Cartridge Loading.....Part II

Ralph, in an ideal current driven phono stage that uses an op amp to sense current, is the coil of the cartridge connected to that virtual ground that you describe? One end of course. If that is the case, where do they connect the other end of the coil? Thanks.

if I am understanding both Ralph and Dave correctly, there is a difference between them in the definition of a current driven phono stage, in that Ralph says it must be an op amp that does the current to voltage conversion, and which can provide a zero ohm virtual ground. Whereas, Dave said that any device with an input impedance much lower than that of the cartridge internal resistance can act as a current driven stage. Is that correct?

My belief is that the nature of current amplification vs. voltage amplification (namely how they load a cartridge with low vs high impedance) has a dramatic effect on the mechanical behavior of the cartridge and may be partially responsible for the differences heard between the two types.

 It also has a lot to do with distortion and RIAA EQ differences. Separating those out might be a bit difficult.

@dover  This needs to be distilled to the most basic level to get a solid foundation that everyone can build upon equally.  It is not about any particular design and more about cartridge loading as a whole.  My belief is that the nature of current amplification vs. voltage amplification (namely how they load a cartridge with low vs high impedance) has a dramatic effect on the mechanical behavior of the cartridge and may be partially responsible for the differences heard between the two types.

I am not suggesting that all current amps are the same but if we can separate them conceptually from their voltage amp brethren then a discussion about how each loads a cartridge can ensue.  

 

dave

Take a 30Ω cartridge and hook it up to an ideal voltage amp and then another one and hook it up to an ideal current amp.  Now take two AC microamp clamps and monitor the current output of each cartridge.  Will the currents be the same for each cartridge?

@intactaudio I doubt it but that depends on the actual impedance that the cartridge is driving in either case.

@atmasphere @intactaudio 

I think it depends on the individual design.

I know from first hand knowledge that the BMC & ESE Nibiru react differently with different cartridges, but on the other hand I have a bespoke current sensing device built by a cartridge manufacturer that is superb across all my cartridges ranging from 3-40ohms internal impedance.

Also I recall the current sensing Goldmund PH2 sounding superb across a variety of cartridges, regardless of internal impedance of the MC.

I haven't kept track of which current driven phono stages on the market use op amps or discrete transistors or tubes in the input I/V stage, although I don't know of any that use a tube or how you could use a tube in that fashion. 

@lewm Transimpedance preamps have to use opamps since that is the only way to get a virtual ground. You can use discreet opamps as those do exist (a friend of mine designed his own) but you do need an opamp to pull it off.

Take a 30Ω cartridge and hook it up to an ideal voltage amp and then another one and hook it up to an ideal current amp.  Now take two AC microamp clamps and monitor the current output of each cartridge.  Will the currents be the same for each cartridge?

@intactaudio I doubt it but that depends on the actual impedance that the cartridge is driving in either case.

Too late to edit my post, but I meant to say, "It connects the cartridge to the emitters of an array of discrete transistors."  Not "It connects the cartridge output to an the emitters of array of discrete transistors."

Sounds like driving a triode via its cathode, but I won't dare go there.

Ralph, I just had a “duh” moment. Sutherland describes the input of his Loco and Little Loco as a “virtual” short circuit. I had heretofore interpreted that word in its more literary sense; virtual meaning “nearly “or “close to”. Thanks to your input, I now see he means it electronically (virtual). I also see that nearly all current drive phono stages do use an op amp input. The BMC MCCI being an exception. It connects the cartridge output to an the emitters of array of discrete transistors.

OK... lets try a different tact since i do not think ground (be it virtual or real) matters in this situation.  I am simply relying on Ohm and Kirchoff for this ideal case.

Take a 30Ω cartridge and hook it up to an ideal voltage amp and then another one and hook it up to an ideal current amp.  Now take two AC microamp clamps and monitor the current output of each cartridge.  Will the currents be the same for each cartridge?

dave

I haven't kept track of which current driven phono stages on the market use op amps or discrete transistors or tubes in the input I/V stage, although I don't know of any that use a tube or how you could use a tube in that fashion.  However, I would guess that many do use a discrete transistor and so by your definition cannot be current amplifiers.  If they all use op amps, then I stand corrected, and right there I have learned something about them.  However, every one that I have investigated was said to have some finite input Z, greater than zero and notwithstanding the cartridge with which it might be matched. (Especially because most of the advertising suggests you can match them with any cartridge having a "low" internal resistance, low being better than higher.)  But I do get that to be a pure current amplifier, the input impedance ought to be zero. Sticking my neck out in saying this, but I would rather gain understanding than worry about negative feedback, no pun intended.

I have been complaining about that on this forum over and over again.  Only be direct questioning can one find out what the input impedance of these "current driven" phono stages actually is, and it's typically from a few ohms in the best case to as high as 20 ohms. 

@lewm I don't know how you could specify the input impedance; it varies with the impedance of the cartridge! Again, the gain of the circuit is defined by the ratio of the feedback resistor vs the input resistor (which is literally the cartridge itself). So if the cartridge is 30 Ohms and the feedback resistor is 300 Ohms, the gain of the circuit would be 10 or 10dB. If the cartridge were only 15 Ohms that would mean the gain of the circuit is 20 (16dB). So the input impedance can only be defined by the fact that a virtual ground is present. But you have another problem, which is that with almost any opamp made you run out of Gain Bandwidth Product over about 20dB of gain or thereabouts.

This means that with cartridges that have a very low impedance the circuit may lose neutrality. Personally I would prefer to have the gain be a set thing so that the cartridge would not be able to affect the phono section in that manner.

Ralph, you wrote, "The '0 Ohms' value you see in so many phono sections that have transimpedance inputs probably isn't helping people to understand what is going on. That value is probably the marketing department talking since they probably didn't understand what a virtual ground is."

I have been complaining about that on this forum over and over again.  Only be direct questioning can one find out what the input impedance of these "current driven" phono stages actually is, and it's typically from a few ohms in the best case to as high as 20 ohms.  Even the term "transimpedance" is a marketing ploy.  Almost as bad as "quantum" used to describe an interconnect or a fuse.

Your other responses are helpful but raise other questions in my mind that I will hold in reserve for now. Thanks for your patience.

(1) what if the input device is a discrete transistor or a tube, not an op amp?

@lewm 

Then there won’t be a virtual ground. So right away its a voltage amplifier not a current amplifier.

(2) the only way I can imagine two points separated by 5 ohms but at the same potential is if and when there is no current flowing. How does that work in this case?

Opamps have nearly infinite gain when open loop; the feedback resistor and the input resistor thus define the gain of the circuit and the virtual ground is formed at the intersection of the input resistor and the feedback resistor (see my prior posts for more information).

There is no connection between actual ground and virtual ground; the latter is created as a result of the feedback meeting the input signal. So there isn’t (as in the case of 5 Ohms) 5 Ohms between the ground and the virtual ground. In fact the actual impedance is much higher.

The ’0 Ohms’ value you see in so many phono sections that have transimpedance inputs probably isn’t helping people to understand what is going on. That value is probably the marketing department talking since they probably didn’t understand what a virtual ground is.

The tricky bit is that in a transimpedance input, the cartridge itself is the input resistor. This means that the actual impedance load on the cartridge varies with the impedance of the cartridge itself- and with it, the gain of the circuit. As I pointed out earlier, the lower the impedance of the cartridge the higher the gain of the circuit.

 

Ralph, two questions:

(1) what if the input device is a discrete transistor or a tube, not an op amp? 
(2) the only way I can imagine two points separated by 5 ohms but at the same potential is if and when there is no current flowing. How does that work in this case?

Thx

Why not?  Consider the case to be an ideal current amp with the appropriate series resistance added so the input impedance is 5Ω.   In this gedanken world the ideal voltage amp and the ideal current amp sound identical.

It seems to me that you are still conflating virtual ground and actual ground as the same thing! As I said before this leads to confusion.

So the 'Why not?' is the same as before: Because that 5 Ohms is a virtual 5 Ohms instead of a real 5 Ohms. The cartridge is not loaded at an actual 5 Ohms. 'Virtual Ground', again, is opamp parlance for a point in the circuit that exists at the same potential as ground but isn't actually ground.

I recommend that you read up on opamp operation since this seems to be the hanging point. Here's a short tutorial opamp virtual ground.

If you don't want to do that, just keep in mind that 'virtual ground' isn't the same as actual ground. So the cartridge would not be loaded at an actual 5 Ohms even though the virtual ground is 5 Ohms.

The question cannot be answered at all if current amplification is used.

Why not?  Consider the case to be an ideal current amp with the appropriate series resistance added so the input impedance is 5Ω.   In this gedanken world the ideal voltage amp and the ideal current amp sound identical.

If we can agree on this then we can get to the question I am really curious about and that is....  How much of the sound of current amps vs. voltage amps is simply due to the radically different load the cartridge sees? 

 

A simple experiment I have been contemplating playing with is to compare the loading extremes is to use a 1:10 sut loaded with 300kΩ to load an 8Ω cartridge with  3K.   Then take the same cartridge and feed a 1:20 and apply an 8Ω resistor as a load directly to the cartridge.  The extra 6dB of gain from the increased turns ratio will be offset by the ~6dB loss of the cartridge being loaded with its internal impedance.  One could even take it a step further and try a 1:40 with a 4Ω parallel load to see the sonic effects of the extremes.  

dave

 

The first question that needs to be addressed is in a perfect world with ideal amplification, will a 40Ω cartridge sound the same into a 5Ω load as a 47kΩ load? 

Right up to this point I was in agreement with the prior text of this post. With this question we can safely say the answer is 'No.', assuming that the perfect amplification is voltage amplification. The question cannot be answered at all if current amplification is used.

If that is a static load (IOW, a resistor) then the cartridge will be making 4 orders of magnitude more work! That work has to come from somewhere, otherwise a new branch of physics is created 😉

So it will certainly cause the cantilever to be harder to move (stiffer) and that will affect how the cartridge 'sounds'. It won't affect the bandwidth of the coil in the cartridge at all- but will have an enormous affect on the mechanical aspect as the coil will have become a significant load with 5 Ohms loading it in turn. Also, the output level will be considerably decreased!

The topic of this thread is cartridge loading and it only makes sense to look at it from the two terminal perspective of the cartridge without concern of the "technology" used to provide that load.   There are two basic extremes of operation of a cartridge.  It can operate as a current generator where the load value is << the cartridge internal impedance or it can operate as a voltage generator where the load value is >> than the cartridge internal impedance.  There is also a fairly grey area inbetween these two extremes where the load value is ≈ the cartridge impedance.  For this basic discussion I think the two extremes need to conceptually be looked at from the ideal with respect to how the cartridge converts a mechanical movement into an electrical signal.  Since it is the source to load relationship that dictates whether a cartridge generates current or voltage it becomes important to determine if changing the load causes any mechanical or electrical change to the behavior of a cartridge.  

 

When operating as a voltage generator the load can easily be modified over a fairly wide range and still maintain the basic principles of operation.  I think most will agree that loads  of 10X the cartridge impedance and up have a cartridge operating squarely in the voltage realm and people will start to cry foul as your load approaches  the cartridge internal Z.  This doesn't have anything to do with actual cartridge behavior and everything to do with the type of amplification that follows.  For voltage amplification the unique case where Rsource=Rload nets a 6dB voltage loss and in the case of microvolt level signals that is huge.  Going to the case where Rload is 1/4 that of Rsource the voltage loss will be 18dB which immediately disqualifies that as an option for many.  The problem with that categoric disqualification is that you are trying to make a cartridge operate as a source of current into a voltage amplifier. The problem has nothing to do with the actual load and everything to do with using the wrong tool for the job.  If the goal is to actually load the cartridge with 1/4 the internal impedance then that load should simply be provided by a current amplifier.  If we want to discuss the effects of loading on the behavior of the cartridge we have to assume that the appropriate type of amplification is used.

The first question that needs to be addressed is in a perfect world with ideal amplification, will a 40Ω cartridge sound the same into a 5Ω load as a 47kΩ load? 

 

On the subject of phono input impedance as it relates to the discussion between Atma-sphere and Intact Audio, one should also keep in mind that every "current drive" phono stage seems to be a bit different from every other "current drive" phono stage, at least on the subject of input impedance.  Most advertised "current drive" phono stages do have a finite input impedance greater than zero, whether that is virtual zero or whatever.  A couple of years ago, I looked at 4-5 different products and the range of measurable input Z was from a few ohms up to as much as 20 ohms.  A unit with a real 2-ohm input Z will probably react differently to a LOMC with an internal resistance of from 2 to 10 ohms than a unit with a 20-ohm input Z, current, voltage or whatever.  The water gets really muddy.  They want to dumb it down for us consumers.

Dear friends: Looking to almost all my vintage LP test recordings I found out that I have some even sealed as one from Micro-Acoustics and the Ortofon serial 003 that yesterday opened and listen to it.

It's not a test tones and the like but the lovely tracks are MUSIC, this LP is an Ortofon collaboration with the label Opus 3 that in the past ( too ) made 3-4 test LPs.

Well, first than all this Ortofon LP is really good centered with no waves you can detect and even that's a vintage recording not only is a great recording but the LP recorded surface is dead silent, even the band that separates the tracks is dead silent.

 

If you can find out buy it, it's a good investment for you and your room/system set up.

 

R.

Dear friends: Looking to the PM charts that @intactaudio shared with us yesterday I took in count that ( for my self. ) I can measure it too due ( as I posted several times in this forum. ) that I own around 20+ different vintage comercial test LPs from: CBS, Shure, JVC, Stereo Review, HiFI, Vanguard, B&K, Ortofon, Audio Technica, etc. etc.

 

Through them I have 4 tracks IMD dedicated and rigth now I'm talking with some of my audio friends looking for the ritgh phono stage that permits in easy way changes in the cartridge loading because in my unit I can do it unsoldering/soldering resistors . As I said I will do for my self satisfaction and with withness of the gentleman that will share his phono stage for 3-4 hours any day in the afternoon.

 

So " stupid " I'm that having a solution I did not see way before.

 

R.

The two statements you quoted from me seem to align well with each other and I was unaware that there was a different versions of ohms law for static vs dynamic loads

At any rate, Moncreif threw off his numbers by using a 5 Ohm load

I agree it is an interesting choice but his measured results clearly show signal and if if anything a lower noise floor so I fail to see where the issue is or how it invalidates his results.

In the case of a transimpedance input, feedback is applied to the output of the cartridge. Its a fair amount of feedback too- the more output the cartridge has the more feedback. That is quite a bit different than a simple resistor- you can’t equate a virtual ground with a static resistance- for one thing, you need an opamp to even create a virtual ground.

Ohm’s Law certainly is in play (how could it not be), but the issue here is that while a cartridge has its output at a virtual ground, that is significantly different from having the cartridge drive 0 Ohms (IOW, if it were actually tied to ground). In the case of the former, the actual input impedance is dynamic and isn’t actually 0 Ohms, so amplification can occur because a signal is present. In the case of the latter, the load is actually a short and because the signal is shorted out, no amplification can occur.

’Virtual’ means ’almost or nearly as described, but not completely or according to strict definition.’ If the 0 Ohms of a virtual ground is conflated with the 0 Ohms of actual ground, confusion is the direct result.

I say Peter threw off his numbers because he chose a value that no-one would ever use (and a static value at that, no opamp involved, so the load was causing the output of the cartridge to change in a significant way, whereas real-world loads have negligible effect) since its a reasonable expectation that if you are going to use a load on a cartridge, you’d likely start with one that is 10X the source impedance of the cartridge.

I can see using static values lower than that, but not one that’s actually lower than the the source impedance! Barring a good explanation for that, when I read that in his article I found I simply had to take his results in abeyance. I’d have to read the article again (Google defeated my attempts to locate it just now), but IIRC he had some variables left uncontrolled that I felt at the time might affect his results.

One way around this is to ignore that transimpedance inputs exist and simply focus on what happens to the output of any source when the load is a fraction of that of the source. That’s really what I’m getting at here, if Peter was actually suggesting that we use such loads both back then and now the extra gain needed would be impractical.

Ralph,

The two statements you quoted from me seem to align well with each other and I was unaware that there was a different versions of ohms law for static vs dynamic loads

At any rate, Moncreif threw off his numbers by using a 5 Ohm load

I agree it is an interesting choice but his measured results clearly show signal and if  if anything a lower noise floor so I fail to see where the issue is or how it invalidates his results.

dave

 

Now, now... let's try and keep it civil.  I've enjoyed the discussion this far and am impressed by many members knowledge base.  Which is very helpful to the lion's share of members!

That laST POST IS PART OF THE WHOLE REGARDS STUPIDITY COMING FROM THE SAME PERSON, COMING FOR HIS FRUSTRATION .

@intactaudio  audio " falls " in that person game ( because intactaudio in good faith gentleman unknow that person game. ) that when he can't win then he follows been argumentative and goes " around and around "  with different issues than the one under discussion ( exactly like here. ) makind a way deviation from the main subject.

I followed his " game " when he already bbeated and I did it for many years till I learned.

That's why JC just does not  follows that stupid game and never suported him with the IMD issue discussed for years.

Please look to what stupid levels goes his stupidity:

""" At any rate, Moncreif threw off his numbers by using a 5 Ohm load, since that is not only not a........., if he really wanted to make his point valid he needed to show the results using real world loads that are actually in use. "

Certainly it's not PM who should do that  because PM shows at 100 ohms too but more important : that stupid man not only does not shows nothing/measures to prove his point but now he ask that the gentleman that measured and proved that the IMD is developed by the cartridge loading effect still makes more measures: GO FIGURE ! ! !

 

Yes, in our world exist any kind of stupidity we could think.

 

R.

 

I didn’t mention a dead short and was only referring to the two terminal impedance the coil of a cartridge sees. Any reference to ground be it real or virtual does not factor into the load seen by the coils. Surely there has to be an actual input impedance for a current amp and it has to be low otherwise the coils will not generate any current to amplify.

Do you see how this above does not jive with this:

that depends on what load the input of the following stage gives.

If it is a voltage amplifier with 47kΩ, a 30Ω cartridge loaded by 5Ω it will be 17dB down.  When you replace that 30Ω cart with a 2Ω cart the output will only be down 3dB. If it is a current amplifier with a 1Ω input impedance a 5Ω parallel load will lower the current into the 1Ω input node by1.6dB with both the 2Ω and the 30Ω cartridge. The absolute currents will be different for the 2Ω and 30Ω carts but the relationship of how the 5Ω load affects a 1Ω input impedance stays the same.

Transimpedance phono sections have a dynamic load whereas a resistor is a static load. This is because the so-called 'virtual ground' (which will be 0 Ohms) occurs where the feedback resistor of an opamp meets the input resistance, which in this case will the cartridge itself.

At any rate, Moncreif threw off his numbers by using a 5 Ohm load, since that is not only not a real-world value that no-one would ever use, but is also one that would significantly decrease the output of any LOMC cartridge to the point that its output would be unusable (which is why its not real world...). Keep in mind that transimpedance phono sections didn't exist back then. As I mentioned previously, if he really wanted to make his point valid he needed to show the results using real world loads that are actually in use.

I didn’t mention a dead short and was only referring to the two terminal impedance the coil of a cartridge sees. Any reference to ground be it real or virtual does not factor into the load seen by the coils. Surely there has to be an actual input impedance for a current amp and it has to be low otherwise the coils will not generate any current to amplify. I am not trying to get into an in depth analysis of how various transimpedance amplifiers work but address the general first order behavior of the system and believe that a cartridge operating into a ideal voltage amp behaves differently than the same cartridge into an ideal current amplifier primarily due to the fact that the loads are at opposite ends of the spectrum.

Try placing a 5 Ohm resistor across the output of any LOMC cartridge and see what happens 😁

that depends on what load the input of the following stage gives.

If it is a voltage amplifier with 47kΩ, a 30Ω cartridge loaded by 5Ω it will be 17dB down.  When you replace that 30Ω cart with a 2Ω cart the output will only be down 3dB. If it is a current amplifier with a 1Ω input impedance a 5Ω parallel load will lower the current into the 1Ω input node by1.6dB with both the 2Ω and the 30Ω cartridge. The absolute currents will be different for the 2Ω and 30Ω carts but the relationship of how the 5Ω load affects a 1Ω input impedance stays the same.

dave

When you consider the proliferation of "current mode" phono inputs in vogue the 5Ω value isn't so strange.

Transimpedance phono sections have the cartridge driving the 'virtual ground' of an opamp circuit. That's quite a bit different from driving an actual short (0 Ohms)! For example, if the cartridge isn't present, the virtual ground does not exist. They really aren't an example in this context.

Try placing a 5 Ohm resistor across the output of any LOMC cartridge and see what happens 😁

 

Dear @intactaudio  : " 

and 100Ω values are odd but that is secondary to demonstrating the effect. "

 

and something important is that PM is the only gentleman that showed/measured  in that regards,

The critic made by atmasphere is useless and for any one is easy to post that kind negative  comments. Could be better to prove with measures that PM is wrong, this is the way to do it but obviously till that happens PM it's  not wrong and in this regards a congratulations to him is the least we can do for.

Again, thank's for your PM information that trully and finally puts the " ligth " we all need it about.

 

R.

 

 

 

I don't usually get too caught up in the Interface methodz being discussed in the descriptions offered.

Using the Manufacturers recommendations, has been quite successful for my own purposes.

I have a selection of Cables, as well as few SUT's and cam also have the use of Head Amp's

I will swap different configurations to see what develops in the SQ. 

I also have a Phon' with a methon to control input capacitance, input impedance and adjust gain. 

I will use this to learn if a chosen configuration is able to be improved upon. 

I do not think the value of the loads chosen invalidates the test.  Sure it may over-exaggerate things in the traditional sense in the voltage realm. When you consider the proliferation of "current mode" phono inputs in vogue the 5Ω value isn't so strange.

dave

I would say no since the two loadings  PM shows for his IMD are 5Ω and 100Ω both of which will surely damp any possible LC resonance which would then eliminate the whole RFI aspect. 

@intactaudio FWIW 5 Ohms as a load is so low that most cartridges will produce measurably less output whereas at 100 Ohms the output would hardly be affected. At least this is true of any LOMC cartridge I've measured (a cartridge of 30 Ohms would be affected by both). Knowing that, when I saw the 5 Ohm value in Moncreif's measurements I was forced to take his conclusions with a grain of salt. I think he would have produced better science with 75 Ohms as his lower limit.

Dear friends @intactaudio  : I made an extensive search looking for documented/measured information about the JC comment on IMD and looking for too if JC mentioned a second time that issue and he never did it, at least I can't find out.

Btw, here information from experts, first by @hagtech :

 

"" As mentioned earlier, the peaking is best damped by lowering the load resistance. This is why MC cartridge manufacturers often request loading of about 100 ohms. The next plot shows the 5mH 10 ohm cartridge loaded with 200pF and a variable resistance. ..................... Most MC cartridges have less inductance than this example (chosen to highlight the issue), and so the typical loading value of 100 ohms is usually quite reasonable. "

 

Next comes by the designer/manufacturer of SUTs as intactaudio:

 

" Most modern moving coil cartridges have a source impedance of about 10 ohms and the “load impedance ten times the source impedance” rule suggests 100 ohms is a good choice for load impedance ...... This is well in line with the recommendations from many cartridge manufacturers. Anything above 100 ohms should be equally suitable.
Does the cartridge's tonal balance change with load impedance? It certainly does if the cartridge is a moving magnet type, but low output moving coil cartridges are much less sensitive to changes in the load impedance. Users sometimes claim that higher load impedances produce a brighter sound than lower ones, but cartridge manufacturers tend be non-specific about recommended load impedances, often recommending a wide range or simply anything above a minimum impedance.
The recommendation of Rothwell Audio Products is in line with Ortofon, Audio Technica and most other cartridge manufacturers - that 100 ohms is a good value for most cartridges, and that the exact value is not critical as long as it is well above the cartridge's source impedance.
One thing is certain, and that is that the load impedance should not be equal to the cartridge's source impedance. That would produce a 6dB loss of signal (when there's often only a few hundred microvolts to start with) and seriously compromise the signal-to-noise ratio.  "

 

R.

Dear @intactaudio  : Re-reading several posts here and in other forum about the loading issue I tend to agree with you. Please let me explain:

first JC works graphs here were not to prove nothing about IMD or frequency changes because MC loading.

That's why he posted that " FR changes is bogus " when he posted this to a forum member who asked about the FR effects of cartridge loading: brigth vs dark sound. Doing his thread answer ( JC ) made a comment about IMD but was only a comment to re-afirm/confirm that exist no FR changes because loading. A time comment and nothing more than that.

PM confirmed no FR chnages with cartridge loading and all these is the only true  about cartridge loading and FR.

The JC advise is the lower cable capacitance the better.

@larryi pointed out:

" One position is that low loading is preferred because it CAUSES distortion that is perceived as high frequency information and people have grown accustomed to, and prefer, the distortion. "

 

According what you said PM posted:

" finally proposes that the excess IMD caused by a lightly loaded MC cart is often perceived as high frequency detail that many have grown accustomed to and the "dark" sound of heavily loaded cartridge can be due to a system being tuned for the typical lightly loaded case. "

 

@hagtech  posted with no other significant comment:

" 

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 "

 

 

All those post coincide in that specific regards.

 

Now, I can remember that over 30 years now I almost always recomended to load highly the MC cartridges at around 100 ohms and doing what larry posted: move the volumen position to recover the SPL and with this simple " even SPL " the dark sound just gones and the sound will shines with lower distortion levels that at 20k-47k.

 

Today with your help of those PM works and the other gentlemans help I confirm that over the years my take about those 100 ohms loading is just rigth and as a fact that's the load impedance that I used and use with dozens of LOMC cartridges that I owned and own in my active high gain phonolinepreamp and when I'm using a SUT in my unit I set up the MM load at 100k. Everything works excellent.

 

Thank's to you all to share a critical information for me. Good !

R.

 

R.

 

 

 

 

 

So, if PM did not shows from where comes the IMD only JC is rigth?

I would say no since the two loadings  PM shows for his IMD are 5Ω and 100Ω both of which will surely damp any possible LC resonance which would then eliminate the whole RFI aspect.   I will note that the cartridge used has a 30Ω internal impedance so the 5Ω and 100Ω values are odd but that is secondary to demonstrating the effect.

 

Dear @intactaudio  : This is part of the J,Carr w.papers ( I never seen any from atmasphere. ) that I'm sure you are aware of it:

• Kleos electrical model (9uH, 5.4ohm, 8pF)
• Lyra Phono Pipe Very Low Capacitance tonearm-to-phonostage cable 120cm actual measurements (0.75uH, 0.325ohm, 32pF)

What these tell me (among other things) is that, all else being equal, changing just the interconnecting cable (each of which has a different capacitance characteristic), changes the optimal resistive load; and if you can afford to bring up that peak in the MHz to something <10dB then you can bring up resistive loading to about 500-1K ohms even with a highly-capacitive cable; and finally, you are not really affecting the audible high frequencies with any resistive load shown. "

 

Yes he said too that a phono stage could be overloaded by the inductance, load impedance and cable capacitance if the designer does not took in count this issue and when that happens appears as IMD. Today SS designs comes with really high overload/headroom margin/level.

You said:

" Moncrief suggests (and shows) that for MC carts, IMD distortion levels are directly related to applied cartridge load. "

but atmasphere that has that IAR 5 posted:

" did not show is where the IMD was coming from..."

So, if PM did not shows from where comes the IMD only JC is rigth?

Because exist a big difference in both assertions what you said that PM showed means that always appears the IMD when what JC said is that the IMD sometimes could appears when the phono unit design was not designed tooking in count that " issue ". 

I think that you need re-read the PM w.papers or pasted here for all we can learn and most important to answer my question to you.

 

R.

 

 

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

I need to clarify: It has no effect on the output of the coil. 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.

did you ever get a chance to look at the copy of IAR #5 I sent you?  I find it entirely plausible that making the cantilever easier / harder to move would have a sonic impact on the sound of a cartridge. 

I did- thanks- and agree, since this likely has an effect on how it tracks. IMO what Moncrief did not show is where the IMD was coming from; IMO it is caused by the phono section rather than the cartridge directly.

What it boils down to is that loading matters to the sound, but there is some disagreement here as to why it matters and the cause of the sonic difference.  One position is that low loading is preferred because it CAUSES distortion that is perceived as high frequency information and people have grown accustomed to, and prefer, the distortion.  Another point made here is that RFI overloads some electronics causing distortion which is ameliorated by loading that damps RFI.  I suppose these are not contradictory statements and they may both account for some preferring low loading and others preferring more loading.  Jonathan Carr (Lyra cartridge designer/builder) says that low lading is preferable, because it preserves the high frequency response, which is one of the things people pay big bucks to get from MC cartridges, but, that higher loading might be necessary to kill RFI that can overload some gear (Atmasphere's position, and I tend to agree). 

As to Atmasphere's response to my statements about the sonic effects of loading-- that loading has no effect on the cartridge, except to make the cantilever harder to move-- I was merely stating that the effects of loading changes can be heard, not that loading physically affects the cartridge.  There are cartridge experts that say that the back EMF changes from loading are so negligible that the effect on movement of the cantilever is mostly theoretical an not a practical reality.  

Perhaps my statement about having to compensate for difference in loudness where a low value resistor is used (high loading) was misconstrued.  I was merely pointing out that when making a comparison, to be fair, one might have to increase the volume a bit for the high load scenario to compensate for the voltage drop across the load resistor; with a high value resistor (low load), that drop is less significant  

@rauliruegas

What Jcarr and in parallel Ralph are saying is completely different than what is presented by moncrief.  They all agree that loading has no effect on the measured frequency response of a cartridge but any similarities end there.  Ralph and Jcarr suggest the unloaded "harshness" is caused by the MC cartridge inductance resonating with cable/input capacitance resulting in input overload of a phono stage that is not "RFI stable".  Moncrief suggests (and shows) that for MC carts, IMD distortion levels are directly related to applied cartridge load.

dave

Ralph

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

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

did you ever get a chance to look at the copy of IAR #5 I sent you?  I find it entirely plausible that making the cantilever easier / harder to move would have a sonic impact on the sound of a cartridge.  Add to this that this effect will be dynamic based on the musical content and things get interesting.  If you trust the measurements made by Moncrief, he clearly shows a reduction of IMD and it isn't a huge leap of faith to believe that the degree of measured IMD change he shows would have an audible result.

 

dave

Sort of makes a good argument for transimpedance as the initial stage of a phono preamp . . .

The lower value 200 ohm vs. 47k ohms means more loading which tends to attenuate higher frequencies (because we hear things in terms of overall balance, attenuating highs can also  be perceived as more bass).

If light loading is entirely added intermodulated distortion and the "real" and "accurate" sound is what you get with high loading, I will take distortion. 

The loading has no effect on the cartridge other than making the cantilever harder to move. You can take any LOMC cartridge and put it on the bench. Using a squarewave generator (at a very low loutput, so as to not damage the cartridge), you can put the cartridge in series with the squarewave and then measure the output. With no resistor in parallel this is an unloaded inductor. What you will see on the oscilloscope is a nice squarewave, looking really quite a lot like the input, neither attenuated or rounded and with no overshoot! This is simply because the inductance of the coil is too tiny to ring at audio frequencies.

So the 'brightness' we often hear is coming from somewhere else!

Putting a resistor in parallel will not affect that. So the resistor is not affecting the bandwidth of the cartridge. But it is interacting directly with the electrical resonance, which is a product of the inductance of the cartridge and the capacitance of the tonearm cable.

As we can see from the page http://www.hagtech.com/loading.html

the peak can be substantial. The reason is something called 'Quality' or simply 'Q'. Inductive coils can be long and narrow, having a low Q value, or short and wide, having a much higher Q value. The higher the Q value the higher the peak and the narrower the band of frequencies it covers. LOMC cartridge have high Q coils in them for lowest mass.

Some preamps don't like having all that RF noise caused by the peak at their input. So they do weird things and one of them is distortion. Loading knocks out the electrical resonance and if the preamp has a problem with the RFI, the brightness along with it.

One would have to compensate for the loss of gain from using such a resistor, but, one will hear quite a difference in sound

This statement is only true if the preamp is sensitive to the RFI at its input. If not, no difference will be heard. Most designers simply don't take the implications of this electrical resonance into account in their phono designs, which is why this loading conversation persists.

 

Dear @intactaudio  : You are rigth and what PM IAR 5 posted was confirmed by J.Carr when in other thread on the same issue posted:

 

" To claim that the loading affects the measurable frequency response of the cartridge is bogus. However, if inappropriate loading bathes the phono stage in copius amounts of high-frequency noise, it may start to distort (unless the designer implemented various techniques to make sure that this won't happen), and the result will likely be intermodulation distortion.  "

Regards and enjoy the MUSIC NOT DISTORTIONS,

R.

I suppose I should have preceded my comments with the phrase "I perceive as" because I did not take measurements.  In any case, the sound changes, both with loading changes and VTA, and whether or not it is actually added distortion that one might be favoring with a higher VTA and lower loading (higher resistance in parallel), I don't really care; I like what I like.  I suspect that a lot of the appeal of vinyl playback IS something added, and perhaps something lost, as compared to the original recorded signal, but, I don't have any sort of religious commitment to authenticity/accuracy.  I happen to like, for example, many works of visual arts that don't depict their subjects with the same "accuracy" as high definition photography.  

If light loading is entirely added intermodulated distortion and the "real" and "accurate" sound is what you get with high loading, I will take distortion.  As an experiment, one could try the loading of a MC with relatively high source impedance (like a Denon 103) with something like a 10 ohm resistor.  One would have to compensate for the loss of gain from using such a resistor, but, one will hear quite a difference in sound as compared to a light loading (e.g. 47k); I would not chide anyone for preferring lightly loaded and accuse them of having incorrectly becoming "accustomed " to light loading.  

The lower value 200 ohm vs. 47k ohms means more loading which tends to attenuate higher frequencies.

If this were the case it would be easily measured yet I have yet to see this actually documented.  

Another way to attenuate highs is to lower the VTA/SRA

This is another case of something widely accepted, easily measured yet completely undocumented.

I want to be clear that I am not doubting there is a change in sound from varying load or changing SRA, I am just suspect about the "change in frequency response" explanation that is widely accepted as the cause. 

Peter Moncrief in IAR 5 makes a compelling case with measured confirmation that loading of an MC cartridge does not materially effect the measured frequency response of a MC cartridge.  He then goes on to show how loading does measurably change the amount of IMD created from the trackability tones on the Shure TTR103.  He then finally proposes that the excess IMD caused by a lightly loaded MC cart is often perceived as high frequency detail that many have grown accustomed to and the "dark" sound of heavily loaded cartridge can be due to a system being tuned for the typical lightly loaded case.

dave

 

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

 

This is a common trick for many listeners over 60.  Brings back the "airiness" of youth.  Do whatever sounds best for you, not others.

@larryi to add what he said, it is one of the best things about vinyl. On one hand you want some setup to be dead on, cart alignment etc. But, when it comes to final sound there are lots of possibilities between loading, VTA, and VTF (to a degree). All can be tweaked to achieve just about any realm of balance desired. 

The lower value 200 ohm vs. 47k ohms means more loading which tends to attenuate higher frequencies (because we hear things in terms of overall balance, attenuating highs can also  be perceived as more bass).  Another way to attenuate highs is to lower the VTA/SRA (lower the pivot point of the tonearm).  This means that, to some extent you can play around with both loading changes and small VTA/SRA changes to find the best combination for achieving the tonal balance that you want.  I know this adds to the complications, but, it also may enhance your sweet spot.  

Yep, your correct!

Thanks to all for the support!

Well, played many favorite records at 47k for awhile.  Didn't like it overall.  A little to bright, if that's a good analogy. 

@quincy It is. If you experience brightness, IME this is because the phono section really isn't happy with RFI at its input. So loading is really the best thing you can do.

Well, played many favorite records at 47k for awhile.  Didn't like it overall.  A little to bright, if that's a good analogy.  Switched loading to 200 ohms yesterday.  Better.  Not much difference from the original 500 ohms I've been running for the last decade.   Will leave it at 200 and call it good!