Cartridge impedance loading question

I'd start with the 100 ohm setting, but the settings are
pretty easy to switch. Try them all and see what sounds
better.

Pretty easy to switch for SOME of us. I have to open the unit and remove and replace resistors... Don't tell me I only have to do it once when setting up the cartridge...I've already done it once, but wonder if a different value might be better.... The joy...

Stringreen...the OP's Lehmann has dip switches inside. He could put the cover back on, but leave the screws off until he found the right setting.

I think even you could handle that? :-)

The correct loading for the cartridge is 47K.

However, this may result in radio frequency bursts that might disturb the preamp. That is why it is equipped with loading options. The RFI (Radio Frequency Interference) is caused by the excitation of the RF circuit formed by the cartridge inductance and the capacitance of the interconnect cable. The loading detunes the circuit so the RF bursts cannot occur.

Generally speaking, the higher the load impedance the better, while at the same time being sufficient to detune the RF circuit such that no interference is heard (which will manifest as a brightness).

Another way to put this is that if tonality is unchanged, go with the highest impedance you can. This will allow more output from the cartridge.

I owned that excellent cartridge and loaded it at 100 Ohms.

The correct loading for the cartridge is 47K ?

There is no "correct" loading. Assuming you're going straight in, why don't you start at 100 ohms as suggested by Shelter and adjust it to taste?
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1077125197&openfrom&1&4#1

I've used this cartridge for a number of years.
My various phono stages have all been of the moving magnet kind, 47Kohms at input. I have adjusted loading by means of different step up transformers.

For a long time I used an sut that reflected a load of 470 ohms back to the shelter, while stepping up its output voltage by 10 times. (aka 1:10 turns ratio)

And I enjoyed the cartridge quite a lot at this loading.

I have also loaded this cartridge at 209 ohms by using a sut with a turns ratio of 1:15.

With regard to your options with the Black Cube I'd try it at both 100 ohms and then 470 ohms. Choose between those.

I haven't tried it, but it has been suggested to me by someone who has that a 1000 ohm setting works very good with the 501-II. For me that would require an SUT with a 1:5 turns ratio.

My phono stages that I have used with the Shelter have been tubed, except for a couple that I tried for brief periods and returned. I haven't tried the Black Cube.
Current stage is a Hagerman Trumpet which I find quite ageeable with the rest of my signal chain.

And, of course, your mileage might (and probably will) vary.

-Steve

-Steve

There is no "correct" loading. Assuming you're going straight in, why don't you start at 100 ohms as suggested by Shelter and adjust it to taste?

I take it from this an other comments that my post was not read through completely! So, to reiterate in other words:

The correct loading for any cartridge will be such that it does not ring at audio frequencies- IOW if you run a squarewave through it, a squarewave will come out with no ringing.

With any LOMC cartridge ever made, this will be the case at 47K. So why do we hear differences? It has not so much to do with the cartridge and **everything** to do with the phono preamp. If the preamp is sensitive to Radio Frequency Interference, then loading the cartridge will affect tonality as it detunes the RF circuit formed thus:

The RFI (Radio Frequency Interference) is caused by the excitation of the RF circuit formed by the cartridge inductance and the capacitance of the interconnect cable. The loading detunes the circuit so the RF bursts cannot occur.

-as I mentioned earlier. IOW, if loading is audible in your system, your phono section is sensitive to RFI.

Please note that the correct loading value for such a preamp cannot be predetermined since the cable is part of the RF circuit and its capacitance will affect the value. If the manufacturer of the cartridge recommends a particular value, it simply means that *their* reference preamp has troubles with RF and nothing more. But you will find that most manufacturers recommend 47K as it is correct.

* The correct loading for any cartridge will be such that it does not ring at audio frequencies- IOW if you run a squarewave through it, a squarewave will come out with no ringing.*

Ringing at audio frequencies might be a your criteria for loading an MP-1, but there are certainly other considerations for the rest of us, and I would think for MP-1 users as well. That is the sound, irrespective of RFI.

That bit about squarewaves is cute, but would leave a lot of people scratching their chin and changing load. I'm not saying your criteria is irrelevant, but it's not the ONLY criteria.

* With any LOMC cartridge ever made, this will be the case at 47K. So why do we hear differences? It has not so much to do with the cartridge and **everything** to do with the phono preamp. If the preamp is sensitive to Radio Frequency Interference, then loading the cartridge will affect tonality as it detunes the RF circuit formed thus*

Changing load does not necessarily affect tonality. The highest value or 47K is often not the most desirable. BTW, why stop at 47K, why not 1M or infinite?

The answer has to do with how the phono stage reacts to RFI as I have pointed out.

Designers also have to be pragmatic about what sort of input impedance is needed to control noise! If it were to be high as you ask about, controlling noise becomes a major problem in a high gain circuit! So 47K was derived as a reasonable compromise decades ago- it allows low noise and a moderate, easy load for almost any phono cartridge.

Ringing at audio frequencies might be a your criteria for loading an MP-1, but there are certainly other considerations for the rest of us, and I would think for MP-1 users as well. That is the sound, irrespective of RFI.

To be clear, 'Ringing at audio frequencies' is no more a consideration for our preamp as any other, as such only occurs with high output moving magnet cartridges. For them, the inductance is much higher and so loading is important.

Regarding the sound, it cannot be considered 'irrespective of RFI': in plain and simple terms if the circuit has RFI problems **the sound will not be right if RFI is present!!** If such is the case then loading will have a beneficial effect.

In more detail: if the circuit is sensitive to RFI, due to poor layout, lack of input stopping resistors, RFI filters, bad grounding (IOW anything that can cause RFI sensitivity), etc., the result will be that RFI will adversely affect the sound. The RFI is generated by the pickup and cable itself: it is not a matter of shielding from radio stations.

Until this fact is understood loading will remain mysterious and a matter of debate.

Ringing and squarewaves is not just cute, it is part of the toolkit one uses to do circuit analysis. It might interest you to know that many years ago I tried to make a box that one could simply plug in the phono cables from the arm and the box would sort out what the right loading was. It was during experimentation to gather data that I saw that LOMC cartridges don't ring at any frequency anywhere near the audio range- in fact even with a 100KHz squarewave to 'ring' them, they still just pass the squarewave perfectly. Once I understood this fact, I was then able to make changes to our preamp design to make it more RFI resistant at its input, which had the effect of making the low impedance loading resistors nearly irrelevant and also improved the sound at the same time- that latter bit of course is what we are all after.

So loading is not about LOMC cartridges and it is entirely and 100% about good circuit design in the phono preamp.

*The answer has to do with how the phono stage reacts to RFI as I have pointed out.*

Loading encompasses more than RFI as I have pointed out.

*Designers also have to be pragmatic about what sort of input impedance is needed to control noise! If it were to be high as you ask about, controlling noise becomes a major problem in a high gain circuit! So 47K was derived as a reasonable compromise decades ago- it allows low noise and a moderate, easy load for almost any phono cartridge.*

1M doesn't seem to be much of a problem with Herron phono stage, but that's beside the point. 47K became a default standard for HO carts, not LO carts. For 4-ch it was 100K, but that's low gain. Look at vintage preamps and see what the loading options are.

*Regarding the sound, it cannot be considered 'irrespective of RFI': in plain and simple terms if the circuit has RFI problems **the sound will not be right if RFI is present!!** If such is the case then loading will have a beneficial effect.*

If a circuit does not have RFI problems then loading can still have a beneficial affect.

*The RFI is generated by the pickup and cable itself: it is not a matter of shielding from radio stations.*

Novel way of looking at a generator, or is it a transmitter? The oscillation or ringing occurs in the preamp because of the extraordinary amount of gain needed.

The tiny voltage of a LOMC still has inductance, which combines with cable and preamp capacitance and can cause HF ringing, but is only a problem with extremely low output carts with high resistance/inductance. I think such occurrences are beyond the bandwidth of your phono stages.

Saying RFI is generated by the cart is misleading. It is not. There are other loading considerations with MC's, none of which are about noise or tonality. You assume the higher the load, the better. I beg to differ. Such things as imaging, stage, dynamics, detail, and focus can all be affected by load, while tonality is unchanged.

Loading is very much about the cart and particular preamp.

Fleib, I recommend you do some design work and see if you still say that. You might also do a search on some of the comments by the Jonathan Carr (Jcarr) who is active on this forum.

If a circuit does not have RFI problems then loading can still have a beneficial affect.

Loading of LOMC cartridges has no effect whatsoever so far as the cartridge is concerned. There is a slight benefit to loading as low impedance terminations of cables reduces cable artifact, particularly with high capacitance cables. This is better realized if the cartridge is operating in the balanced mode (as it is a naturally balanced source) and the signal is carried through a balanced line. Then the cable will have no artifact at all. 600 ohms will be sufficient to eliminate the cable artifact.

Novel way of looking at a generator, or is it a transmitter? The oscillation or ringing occurs in the preamp because of the extraordinary amount of gain needed.

The cartridge/cable combo acts as both. It does not matter that the phono section has no bandwidth at the resonant frequency, which is usually several MHz. The gain has nothing to do with it.

The tiny voltage of a LOMC still has inductance, which combines with cable and preamp capacitance and can cause HF ringing, but is only a problem with extremely low output carts with high resistance/inductance. I think such occurrences are beyond the bandwidth of your phono stages.

I wonder if there is a semantic issue underpinning this conversation. In the above quote you are correct in almost every way except that there are no LOMC cartridges with high inductance... if it is assumed that by 'tiny voltage' you are referring to about 1.0mV or less. The inductance you thus refer to is the inductance in question, the frequencies are those in question, and no phono section I know of can go that high, but they don't have to- they only need to have an RF sensitivity and then you suddenly hear loading making a big difference.

Saying RFI is generated by the cart is misleading. It is not. There are other loading considerations with MC's, none of which are about noise or tonality. You assume the higher the load, the better. I beg to differ. Such things as imaging, stage, dynamics, detail, and focus can all be affected by load, while tonality is unchanged.

But here in your next paragraph you seem to contradict the earlier paragraph in the first sentence. I did not nor do I assume that the 'higher the load the better': I said the correct load and most designers design for 47K.

I agree that loading affects these things if your preamp has RFI problems! I don't know if you have ever heard what RFI can do to an audio circuit outside of a phono situation but the effect it can have on soundstage, background noise, detail and the like can be profound. As a result all I can assume from your reactions here is that the phono sections where you have tried different loading options are all having trouble with RFI; that is why you heard a difference! RFI has big effects on audio gear if not tamed.

I do however agree with your closing statement as loading has a lot to do with both the cartridge and the individual preamp, for the reason that the inductance of the cartridge and the resulting RFI affects different preamps differently. In our case since we got a handle in this some years back it has almost no effect which is good- its more plug and play. But we originally included the loading strip on our preamp (which is still there) because in the old days we heard differences with nearly every preamp we auditioned.

Here are some links that you may find interesting:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1281468389&openflup&18&4#18
and further down on the same thread:
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1281468389&openflup&22&4#22
pay attention to post number 3 at this link:
http://www.whatsbestforum.com/showthread.php?15077-Cartridge-Loading-A-Misnomer

Atmasphere,
I see you brought back up. The LOMC I was referring to are some of those coreless designs with very low output and high inductance/resistance relative to other MC. It was J Carr who told us about the HF oscillation/noise that could occur.

Regarding the notion that higher value loads are necessarily better, consider this:
If 500 ohms sounds good, and one tries 47K and it also sounds good but different, and both loads seem equally quiet, why is 47K better?
You're saying it is and you're wrong IMO.
Regards,

A LOMC cartridge without a core is going to have a lower inductance value as compared to one that does have a core. A core has a way of increasing the inductance, all other variables being equal.

As Jcarr points out in one of the links I provided, and IME, as you load the cartridge more and more the output goes down, which makes for more noise from the phono section. Generally speaking, the greater amount of noise the less low level detail due to the ear's masking principle.

In our preamps you really don't hear any difference with 500 ohms or 47K; our preamps are pretty immune to RFI. I've not been contesting that you don't hear an improvement- in fact I am quite sure you do. All I am saying (and all I have ever said in this thread) is that if so this indicates that your preamp has a problem with RFI. So in your case loading is important. But what works for you is not going to be the same for someone else with the same cartridge if they have a different preamp and tone arm cable. That was brought out in the links I provided.

I load everything at 47k these days as I now use an Atma-Sphere MP-3. I have tried different loading for my MC cartridges but hear no difference. I remember talking to Keith Herron several years ago at a RMAF show. I asked why his phonostgae did not have loading options. He pretty much gave the same answer as Ralph. Ironically though the next version of his phonostage did come with load options, but While he never admitted as much to me I think he did that for marketing reasons.

Atmasphere,
A coil with a magnetic core is more efficient so air core coils must be larger to get a usable output. The newer AT air core designs are the exception, probably using stronger magnets. Older designs like the DL-S1 have very low output and relatively high impedance/inductance.

OP has a Black Box, not a Herron or MP-1, and I would guess that some of what you say about to the higher usable value, might be appropriate, but it's not a rule.
One of my solid state phonos' has a much higher S/N, and it's obvious your loading "rules" are not always correct.
Regards,

The larger you make an air coil, the lower its inductance.
https://en.wikipedia.org/wiki/Inductor

The noise that a phono section has is usually not a function of loading. There are a lot of factors that have to do with noise- it is an immense topic.

The 'rules' are simply the laws of physics- and are impossible to violate.

All I was saying is that if you load a cartridge (like any other source), the result *can be* reduced output which will mean that the noise floor is higher.

Apropos of Atma's last two posts, last night I auditioned for the first time a newly acquired Ortofon MC2000 cartridge, one of the lowest of the "LO" MCs ever made. The MC2000 is said to have an internal resistance of 3 ohms, so a 100R load would seem to be quite appropriate. However, I inadvertently loaded it at 47K, as I began my listening session. This is using the phono section of Atma-sphere's own MP1 full function preamplifier. My MP1 has more than ample gain to accept the output of the MC2000 directly. In any case, I was blown away by my initial results. The MC2000 is one great cartridge, certainly one of the best sounding LOMCs I ever have heard in my system. After about 30 minutes of bliss, I noticed that I was running it at 47K, instead of 100R, which would have been my first choice. So I switched it over to 100R. With that load, it's still very good, but I think the sound lost some magic. The bass response was a little sloppy at 47K compared to 100R, but every other facet of reproduction was at least a little if not a lot superior at 47K. Pending further evaluation, I am a convert to 47K for LOMC, or certainly for the MC2000. I may try 1000R just to see if that tames the bass a bit, compared to 47K.

*The larger you make an air coil, the lower its inductance.*

In this case larger means more turns - higher inductance.

*The noise that a phono section has is usually not a function of loading. There are a lot of factors that have to do with noise- it is an immense topic.*

Okay. By the same token loading preference is not always a function of noise, as you contend.

Lew,
Congratulations on the new cart.
You might find that dynamics and stage get larger with a higher value load, and focus more precise with a lower value.

Sloppy bass would suggest a lower load. It might take some experimentation.
Regards,

Thanks, Fleib. Which is why I next intend to try the third alternative readily available to me, the way I have set up my MP1… 1000R, in hopes that it will provide the best tonal balance. But 47K is soooo good!

Of course, now I want to re-visit all my other LOMC cartridges to see what if anything I've been missing, to include Koetsu Urushi and Ortofon MC7500. Ironically, I purchased the MC7500 from Raul early on in the course of his MM thread. Then Raul always said his fave LOMC was the MC2000.

Hi Lewm,

I am a bit surprised at your preference of 47K for the MC 2000. I own two of them and find 47K a bit bright in my system. I much prefer 100 ohm. Do you know what the Nom. Capacitance (pF/ft) is with your phono cables?
Regards,

^^ this is how prevalent the cartridge loading mythology is!

Here is an explanation of why this cartridge may not have sounded bright in Lew's system:

http://www.whatsbestforum.com/showthread.php?14815-Best-phono-stage&p=307116&viewfull=1#post307116

Don, I did not (yet) say I prefer 47K. I did say I tried it by serendipitous accident and was surprised at how good it sounded with the MC2000, with the one exception that bass was a bit flabby. When I then switched to the gospel 100R load, I don't believe it sounded as open, free, undamped, dynamic, etc. Whatever adjective you choose, I thought the 47K load made the music sound more like real live music sounds. This was essentially on one Ella Fitzgerald original Verve album, the Berlin Songbook. Obviously, I need several hours more of listening to a wider variety of LPs before I would draw any conclusions. On the other hand, I am very familiar with this album on several different systems in my home.

Most people need an SUT with the MC2000, due to its very low output. If you are using an SUT, then the choice of a net 47K load is not really there for you. Let's say the SUT has 1:10 gain; you'd need a 4.7M load resistor on the secondaries in order to make the cartridge see 47K. Thus I don't wonder that most folks are loading down the MC2000 to around 100R, which in fact ought to be just fine, in theory, based on its 3-ohm internal resistance.

Don, The phono cables are the OEM cables supplied with the Kenwood L07D and L07J tonearm. These are very low in capacitance Litz type. I re-terminated them with male XLRs, for use with the Atma MP1.

Griffithds,
If the cart gets bright (change tonal qualities) with higher value load, it probably is as Atmasphere says. Not sure what good that knowledge will do. You'll load it down anyway.

Lew,
I take it that changing loads in the MP1 isn't that easy. I was thinking, perhaps something like 10 or 20K might tighten up the bass without sacrificing that glorious sound.
This is the preamp you modified for additional gain? Output appears to be 0.05mV.

I think I remember Jcarr recommending the MC3000 which looks similar.
Regards,

The MP-1 has loading strips mounted on the rear panel by the phono input. It might be one of the easier preamps to set cartridge loading.

Atmasphere is of course correct re the ease with which the load R can be changed on the MP1. I, however, never happy unless I am messing around, have installed a 4-pole, DT switch on the rear panel, such that I can choose among 3 load resistances without having to gain access to the rear of the preamplifier to change resistors, as is needed with the OEM set-up. With my switch in neutral position, the load is the basic 47K. With the switch in either of the other two (up or down) positions, the load is 100R or 1000R, respectively. Of course, both those values are in parallel with 47K, so the actual R is slightly lower than either 100R or 1000R. Should I feel the need, it is no problem to modify this arrangement. Truthfully, I am not at all sure that the flabby extreme low bass response I hear with the 47K load is per se due to effects of that load. It could be a tonearm/cartridge resonance thing. Anyway, it's really not objectionable compared to the other benefits.

Interesting: The URL offered by Atmasphere gives access to calculators for both RC and RL type filters. Using the RC calculator, I cranked in 150pF as an approximation of capacitance of my tonearm wire plus that of the phono input stage (which is a cascode and thus not sensitive to Miller capacitance, anyway). The equation itself tells you right away that fc is inversely related to both R and C; thus it is no surprise that when R = 100 ohms, fc is >10,000,000Hz. When R = 47K, fc comes down to ~22,000Hz. So if you look at it as an RC circuit, 47K would not make for a bright sound, compared to 100R. I then cranked the same values into the RL formula, were fc is directly proportional to R. I used 50 microHenries as an approximation of the inductance of the MC2000 (a typical value for a LOMC cartridge). Not surprisingly, in this case, when R = 47K, fc is much higher than when R = 100 ohms, but even with 100 ohms, fc is >300,000Hz. So again, 47K is not going to make for a brighter sound that we could possibly hear. In the actual situation, fc is a function of R, L, and C. Comments of Atma and Fleib, or anyone else, appreciated.

Running a typical MC cart. with a load of 47K is kind of like driving your car without shock absorbers. The inductance of the cart. in combination with the load capacitance forms a resonance circuit. With a 47K load and typical values for inductance and capacitance the peak is usually well past the audio band. The audio band may still be flat, but he response above the audio band will be rising. This will make the system more sensitive to surface noise and pops and other ultrasonic disturbances. If rise intrudes into the upper audio band any excitation of the resonance (ultrasonic surface noise and pops) will be made more audible.

Load the cart. down with a too small value resistor and the frequency response starts to drop in the audio band. Get it right and the response will be maximally flat. Load it with a high value resistor and get an ultrasonic peak in the response.

John, Please see my post above and Atmasphere's post above that. The numbers say that what you say is happening in the audible band is happening at way way higher frequencies than that. Can you offer the math? Aside from that argument, if you listened to an MC cartridge loaded at 47K, and if it sounded better in most ways at 47K than it did at some significantly lower value (higher load), would you then conclude that you had to change the load resistor to conform better to the theory, or would you say f*** it and just enjoy the music?

Then too, we have the arguments from Jonathan Carr, Allen Wright, and Ralph Karsten, not to mention other authorities we do not know about, all to the contrary of your position. I concede that all of those guys, as well as you, know more about the physics of the situation than I do, but there is an argument opposite yours, apparently.

These analogies between cartridge loading and automobile technology have their limitations.

thanks to Atmasphere, this is the most informative discussion of cartridge loading I've ever seen!

Lloydc, that may true but my head hurts. I have read and reread. Still do not fully understand. I no longer care about a complete understanding. Now I just wish to understand from my situation. If I turn the volume up two or three or four times the normal listening volume with the arm in it's Sadler, platter spinning, phono stage and integrated amp on with everything connected from the LOMC through sut to the speakers and there is no noise except air, do I not to need load? I mean no noise means no RFI? At least, I think that is the way I understand it.
Then again my head hurts 🌝🔫

There should be no tonal change with different loads. If there is, it's either RFI or intermodulation from that high frequency oscillation. In such cases all you can do is load it down or try another cartridge or phono stage.

Pkoegz, When you mess around with very low output cartridges, there are many sources of noise besides RFI. If you hear noise, a careful investigation is in order to try to reduce it or eliminate it, but in some cases, especially with an all-tube phono stage, you may just have to live with a faint background hiss. I find this not to be annoying, since it is really only apparent when the stylus is up off the LP or during silent passages between cuts on an LP. In the situation you describe, I would advise leave well enough alone. There is no reason at all to fuss with the cartridge loading, and moreover, the loading will have only an incidental effect if any on "noise".

I think you miss understood, I have no noise. I was just wondering if that ment I did not need any loading. Since posting I heard from the engineer/designer of phono and sut. He confirmed based on the cartridge I was using, he would not "use any additional loading". I am a happy😺

And a cool cat, too.

Pkoegz, its a good idea to try the loading at least. If it improves the sound (reduces brightness without affecting speed or bandwidth) then it tells you that despite low noise, the preamp is sensitive to Radio Frequency Interference (RFI).

This interference is generated by the pickup itself, as explained previously. If you hear little or no difference, then its no worries- the designer of the preamp has done his homework.

"These analogies between cartridge loading and automobile technology have their limitations."

In the old days before digital computers automotive companies use to model their suspension designs with analog circuits using inductors, capacitors and resistors. In the spring/mass system energy sloshes back and forth between the kinetic energy of the moving mass and the potential energy of the spring. In the electrical analog energy sloshes back and forth between the electric field in the capacitor and the magnetic field of the inductor. In the mechanical system the resonance is damped with a shock absorber, in the electrical circuit the resonance is damped with a resistor. Both systems are governed by the same differential equations. So the analogy is very apt.

The fact of the matter is a cartridge has inductance and forms a resonance tank in combination with the input and cable capacitance. The resonance peak will occur at a very high frequency, well beyond the audio band. Depending on the Q of the resonance you will see a rising frequency response well down in frequency from the peak. The Q of a resonance is determined by the source resistance of the cartridge and any load resistance. Now I will readily admit that if your phono pre is susceptible to RFI and your cart. is undamped, RFI will excite this resonance and raise all hell. That said, if your phono pre is not susceptible to RFI the resonance will still be there and the rising high end response it causes.

MC cartridges also have mechanical resonances that with some cart. need to be damped with a load resistor. Think speaker resonances and a low source impedance (high damping factor) amplifier.

But look, if you like the sound of your cart. running it wide open then go for it. Just don't make some kind of religion out of it.

John, I won't make a "religion" out of it, if you won't say I was making a religion out of it. The hostility in your response is inappropriate. I only relayed my preliminary and to me surprising observations; I did not say anywhere that I had found a new God or even that everyone in the world should use 47K as an MC load. A priori, I thought the same as you, and I probably don't even disagree with you now. I thought it was an interesting topic for discussion and that this thread was proper for discussing it.

As pointed out, the capacitance of the interconnect cable has a big influence and may actually be more important than the cartridge. That is why you can't have the same loading for all installations of the same cartridge.

If the cable capacitance is low, the resonance will be in the MHz region, in which case if the preamp does not care about RFI you simply won't hear a difference unless you load the cartridge so low that its output drops.

Atmasphere,
*If the cable capacitance is low, the resonance will be in the MHz region, in which case if the preamp does not care about RFI you simply won't hear a difference unless you load the cartridge so low that its output drops.*

If capacitance is low, and if preamp does not care about RFI, then you won't hear a difference with what, change of load, change capacitance?

What are you talking about?
If you're saying resistance load makes no difference in the absence of noise, you're wrong.

*That is why you can't have the same loading for all installations of the same cartridge.* (cable capacitance differences)

With RFI absent, why not?
Of course you can.
Regards,

Capacitive loading will make a difference- its the same as using a more capacitive cable, which is to say its probably something you want to avoid as it will lower the resonant frequency of the RF circuit.

A capacitor can be quite useful in loading MM cartridges however, but this thread so far has been about LOMC cartridges.

If you're saying resistance load makes no difference in the absence of noise, you're wrong.

Pretty sure I didn't say anything like that. But to address the comment, loading can indeed affect noise because if the preamp is susceptible to RFI, eliminating the RFI very frequently will reduce noise it can cause.

Again, if you find that loading is improving your noise floor, its likely that your preamp has problems with RFI.

And not to repeat myself too much but also again, if the load is too severe (too low a value) it can have the effect of degrading your noise floor on account of the fact that it is reducing the output from the cartridge.

Now this means that loading can be a bit tricky if the preamp has RFI problems because it is not predictable what the right loading value will be on account of the interconnect cable. Things become a lot easier when the preamp resists RFI- then all you do is keep the cable capacitance down and life is good.

I suppose if you were to use a transformer placed close to your TT to keep leads very short you could push the resonance up past 1mHz. In a more normal situation I would guess it would be hard to push cable and input capacitance much below 100pF. Without an input transformer the input stage would have to be probably a cascode for the high gain needed without getting killed by the Miller effect.

A cartridge with 5mH inductance in combination with 100pF has a resonance of 225kHz. A typical system may have more like 200pF. This results in a resonance of 160kHz. A sharp impulse like from a scratch will generate a lot of high frequency harmonics and could conceivably excite the resonance and cause it to ring generating bursts of high frequency noise. Now as long as your phono pre is hunky dory dealing with bursts of high frequency signal (no IM with audio signal, or maybe it shunts these signals to ground with a ceramic disc cap at the input?) you're good. The 75uS time constant will roll this stuff off, usually after the input stage. In the above examples the resonance is 6 to 7 octaves above 2.122kHz so the ringing will be attenuated by 36dB - 42dB (unless your phono stage uses the 4th pole and shelves the response at 50kH). Not gone by any means. Could still pollute gear downstream. That said, there is enough going on that in the end one's own ear should be the final arbiter.

Some might find the thread below interesting.

thread