Effects of MC Loading

[JP]

Time for some fun!

I often see writings about the audible effects of MC resistance loading, which don’t appear to comport with the technical aspects of an MC generator or my own experiences. I’ve done fairly extensive audible testing on this in the past but have decided to re-create some of it and make it available.

Below are four collections that contain laybacks of a Lyra Kleos loaded at 1k, 100R, 10R, and 1R. The cartridge’s spec’d DCR is 5R5. The only processing was to remove ticks that didn’t appear on all four laybacks in a group (there were about six in total) and to match levels.

Hopefully you can do better than I did!

Bill Evans
Norah Jones
Steely Dan
Smashing Pumpkins


@Mr.6L6 - per our earlier conversation.

 

[Grbluen]

Time for some fun!

I often see writings about the audible effects of MC resistance loading, which don’t appear to comport with the technical aspects of an MC generator or my own experiences. I’ve done fairly extensive audible testing on this in the past but have decided to re-create some of it and make it available.

Below are four collections that contain laybacks of a Lyra Kleos loaded at 1k, 100R, 10R, and 1R. The cartridge’s spec’d DCR is 5R5. The only processing was to remove ticks that didn’t appear on all four laybacks in a group (there were about six in total) and to match levels.

Hopefully you can do better than I did!

Bill Evans
Norah Jones
Steely Dan
Smashing Pumpkins


@Mr.6L6 - per our earlier conversation.

I played around with loading in moving coils and didn't notice any changes other than levels. The Lyra specialist mentioned that the loading only affected radio frequencies. This discussion was over at
Audiogon. I don't want to start a flame session, but I don't try to adjust the sound with the loading. Ymmv

 

[Mr.6L6]

This is truly fascinating! Thank you for posting.

 

[tabarddn51]

Loading can have an affect on MC sound. I prefer to play my 103 at 950ohms as it brightens the top end a little, which in-turn helps base impact. However it's this never ending story, none of us hear the same, so many people may not.

Cheers

 

[JP]

Didn’t listen to the files then?

 

[mr_petit]

Only did the complete steely dan test, as doing these tests are quite intense for me (I take them seriously, probably switching 100 times or more per choice, as the difference is not there...)

I don't have 1st hand on LOMC or loading of those carts, but calculations show that it's usually way way out of the ears reach (unless you maybe go ridiculously low R).
I know I have a pretty trained ear, and every choice in this test was 100% a gamble. Statistically I should've done slightly better I see, my performance is rounded off to the low side..2 instead of 3 .
I can't imagine anyone scoring a statistically sound result on this one (like 75% or so)
Good test. proven point

Given that it makes no real difference, I think it's strange that lots of preamps usually have loading resistance choices for MC but not for MM. For my AT-440mla I sometimes choose ~35k as optimal loading, certainly with cables that don't have very low capacitance


That all said, I think generally on forums way too much is discussed and argued in text and way to little by means of listening.
The quality of the samples is epic. Very good sounding cartridge, nice bass. Sadly not my price range.
Listening to the Smashing Pumpkin samples, I can do the test, but it'll be 100% a gamble again, so statistically I would now score 3 correct...
Also with the other samples... I hear absolutely no difference.

 

[JP]

Only did the complete steely dan test, as doing these tests are quite intense for me (I take them seriously, probably switching 100 times or more per choice, as the difference is not there...)

I don't have 1st hand on LOMC or loading of those carts, but calculations show that it's usually way way out of the ears reach (unless you maybe go ridiculously low R).
I know I have a pretty trained ear, and every choice in this test was 100% a gamble. Statistically I should've done slightly better I see, my performance is rounded off to the low side..2 instead of 3 .
I can't imagine anyone scoring a statistically sound result on this one (like 75% or so)
Good test. proven point

Given that it makes no real difference, I think it's strange that lots of preamps usually have loading resistance choices for MC but not for MM. For my AT-440mla I sometimes choose ~35k as optimal loading, certainly with cables that don't have very low capacitance
View attachment 3104173

That all said, I think generally on forums way too much is discussed and argued in text and way to little by means of listening.
The quality of the samples is epic. Very good sounding cartridge, nice bass. Sadly not my price range.
Listening to the Smashing Pumpkin samples, I can do the test, but it'll be 100% a gamble again, so statistically I would now score 3 correct...
Also with the other samples... I hear absolutely no difference.

I may do another run with a cart that has a higher DCR and inductance. Even at 1R load, the HF roll-off is going to be a fraction of a dB on this one, though I still think inaudible in nearly all normal cases. The other aspect of this test is the notion of loading damping the cantilever, which was the impetus for putting this series together.

There's a school of thought that loading options can help if the phono stage has poor immunity to RF interference - Ralph Karsten tends to be a proponent of this. And of course, as mentioned above, that it can affect mechanical damping, for which I've never seen any reasonable evidence. There's also an aspect of giving the market what it thinks it needs/wants.

The Kleos is nice, but all of my better MMs track better - there's one spot on the Norah layback where it hit the ragged edge of what it could track (not associated to loading). It has the typical mid dip/upper-mid boost that's so popular these days, but rather subtle so it doesn't present as obviously colored to me. All the same, after listening to it for many hours I swapped to a V15-VMR as I had to do some critical comparisons of something, and it was a relief to get back to neutral.

This is the Steely Dan set with level differences between the different loadings preserved, with 30R added. All these differences should audibly present except between 1k and 100R, though only 1R is plainly obvious as a level difference.

1k: -0.00dB
100R:- -0.38dB
30R: -1.56dB
10R: -4.24dB
1R: -17.35dB

 

[mr_petit]

There's a school of thought that loading options can help if the phono stage has poor immunity to RF interference - Ralph Karsten tends to be a proponent of this. And of course, as mentioned above, that it can affect mechanical damping, for which I've never seen any reasonable evidence.

I'm not really sure I understand what you mean here.
You mean that radio frequency electro magnetic radiation interference can be influenced by loading and that that affects mechanical damping in the cartridge?
Like maybe on a normal amplifier the damping factor forms a system with the Qes of a loudspeaker and influences the (electrical) damping?
Could you elaborate on this?

There's also an aspect of giving the market what it thinks it needs/wants.

That is the base existence of both the audiophile and audiophool market

The Kleos is nice, but all of my better MMs track better - there's one spot on the Norah layback where it hit the ragged edge of what it could track (not associated to loading). It has the typical mid dip/upper-mid boost that's so popular these days, but rather subtle so it doesn't present as obviously colored to me. All the same, after listening to it for many hours I swapped to a V15-VMR as I had to do some critical comparisons of something, and it was a relief to get back to neutral.

Too bad tracking is mediocre when the grooves become difficult, especially at that pricepoint.
Imho where cartridges make the difference is in only 5-10% of the music on a record, those difficult to track sections (usually inner grooves). So we buy the expensive cartridges/stylii for only 5-10% of our listening time.
But there's nothing more annoying than enjoying music and on the next track it suddenly starts to sound bad

 

[rothwellaudio]

There's a school of thought that loading options can help if the phono stage has poor immunity to RF interference - Ralph Karsten tends to be a proponent of this.

I'm not really sure I understand what you mean here.
You mean that radio frequency electro magnetic radiation interference can be influenced by loading and that that affects mechanical damping in the cartridge?

The cartridge has an output impedance of a few ohms in series with a very small inductance. The load that the source sees is a resistance in parallel with some capacitance. The source and the load form a resonant circuit, and with "typical" values the resonance is well above the audio band, maybe falling somewhere in the low RF band. Lowering the resistance of the load impedance has almost no effect on the audio band but can damp the resonant peak lying in the RF band.

And of course, as mentioned above, that it can affect mechanical damping, for which I've never seen any reasonable evidence.

The principle involved is quite straightforward - it's based on Lenz's law, ie a lower load impedance allows more current to flow in the coils, which in turn creates more back EMF which opposes the motion creating the current. So in theory, yes, a lower load impedance creates a damping effect. In practice? That's debatable, because the damping effect of the stylus suspension also comes into play. Does the damping due to stylus suspension completely swamp the damping due to Lenz's law? To be honest, I don't know. I've never seen any calculations or any measurements which offer any credible evidence either way.

There's also an aspect of giving the market what it thinks it needs/wants.

Yes, I'm sure that's a factor. Judging by many of the comments on forums anyone would be led to believe that the correct load impedance is crucial to get the correct tonal balance from a LOMC cartridge. There's no theoretical basis for that belief, and as your experiments suggest, there's plenty of empirical evidence to the contrary.

 

[JP]

I'm not really sure I understand what you mean here.
You mean that radio frequency electro magnetic radiation interference can be influenced by loading and that that affects mechanical damping in the cartridge?
Like maybe on a normal amplifier the damping factor forms a system with the Qes of a loudspeaker and influences the (electrical) damping?
Could you elaborate on this?

As @rothwellaudio said, but will add that the issue is purported to be with circuits where the resonant peak causes an issue with the stage, such as an ultrasonic overload, which can then cause IMD in the audible band. I've not seen any particular products cited for this problem, and none of the MC stages I use have this issue, so it's not something that I've looked in to further.

Regardless, this experiment isn't to say that there can't be an effect, rather that evidence would show that if there is one, it's not solely the cartridge.

The principle involved is quite straightforward - it's based on Lenz's law, ie a lower load impedance allows more current to flow in the coils, which in turn creates more back EMF which opposes the motion creating the current. So in theory, yes, a lower load impedance creates a damping effect. In practice? That's debatable, because the damping effect of the stylus suspension also comes into play. Does the damping due to stylus suspension completely swamp the damping due to Lenz's law? To be honest, I don't know. I've never seen any calculations or any measurements which offer any credible evidence either way.

Most people that have considered the efficiency of the generator state single-digit numbers, and a good share of those somewhere sub 1%. Ironically even one that claims there is an obvious audible effect estimates efficient at less than 1%. A fraction of a percent of a fraction of a percent is pretty small. Regardless of the physics, empirical testing for audibility is rather easy. I think the most obvious thing that people miss is that levels have to be matched as small differences are perceived as tonal.

 

[JP]

Too bad tracking is mediocre when the grooves become difficult, especially at that pricepoint.
Imho where cartridges make the difference is in only 5-10% of the music on a record, those difficult to track sections (usually inner grooves). So we buy the expensive cartridges/stylii for only 5-10% of our listening time.
But there's nothing more annoying than enjoying music and on the next track it suddenly starts to sound bad

The only place it had an issue was on one spot on the NJ track, and I've read that the AP version is supposedly a bit of a test. I was surprised as I'd never had an issue tracking that with my other cartridges, but I don't typically do fashion stuff. I didn't bother increasing VTF above the recommended high-side as it's not my cart and is already on its way back home.

 

[mkane]

interesting thread thanks

 

[Ilikevinyl]

Loading can have an affect on MC sound. I prefer to play my 103 at 950ohms as it brightens the top end a little, which in-turn helps base impact. However it's this never ending story, none of us hear the same, so many people may not.

Cheers

Tried 1K, 660 and settled on 475 ohms with my DL-103. Loading it higher, bass is thinner. Music has a slight glare to the sound at 1K. At 475 ohms the music has more meat to the sound, punchy bass. Sounds perfect at that setting.

 

[mr_petit]

As @rothwellaudio said, but will add that the issue is purported to be with circuits where the resonant peak causes an issue with the stage, such as an ultrasonic overload, which can then cause IMD in the audible band. I've not seen any particular products cited for this problem, and none of the MC stages I use have this issue, so it's not something that I've looked in to further.

I wonder how likely this is too. I mean, how strong is this resonant peak?
I don't have a lomc currently, but I measured the resonance peak from my Denon DL-160 (HOMC) with 47k and 220pF.
And it's little over 4.1dB (at little under 500kHz).
So that is 4.1dB over the background signal noise or whatever excites that resonance.
I can't imagine that causing for problems in the phonopre (4dB is not shocking and I imagine 4dB in backgound interference is even a normal margin between situations and setups).
And with a LOMC generally having a way lower resistance loading, that peak resonance is probably lower? Do you have any data on that?


This is the bode plot of the DL-160 and it's resonance:



At first I just wanted to inject noise and look at it with FFT but nothing showed up, the FFT function of my DSO is probably not accurate enough for that. Luckily it can do automatic bodeplotting too.

Regarding the mechanical damping with a low loading resistor: how would you measure that?
I couldn't hear anything. I also wonder if it's worth the loss of signal and therefore worse s/n ratio. I couldn't detect more noise in your samples, but of course the samples weren't quiet passages in music, and results will of course also vary dependign on how quiet the phonopre is.

 

[rothwellaudio]

I wonder how likely this is too. I mean, how strong is this resonant peak?

I don't know. I wasn't claiming that LOMC cartridges suffer from ultrasonic resonance and it must be addressed, I was just explaining the theory behind such claims. It's now clear that you understand the theory anyway.

Regarding the mechanical damping with a low loading resistor: how would you measure that?

I've stated numerous times on this forum that the effects of loading on a LOMC cartridge are wildly exaggerated. That isn't a popular opinion so I usually just keep my mouth shut.

 

[mr_petit]

That isn't a popular opinion so I usually just keep my mouth shut.

Well now you can refer to these blind tests and have people who feel really strongly towards this post their results (that said, the links (the abxtests.com site that is) are currently down).

 

[JP]

Shoot, didn’t know it was down. I may have to host it myself.

 

[JP]

Regarding the mechanical damping with a low loading resistor: how would you measure that?
I couldn't hear anything. I also wonder if it's worth the loss of signal and therefore worse s/n ratio. I couldn't detect more noise in your samples, but of course the samples weren't quiet passages in music, and results will of course also vary dependign on how quiet the phonopre is.

There were some experiments on diyAudio with an MM IIRC - short a channel and watch the impact on the opposite channel. I haven’t repeated the experiments with any magnetic type as I find it to be pointless - nothing supports the notion, and audible differences are plainly explained by the lack of basic controls.

 

[mr_petit]

short a channel and watch the impact on the opposite channel. I haven’t repeated the experiments with any magnetic type as I find it to be pointless -

It's still an interesting test to perform.
I also don't expect any measurable results, also considering loading it down to extremely low resistance load is not something that is done in practice, so going below 10 ohms just causes other problems. And I also expect the efficiency of a cartridge to be extremely low. Well below 1% (looking at how low efficiency of most speakers are with in comparison huge magnets (in case of mm) and coils (in case of lomc)
But the proof of the pudding is in the eating

 

[lini]

(...) but I measured the resonance peak from my Denon DL-160 (HOMC) with 47k and 220pF. (...)

Just curious: How did you measure that, btw?

Greetings from Munich!

Manfred / lini