Running LOMC with MM (47K) loading

Perhaps the Pass is one of those phono stages that's not that sensitive to loading.

Yes. Nelson knows what he's doing.

However I suppose it could also be an option for the customer who needs to tame their systems tendency towards brightness. At least that was an early finding I had with some different components. Thanks

Its not always an option to seek out a phono section that doesn't have this problem! So loading will probably be a thing for the foreseeable future.


For me the big thing is ticks and pops. I don't like them. A phono section that doesn't require loading at the input is also far less likely to generate ticks and pops on its own, caused by a poor high frequency overload margin at the input of the circuit.

You load the cartridge to what sounds good to you on your system and every system is different it is not a band aid but a load as you like it

Its a band-aid in the sense that if the phono preamp doesn't have a problem with RFI injected at its input, you'll find that loading doesn't affect the sound nearly as much. So you'll be able to run with the stock 47K and it won't be too bright.

we don't affect what the cartridge does at all (unless the value of the load approaches or drops below the internal impedance of the cartridge). What adding resistive loading at the phono stage input accomplishes is to dampen the resonant energy of the ultrasonic spike, and give the phono stage an operating environment that isn't so likely to trigger any latent non-linearity tendencies that the phono stage circuitry may have.  

For the reasons given, the phrase "cartridge load" is misleading. "Phono stage input terminator" is a better description of what really happens."

I am wondering what aspects of his comments you agree with or disagree with. I regard you both as experts in this field.

I agree with Jonathan. He commented to me when we met at Munich a few years ago about how loading can affect the compliance of the cartridge and I have to admit I'd given it no thought until he brought it up. My main concern since the early 1990s about using loading as a solution is that its a bandaid for a phono section that has problems with RFI injected at its input. He is probably correct that the loading won't affect the cartridge very much until the load is near that of the impedance of the cartridge itself (at that point the output of the cartridge falls off). The winding in a cartridge

But it *does* affect the mechanical resonance of the cartridge in the tonearm and this in turn can affect how the cartridge tracks, as you want that resonance to be between 7 and 12Hz.  But for the most part you can certainly get the cartridge to track in many arms while driving a lower resistance load. Its simple physics that the cantilever will be stiffer. How that affects things will vary depending on the cartridge, arm and load resistance used. 

47 kohms is for moving magnets. I would use what is recommended by the cartridge manufacturer. My hana el calls for >400 ohms, I use 430. Not certain why you would exceed the value by 10's of thousands.

47K is the industry standard for all cartridges, MM or LOMC.

damping is not required for most MC cartridges (because their resonant peaks are now well outside of the audible range) except if those peaks result in overloading of the phono stage. 

^^ This. Overload of the input section of the phono stage can result in ticks and pops. That is a very real argument for looking for that phono section that does not require a load!

I don't see any mechanism for the electrical loading somehow affecting the mechanical movement of the cantilever. The loading acts as a voltage divider with some fraction of the signal diverted through the resistor to be dissipated as heat. 

Its not a feedback mechanism. You are working with a misconception. The loading is not a voltage divider; its directly across the output of the cartridge and in the input of the phono section.

When a magnetic motor or transducer is loaded, it has to do more work. That work comes at a price: its harder to make the transducer move. You can prove this easily to yourself because a loudspeaker is a moving coil device not unlike a cartridge (and can be used as a microphone in a pinch). Remove the speaker cable from the speaker and remove the grill cloth. Push on the woofer and see how easy it is to move. Now put a quarter across the speaker terminals so as to short them out. Try to move the woofer again. You'll see its less compliant. The same thing happens when you load a cartridge. Its simple physics. This was put more succinctly:

It is common knowledge that when you ship a speaker, you should short the terminals because it provides a "dynamic brake" which limits cone excursion from sudden impacts. A cartridge is simply a speaker in reverse and loading a MC can have a dynamic impact on the compliance.

In the case of the cartridge, where is the back emf or back emf increase by adding a loading resistor to the circuit? If there is any sort of back emf induced in the moving coil, it would be so negligible compared to the forces acting on the cantilever.

Because the cartridge is a transducer producing voltage from physical movement, there is no back EMF like there is in a speaker which is doing the exact opposite! The 'EMF' in this case isn't 'back', its 'forward' which is to say it **IS** the signal :)

When a cartridge manufacturer specifies a load less than 47K, its because they either don't realize that the load is really affecting how their reference preamp works, or more commonly, they know they can't predict which tonearm cable and phono preamp you are using. Because most phono preamps have stability problems, its wise for them to make some recommendation. They are probably assuming that the tonearm cable is only a meter in length, which in turn tells them that the capacitance of the cable probably does not exceed 100pF, since getting over 30pF/foot is unwise in a phono cable.