in LOMC cartridges. You are wrong about my phonolinepreamp that is designed with a really high headroom and is totally inmune of those poor designed phono stages even that my preamp frequency goes over 1.5Mhz. @lewm owns the same unit, please ask him. No I don’t need per sé to load at 100 ohms when almost all LOMC performs the better with that load, theory of loading cartridges is theor and we know that some times what theory says does not happens under play.
Wrong too that I prefer MM cartridges, it’s not that way. Several years ago and due that I owned some MM/MI cartridges that were in closet I decided to give a listen to it and then I discovered to me that with today room/systems MM/MI cartridges can play with high quality performance levels and from there came that very long thread on MM cartridges. In the other side ( maybe you born in audio with a LOMC cartridge in your hand. ) my very first cartridges in audio were all MM/MI that were the ones I re-discovered several years later and my first LOMC cartridge was the same Denon 103 that I used on the loading tests. In those times I owned Pioneer top of the line electronics and its HPM 900 speakers.
Btw, I posted several times that I’m not against the theory of that stiffer issue and I don’t want to add more comments about when all is done by the gentlemans that really has the knowledge high levels and first hand tests about even one of them made several tests in other thread in the same loading subject in real time because he has the modeling tools for it: yes that gentleman is Wyn. Can you do the same with the same knowledge levels? No one is perfect and certainly you and me are far away from there.
Btw, please don't follow try to hit me because you can't and I'm not like you and I'm not to start speaking of each of your system audio items you own, so stay calm and cool.
R. |
@wynpalmer4 The virtual ground is one thing when it is driven by a resistance in series with the input (which might be a cartridge). Its a bit different when the cartridge itself is that resistance. WRT actual ground, I think we can both agree that a cartridge driving a dead short will not produce anything that can be amplified. A virtual ground is different in that manner 😉 One thing that has come up in this thread is the mention of Lenz's Law, which has to do with the radiation of a magnetic field from a conductor when conducting. Its been brought up in the context of 'back EMF'. I've not been able to discern how this is supposed to work; if driving a loudspeaker (which has significant inductance interacting with a magnetic field) you do get back EMF but in the case of the cartridge an impedance (for the most part) very little inductance in the load is present. So I would appreciate an explanation; as best I can make out the back EMF would be insignificant WRT the source. |
I gave up when Raul confused cantilever material with cantilever motion ( see quote from Raul below ). The reality is that any change of loading will possibly have an impact on "tracing the groove". The Shure white papers explain this clearly with their testing on groove tracing and the impact of changes in compliance - at worst they describe scrubbing motion of the stylus/cantilever from mismatched arms/cartridges. It is the genesis of the use of their stabiliser brush. Tracking tests on records do not measure distortion - they only indicate a tracking ability ( crudely ). In my view there may be no obvious mistracking from altering the loading, but there is the possibility of a change in tracing and distortion ( for better or worse ). If Raul loads all MC at 100ohms, then likely he cannot hear the impact of changes in loading, or he has a low resolution system - or both. As an aside I agree with JCarr's and your comments that loading is more about taming poor quality phono stages with poor overload margins at ultra high frequencies. Folk need to understand that, like brick wall filters in early digital, problems at ultrasonic frequencies can generate artefacts down into the audible region. Perhaps Rauls home brew preamp is in this group which would explain why he needs to load all MC's at 100ohms - which is extremely low - particularly for cartridges with an internal impedance above 5-6 ohms. It's no wonder that Raul thought for years that he preferred MM cartridges most of which have large phase shifts and frequency aberrations in the audible region - necessarily tuned by loading R & C of course in order to get a reasonable facsimile of a linear phase coherent response.
|
For the record (if you see what I did there) I've never stated that loading a cartridge would cause mistracking! That is simply Raul with his usual logical fallacies again (in this case, the classic Strawman). What I have stated is that loading the cartridge will cause the cantilever to become stiffer. This fact is unavoidable as anyone grounded in generator and alternator theory knows. This does not mean that the cartridge will mistrack. It means what I said: the cantilever will be stiffer; whether that affects the performance of the cartridge is another matter and other than suggesting that it might affect high frequency tracing ability. I've also been careful to not state what frequency, which may well be ultrasonic; at any rate obviously is an unknown. Raul, in his on-going quest to simply make me wrong, has been trying to put words in my mouth. Fortunately I'm way to far away for him to actually do that 😁 |
Ok guys, I'm getting dizzy. @rauliruegas , I already have that test record! Channel D has received my wire transfer ($500 credit) and A friend says the Platinum Signatures will arrive any day. I might also get an Ortofon Verisimo., teeter tottering on that one. Since I can run the phono stage 4 different ways and I can record records to the computer I will be able to make 192/24 files of all the results which I can download so everyone can judge for themselves as long as your system can play files. If not then GET WITH IT. Digital is hear to stay (spelling intended). It allows you to do cool things you can not do otherwise and share the results with friends. @rauliruegas I have no idea what is better but I will figure it out and I will be happy to email you the files so you can compare. Then you can tell me! |
Dear @intactaudio " the possibility that heavy loading may actually reduce mistracking hasn't been mentioned or covered by anyone .."
I did it.Over the years participated in no less that 8 threads about cartridge loading here and wbf and in one of them I posted something as:
stifness of cantilever it's a good thing because cartridge designers normally looks for the stiffer cantilever material as Boron, higher stifness the better in favor of better quality level listening performance. Anyway, all is done.
R. |
Mijo, I agree that there is a big difference between loading @ 47kΩ and loading approaching zero. These two extremes very closely represent the "ideals" of current vs. voltage amplification. It may very well be conjecture but discussion of this on the most basic level is the only way to get a common solid foundation for everyone to build upon.
Interesting. Now the question becomes what was the cause of the distortion change? I see two possible options: 1: The distortion of the two modes of operation were different. 2: The effect of the radically different loads altered the behavior of the cartridge resulting in different measured distortions. Chances are the difference is some combination of the above two and simply removing the cartridge from the tests and using a sound generator should illuminate the differences between the two modes of operation. Repeating the measurements with a number of different cartridges should also illuminate if there is a specific pattern happening.
dave |
@intactaudio , I think miss-tracking distortion and IM distortion are two separate but additive issues. There is a big difference between normal cartridge loading and an impedance approaching zero. This is all conjecture (theory?) at best. I have not seen a study done on tracking ability vs cartridge loading. I have seen distortion measurements on the same cartridge run voltage mode vs current mode and distortion is certainly lower in current mode. I think this is me agreeing with @rauliruegas again. It is indeed a strange world. @rauliruegas , I will run the Seta in both modes with and without digital RIAA correction to see if I can tell a difference but it will be a while. Rob has told me my phono stage is 4 to 5 weeks away. I still have not cornered a cartridge yet. All the cartridges I am interested in are "special order" and it seems nobody is making anything at the moment. |
Cutting and pasting text without any reference to context is not proof. Where was it ever proposed that heavy loading causes additional mistracking? It has been my contention that exactly the opposite may be occurring. Everything you mention specifically refers to it being impossible for heavy loading to cause mistracking with which I concur. However the possibility that heavy loading may actually reduce mistracking hasn't been mentioned or covered by anyone beyond Moncrief that I know of. dave |
Dear @intactaudio : This is what I posted and pasted from what he posted and came from a years ago cartridge loading thread. The loading/tracking is not a new issue but an " old " issue discussed here and in other internet audio forums:
and here somerthing that he forgot to mention and that comes in that " old " thread that shows that that " myth " of tracking problems due to cartridge loading changes is a lie and nothing more:
""" 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. """ Btw, yes I have too that test LP and is logical that when we are mesuring/talking of compliance tracking always comes in the analysis. Cartridge compliance is so important that can " change " what we are accustom to do on the tonearm/cartridge resonance frequency issue that tell us that that resonance frequency must be in the 8hz-12hz ( around it. ) frequency range and the compliance has the " power " to does this: the LOMC Ortofon MC2000 model was reviewed in the 60?s by the Audio magazine, the cartridge was mounted in a Technics EPA 250 that was mounted in the Technics SP-10MK2. Well the cartridge weigth is 11grs. and the measured compliance was over30+ cu and along that tonearm its resonance frequency was as low as 5hz. Go figure ! and guess what : that tonearm/combination that in theory can’t run together had no single tracking issue with the true test Telarc 1812. Why that kind of success? because that really high compliance that gives that cartridge those extraordinary tracking abilities and I owned not one but 3 samples of that cartridge and you can be sure that at any loading will has not tracking issues. It’s impossible that loading can change the compliance in a LOMC cartridge in a cu levels that provoque added mistracking to the usual cartridge levels, no way. I’m not against that loading stiff the cantilever the real subject is that that stifness micro micro microscopic level that exist can´t be of the necessary magnitud to cause adding mistracking. As @mijostyn posted: silly to think in other way. Now, in the other side no one including the person that supports that till today never proved that added mistracking by changes in cartridge loading. I understand you but I think is useless and futile continue talking of something with out true prove. Don’t you think?
On other topic and thank’s to your last post that shows that Benjamin B. Bauer was the CBS laboratory Vice-president I learned that that Mr. Bauer is the same gentleman that in 1945 along names as Baerwald, Stevenson, Pisha and obviously Löfgren developed too equations/solution for tonearm/cartridge alignment: exist a Bauer alignment R. |
If we accept this to be the case (and I do) then the next logical step is to agree that we are simply discussing varying degrees of mistracking. Treating mistracking as black or white serves little purpose in this discussion.
Where is this proof?
In your stack of 20 test records I assume you also have CBS STR-100 which has a test for compliance. It is interesting to note that the telltale here is also mistracking. Again to repeat myself... If you accept that according to Lenz that loading a cartridge will stiffen the cantilever, how can that not effect the compliance? dave
|
Dear @mijostyn " did order an ultra accurate RIAA board but I am already set up to do digital RIAA correction. " If you have that ultra accurated inverse eq. RIAA why do you think you could need digital corrections to that accurated analog RIAA?
Maybe you know " something " that I don't " see " down there.
R.... |
Dear @mijostyn : Over several forums that person is atmasphere, yes silly.
@intactaudio , " The only answer I can come up with is mistracking. "
All cartridges no matter what has a mistracking issues always and in every LP recording. Sometimes and depending of the room/system resolution levels and the accuracy of the cartridge/tonearm alignment and set up we can be aware of some of those " mistracking " and normally we don’t.
In the other cartridge loading thread other gentleman and I with out been in touch made tests using the same cartridge making changes on load. The cartridge was a non very good tracker: Denon 103 and both of us in different room/systems and different loads can’t fin out any difference in what we were listening due to load changes.
In that thread I named some of the over 20+ test LPs I own where are those 2 you named here.
Wyn proved that loading does not affects the tracking cartridge abilities and JC says the same and we audiophiles tested and confirm it. What exist always is IMD issues but not for loading additional mistracking.
In the other side, think what you need to change the cartridge tracking ability with the effect to have higher mistracking levels ( everything the same ) and you will find that the parameter that needs to be changed is the compliance ( of course that VTF or AZ or VTA can do it too but everything the same compliance is the one. ) in the cartridge and for in true can exist a higher levels of mistracking maybe you need to change say 15cu in the cartridge to around 8cu-10cu ( and in this non-existent hypothetical example it will change too the tonearm/cartridge resonance frequency. ) and certainly load changes can’t do that not even can makes that compliance goes down from 18cu to 17.8 cu. Loading does not affect tracking/compliance in cartridges and certainly not FR that as said JC: " that’s bogus. Now, one thing is try to change compliance in static status and the other during playback because in playback all the stylustip/cantilever forces that provoque the spining of the LP grooves friction against the stylus ti are enormous/gigantic for any radical change of loading can disturb it and remember that the stylus tip is in continuous " jumping "/loosing contact with the LP surface. Loading does not change all those. Why the changes in measured IMD by PM? for other reasons but tracking issues. Btw, please makes this test several times: track the same LP grooves and measured 4 times in a raw and you will see that measures you took are different even that made with the same test grooves.
R.
|
A guy named Lenz observed and documented the underlying concept and I'd hesitate to call his work silly. Now extrapolating his work to cartridge loading is interesting. Moncrief showed decidedly different IMD results between the same cartridge lightly and heavily loaded. While I have not been able to replicate his results perfectly, I have seen several areas where loading effects the measured behavior of a MC cartridge. Stepping back and looking at the big picture One has to ask "What causes IMD sidebands from the record groove needle interface?" The only answer I can come up with is mistracking. A number of tracking ability tests exist. Tests like the Audio Obstacle Course use recored music with increasing levels of one selected instrument and the user can judge where mistracking happens. This is the closest we can come to a real world example but it is important to understand the results are subjective which makes the results unique and hard to relate to others. The other approach as used on the Shure TTR103 and the CBS STR110-112 is more scientific and requires the use of two tones typically 400hz and 4kHz and an intermodulation distortion measurement. Here is the blurb from CBS: The two things that jump out at me in the above are the use of the phrases "Instantaneous force" and "tracking distortion" both of which seem to be directly related to the topic at hand. The last bit about other system nonlinearities causing IMD is valid but outside the realm of the variable being tested here. (tracking force) If we agree that the load will as ralph states above:
It seems fair to follow up with the premise that this can also effect tracking ability. It is important to note that the extreme and clear results given by Moncrief do represent the two extremes where Rcart<<Rload and Rcart>>Rload which just happens to be the exact case of the ideal current mode vs. voltage mode input stage. dave |
@rauliruegas ,Don't worry friend, there is now a front panel switch that allows you to switch back and forth, no more jumpers. The Phono Stage has a 5 MHz bandwidth. I did order an ultra accurate RIAA board but I am already set up to do digital RIAA correction. Who came up with the thought that cartridge loading affected tracking? That is rather silly. Once you get to an extremely low impedance input there is less back EMF for certain. I have seen oscilloscope tracings showing this. I am not an electronics engineer. I can only rely on what I read and see and have to assume it is not marketing BS. I sort of doubt Rob Robinson is the type of guy to BS his customers. |
Dear friends : For some of you that read for the first time the Wyn posts here next I pasted what he posted several years ago in other cartridge loading thread:
"" 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.
and here somerthing that he forgot to mention and that comes in that " old " thread that shows that that " myth " of tracking problems due to cartridge loading changes is a lie and nothing more:
""" 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. """
R. |
Dear @mijostyn : After reading the Wyn posts are you still thinking of the current phono stage superiority over the voltage designs PS you supported?
R. |
A copy of a post I placed a short time ago...
I'm in the process of having a phono preamp made manufacturable by a well known audio company. The first thing they insisted upon was that the design would be implemented in SMD- purely for manufacturing purposes. This had it's own unique set of difficulties- for example, some of my preferred capacitors were not available on SMD, so a search for suitable items of a different technology (ceramic MLCC C0G vs Polypropylene film) was needed, together with a proof that the distortion characteristics were essentially equivalent. The other aspect was that the preamp design investigated two possible implementations, either a voltage mode input, or a current mode input, and with the 75uS RIAA TC implemented in the first stage. I ended up with a voltage mode input, as when designed for equivalent gain and RIAA characteristic there is, generally, no measurable or audible difference. However, there are indeed differences in operation and implementation. To put this somewhat in context, I designed a number of "transimpedance" amps while at ADI, most notably the AD846, together with a number of conventional opamps, so I am familiar with the concepts. The AD846 was designed to have almost perfect current conveyance properties and could be operated open loop as a transimpedance amplifier. Most opamps/amplifiers use negative feedback to achieve this goal, or have high distortion levels if operated open loop. As I don't want to make this into a "white paper" I'll try to be brief. 1. A phono cartridge is a voltage generator (Vs) with an output impedance which is mostly a resistance in series with an inductance (R+Ls). This can be converted into the Thevenin equivalent current source- which is a scaled current (Vs/(R+Ls)) with the output impedance in parallel to ground. If you take this current and drive it into a virtual ground, which shorts out the shunt components, and convey it to the load resistance (Rl) then the output voltage is Vs*Rl/(R+Ls). If Ls is small then the gain is completely dependent on the series resistance of the cartridge and will vary from cartridge to cartridge, and if LS is large there will be a HF roll off. Any shunt capacitance will be essentially ignored. If there is a resistor added in series with the virtual ground, then the current is shared between the equivalent shunt components and the series R, and the gain becomes even more variable. Voltage mode lacks this complexity. Provided the load impedance is relatively large compared to R the gain is easy to determine. However, the shunt capacitance is not ignored, but for MC cartridges the inductor is so small that all parasitic capacitance values are irrelevant, assuming the load R is small enough to damp out the LC resonance. Current mode does not experience this resonance, but correct loading Rs plus a phono stage with a suitably good ultrasonic overload margin will take care of the potential problem. MM cartridges into a virtual ground are not rational unless there is a very large resistor in series with the virtual ground. This is because the R is large but L is even larger.
2. In voltage mode the input stage is non-inverting and will experience potentially substantial deviations about ground. For many opamps, particularly earlier generations than the most recent ones, this voltage will cause increases in distortion due to the operating conditions of the input transistors being changed. This distortion can be highly sensitive to the source impedance and the input signal level. In the transresistance mode the virtual ground does not move, removing this source of distortion. Modern audio IC opamps are generally designed with this problem in mind and exhibit negligible changes in distortion when operated in non-inverting mode. These are the two main aspects of current versus voltage mode inputs. There are other, more obscure, aspects. I chose voltage mode, but also chose appropriate opamps to minimize the down side of the choice. The bottom line is, when properly designed both current and voltage input designs can have equivalent performance from the perspective of distortion, frequency response etc.- but the voltage input design is more predictable and easier to specify. The voltage input design produced has very precise gain, extremely precise RIAA compliance and unmeasurably low distortion.
|
The distinction between virtual and actual ground is a subtle one. When an opamp inverting input is used, the virtual ground is extremely similar to a real ground as the action of negative feedback makes it so. The difference is in the error term- i.e. the output voltage divided by the open loop gain of the amplifier, together with any impairments added by the amplification system. This difference can be extraordinarily small, so arguing that the virtual ground is not a real ground is largely facile. As far as the source is concerned there can be essentially negligible difference between a real ground and a virtual ground. Claiming, arbitrarily, that it is prima facie audibly different as far as the source is concerned is not reasonable. To put this in context. The error term is a function of the opamp gain bandwidth product, open loop DC gain, and the internal sources of distortion, both the intrinsic input non linearity and the output stage non linearity. With high gain bandwidth and high open loop DC gain the error voltage is extremely small in the audio band, and with low intrinsic open loop distortion at the signal levels present at the non inverting input when negative feedback is applied the resultant distortion component of the error signal is also extremely small. These facts make the virtual ground , when opamps of sufficient quality are employed, extremely close to an ideal ground, in fact just about as close to an ideal ground as any "real" ground that you can actually construct. |
I don't doubt that it could be affected. Loading the cartridge causes the cantilever to become stiffer (more work is being asked of it and that has to come from somewhere: the cantilever is thus harder to move)- and thus can introduce the possibility that even though the bandwidth of coil is unaffected, the mechanical aspect of the cartridge will be affected by that added stiffness- possibly making it less able to respond to higher frequencies. |
That is not the case in this instance. The measured frequency response of both cases is within 0.1dB within the audio band and the 1:40 has a 2dB low Q resonance at 90kHZ and the 1:8 has a 6dB peak @ 235kHz. To isolate the contribution of the SUT I left the 1:40 unloaded to reflect 187Ω and placed a 200Ω resistor across the primary of the 1:8. I then level matched them and am hard pressed to tell the difference between the two. This gives me confidence in my belief that the load on the cartridge is responsible for the sonic changes that I reported above. dave
|
Atmasphere......The Ah-Ha moment! http://www.atma-sphere.com/en/mp-1.html Is this the company you represent? I apologize that I did not recognize you as a tier one supplier of high quality phono stages. I will study your web page further. Thanks for being involved with Audiogon and sharing your knowledge!! Lou |
Ground.
Transformers transform impedance. Further, to prevent ringing they must be properly loaded at their output, to something called 'critical damping' where a squarewave input to the transformer results in minimal overshoot. If not loaded the transformer can 'ring' with excess harmonics- its making distortion. Your ears will respond to that as sensing it as loudness and yes, it might even hurt if the volume is up a bit. Because transformers transform impedance its not necessary to load the cartridge directly with a low impedance in order to achieve a low impedance- you can do that on the output side of the transformer as well. IOW putting a lower impedance load on the output will reduce the load impedance the cartridge sees. This is because the only isolation a transformer offers is galvanic and DC; it does not offer impedance isolation. This loading issue is one reason I avoid SUTs- you do have to manage their care and feeding. If the SUT is designed for a specific cartridge, the correct load is probably 47K (but will be different if a different cartridge is used). Its really important to keep interconnect cable capacitance to a minimum. But if you simply have enough gain and your phono section has no worries with the RFI that will be generated by the cartridge/cable interaction, then you have no worries- its plug and play. |
I am not suggesting that if the load is a fraction of the cartridge impedance the stage must be a current amplifier.... I am suggest as a whole current amplification stages will typically load a cartridge with less than its internal impedance. A good example of this is the situation I outlined above where I used an 8Ω cartridge through a 1:8 SUT and then directly compared it to a 1:40 with a 2.2Ω resistor across the cartridge directly. The 2.2Ω resistor was chosen so that the output of the SUT in both cases was identical as was the frequency response from 10Hz to 100kHz. (±1dB). In this case even though the cartridge load was 1/4 the internal impedance when using the 1:40, I would still consider it a voltage gain stage. The result of this experiment was interesting. Even thought the gains of both situations were the same, the 4.7kΩ load through the 1:8 sounded a good 2dB louder. When the gain of the 2.2Ω load was bumped 2dB suddenly it was preferred and then going back to the 4.7kΩ 1:8 at the same +2dB level started to hurt my ears. dave |
