Cartridge Loading- Low output M/C

"Magnetic cartridges are the only cartridges that might be affected by cable capacitance. With moving coil cartridges, cable capacitance is not a concern."

Is the above a true statement?

No. It is advantageous to keep the resonant frequency as high as possible.

^^ Sounds like it to me :)

Between 475 and 100,000 ohms I must confess that the differences I think I hear in the music are so small they may be imagined. Is this to be expected or should I run immediately to a good Otolarygologist?

About 30 years ago I worked on developing a box that would allow a person to know what the right loading value for a LOMC cartridge actually was. To this end, I had to pass squarewaves through the cartridge, as the proper loading would be that which prevented 'ringing' a harmonic distortion caused by the fact that the cartridge is an inductor.
To my surprise, I discovered that any LOMC could pass a 20KHz squarewave regardless of loading. The only thing that changed was if the loading value was reduced too much, the output went down.
That was when I realized something else was afoot with loading. Its not the cartridge, its the preamp that is reacting, as described elsewhere in this thread (the loading box concept was thus abandoned).

Some takeaways (all previously covered):
1) If your phono section requires loading to sound right, it is due to an overload margin problem, inherent instability of the circuit, or both.
2) If the circuit is unstable, you will experience more ticks and pops that sound like the LP has a noisy surface.
3) the loading will decrease the compliance of the cartridge, which in turn will reduce its high frequency response. How much is hard to say, but some people (myself included) have heard loading act like a tone control, and this may be part of the reason why, since under normal circumstances, the RF peak that results is usually well outside the audio band unless a MM cartridge is used or the tone arm cable has crazy high capacitance. 

This may not be an issue, but it would seem to me that when using a high resistive load an input amp with either a very high overload margin or a deliberately limited bandwidth (<<2.5MHz) would be essential. Once again, preamp architecture seems to be the deciding factor.

It is an issue, as far as I can tell. Overload margin is really important otherwise ticks and pops abound.

When you cut a lacquer, if the stylus angle and temperature are set right, the silent groove is so quiet that the playback electronics are the noise floor. The test LP you get back from the pressing plant comes with a form that the producer has to sign- so the test LP gets a listen to insure an absence of ticks and pops. So it follows that most LPs should be nice and quiet, and in practice if the phono preamp is up on its game, they will be.
I don't have the values you requested, but the coil at the output of the cutter amps isn't very large. The inductance of the head varies depending on the voice coil used and we've used both. The older version use a series resistance, while the newer ones are higher impedance (about 10 ohms) and don't employ the resistor. I suspect this could be handled in a better way, as well, the cutter amps were designed in the late 1960s- they are pretty primitive!

We have arguments about this all the time as he feels so sure that his A810 with NE5532 opamps galore in the playback path is so superior to LPs and he often cites the limitations described to him by the mastering engineers.
I assume that the 42kHz cut off isn’t a single pole- and I also assume that it uses some kind of relatively benign analog filter like a butterworth or gaussian.

Actually the 42KHz is just handled by a single choke in series with the cutter head!

So, perhaps the answer to the loading question is, no matter how unlikely it seems- it depends on the architecture of your phono amplifer!

+1

I’ve always preferred passive EQ as it seems to result in a more stable preamp. I’ve maintained that a lot of ticks and pops heard in many phono sections are actually the phono section misbehaving (due to oscillation) and not actually audible ticks and pops on the LP surface; your modeling *seems* to confirm that (please correct me if I am misinterpreting your data). To that end, I’ve often recommended that one look into the matter of cartridge loading; if the preamp does not seem to need the input load and is alright with the resulting (RF) peak, then a pretty important side benefit will be less ticks and pops.

In non-opamp circuits, the presence of stopping resistors at all input nodes of the active devices in the circuit seems to play a role (many Japanese phono equalizers from the 60s-80s had no stopping resistors at all; not surprisingly they seem to exhibit more ticks and pops). So I don’t think that feedback is the destabilizing factor as I know of phono equalizers that are well behaved (no need of loading, no ticks and pops) that employ feedback EQ. I too feel that topology plays a huge role!

The recording process (particularly analog) imposes restrictions in the frequency response- limiting the HF and LF responses. These restrictions are not set in any standard and are usually due to limitations in the equipment used (Tape recorder and lathe frequency responses and dynamic ranges for examples). Good recording engineers try to minimize the effects, but they still exist.

Hello Wyn, when I saw this comment, because I run a small LP mastering operation, I thought you might like to know that the bandwidth of most LP mastering systems can go pretty high (and down to about 5Hz). Our Westerex system is bandwidth limited by a filter on the mastering amplifiers at 42KHz. This is mostly done to prevent damage to the cutter head from errant signals at the input, since the RIAA preemphasis causes a wee bit of extra gain at that frequency!  As far as dynamic range is concerned, the limitation of LP dynamic range is on the playback side, not record (although many LPs are compressed, this is mostly due to the fact that if no compression is to be used, the mastering engineer will have to spend a bit more time with the project, so compression is there to save money, not because the LP format can't do it). The cutter head can easily cut grooves that no modern arm/cartridge combination could track; the mastering engineer's task is to make sure that the cutter head does not exceed those playback limits!
Just to be clear about the effects of RFI on a preamp, the designer's concern is not so much about RFI from external sources like a radio station (although that certainly is a concern) but the RFI generated by the cartridge and interconnect cable combination (and also the input capacitance of the preamp itself). If immune to the latter, it will also be immune to the former.

Atmasphere- I appreciate all your insight and help. I currently have no ticks and pops with my analog setup.VPI Prime-Plinius Koru-Pass Labs Integrated 60 -Phono Cable is VPI with ground-Interconnect from Phono pre to the Pass Integrated is AudienceAU 24 i XLR. BTW my cartridge is an Ortofon Black Quintet.
With that said...because I have no issues currently-does this suggest that I have a stable phono section?

To your question, if with 47K as a load, then yes :)

larryi makes a good point, +1:

utilizing high loading (low value of resistor) takes away a lot of what one hopes to get out of moving from run of the mill MM cartridges to a MC cartridge--the vibrancy, liveliness and top end extension is wiped away.

Raul, All you have to do is have a stable phono section. I'm not the only one that makes one by any means. JCarr is aware of this issue and he offers phono sections as well. Nelson Pass seems to be as well, his phono sections work without ticks or pops too. I think we can add Jim Hagerman to that list. His website has a lot of useful information on this topic:http://www.hagtech.com/loading.html
It seems to me that the real problem is that you now realize that you have ticks and pops and now you know a reason for it that you didn't before. That sort of revelation usually doesn't sit well with a person that likes to think they have everything sorted out.

There is a massive misunderstanding that seems implicit with Raul's post, which is not surprising since Raul  prefers digital audio... no idea why he posts here.

This is not about money, its the physics of why its worth it do to it right, which does not cost any more. If your phono section is requiring that you use loading resistances, follow my suggestions here and above.

Input capacitance is a thing with all phono sections. It can be considered to be in parallel with the cartridge inductance, and so reduces the resonant frequency that is always present, which should be kept as high as possible. If ever there was an argument for a vacuum tube input, this might well be it, since tubes have far less input capacitance.
Alternatively, if one were to use a stepup transformer, the transformer blocks the RFI resonance due to bandwidth limitations and may well be why some people prefer using an SUT with their phono sections. SUTs are their own bag of tricks- to get them to work right, they have to be loaded at their output to prevent the transformer from ringing (distorting). This value is different for every cartridge as each cartridge has a different impedance and transformers transform impedance. Usually the transformer manufacturer will have an idea of what the correct loading will be (a good example in this regard is Jensen, who also makes some of the best SUTs made).

At any rate, keeping the cable capacitance low is important for proper phono reproduction! @krelldog , there are no specs (just 'features') on the page you linked.

If no SUT is used, one should always start with 47K since that is the industry standard and has been for decades. This value is used because its less susceptible to noise that a higher input impedance might be, while easily driven by moving magnet cartridges which are very susceptible to loading at audio frequencies, unlike moving coil cartridges (unless the latter is high output, since its the inductance that causes the susceptibility). From there reducing the loading resistance can be explored if needed.

**The highest value you can use is recommended for best results.**

That can be considered a general rule of thumb.

Again, if the phono section is unstable or has poor overload margins the result will be more ticks and pops. People often ask me how I get such low noise reproduction without ticks and pops and that is the secret. Many people grew up with unstable phono sections (most Japanese phono equalizers made during the 60s, 70s and 80s were unstable) and so just assume that ticks and pops are part of the LP experience, but it does not have to be that way.

The OP is asking for loading and not why many phono stages works in different way when we make load values.

Who cares, he as any one of us already owns a phono stage it does not matter what and no one can make a world research to find out which phono stages works as should be, it's imposible to do that.

So, what each one of us have to do is to load our cartridges according what we have and according each one music/sound priorities. That's all.

@krelldog You can safely ignore Raul's remarks in this matter. Most of the remarks above are false.

My prior comments were about the theory behind how all this works.
Regarding your situation, it is advisable to run the least amount of loading possible (by least, meaning the highest resistance with the least capacitance). To this end, you might see if you can find out what the capacitance is of your tone arm cable. If you can find a cable with less capacitance, it might sound better even though it might also be less expensive. A shorted cable will of course have less capacitance- for example cutting your cable to half of its length will double the resonant frequency (assuming no input capacitance in the phono section; some solid state phono sections have quite a lot of input capacitance due to the capacitance at the gate or base of the first semiconductor used). The more capacitance the cable has, the lower the resonant frequency and its best to keep the latter as high as possible.
If it just does not sound right with 47K as a load, I would use the highest loading resistance available to you that takes the edge off. I've not played with every Krell phono section but those I have have been unhappy without loading, suggesting an unstable phono section. The actual goal is not only tonal neutrality, but **also** the least ticks and pops. When you load at a very low value (like less than 100 ohms) its possible to reduce the cartridge output and also decrease high frequency tracking abilities. So this should be avoided if at all possible.
There is no 'set' value of loading that can be specified by any cartridge manufacturer (and suggestions from other audiophiles won't be ideal either). This is because they cannot predict the tone arm cable capacitance nor the input capacitance of the phono stage (ours tends to be quite low as this has been on our radar for decades). So the values you see cartridge manufacturers suggest are always generalities, as they can't assume that a given phono section is stable. But at the same time, this is also why 47K is suggested and is the industry standard- because its really all that is needed if the phono section is properly designed. 

@krelldog
If the cartridge needs loading below 47K its an indication that the preamp is not stable with Radio Frequency Interference (RFI) at its input.

The loading resistor is not for the cartridge, its for the preamp.

This is because the cartridge inductance combined with the tone arm cable capacitance forms a tuned RF circuit- which is energized by the cartridge signal. It can be over 30 db higher than the phono signal- thats about 1000x more powerful!
The loading resistor detunes the RF circuit, preventing the RFI. The problem is that in so doing, the cartridge is asked to perform more work as it has to drive the lower resistance. This makes the cartridge cantilever stiffer and less able to track higher frequencies. This is why the resistor can act as a tone control.

A side problem is that preamps that have problems with RFI are also far more likely to produce ticks and pops. This is often due to poor overload margin, since a signal that is 1000x more powerful can overload the preamp. The other reason is that the phono circuit can be unstable and react poorly to RFI; either way if the phono section does not have these problems, a side benefit is far less ticks and pops- you may not ever hear any on an entire LP side.
Many phono preamp designers don't realize the RFI implications and so don't know to make sure their circuit is immune to these problems. So instead you see loading switches and the like...