Cartridge Loading for a phono pre amp

I use an ARC Ref Phono 2SE balanced into a Ref 5SE. With an MC cartridge, the difference between 47K and 100 ohm loading is virtually undetectable and may even be zero. (You can use the Ref Phono remote to change loading from your listening chair.)

Why ARC featured such function in their reference phono stage that serve no purpose? So they can charge more?🤔

I have a Benz Micro Glider rated at 1.1MV

I think your Glider is the SM ( medium output level) with 24 ohms resistance and recommended loading is 240 ohms or higher.

If 100 ohms loading is too low and 470 ohms is too high, you can turn on both 470 ohms and 560 ohms to get approximately 250 ohms loading.

https://benzmicro-northamerica.com/benz-micro-glider/

Although theoretically loading will affect the compliance of the cartridge, and 100Ω loading made the cartridge work 470 times harder than 47kΩ loading. But since the coil resistance is much lower than the loading resistance, I think the effect on the cantilever stiffness is insignificant. Therefore the test result show no difference, IMO.

Since RFI is not the music contents, so apply a correct amount of resistive load to damp the unwanted RFI is not an bad idea after all. Again, IMO.

The options I have are as follows: 47K, 1K, 560R, 470R, 100R, and 47R.

There are three more options worth experiments:

257R (560R+470R)

322R (1K+470R)

362R (1K+560R)

What the load resistor does is three things: it detunes the resonant peak I mentioned earlier, thus eliminating the RFI and it causes the cantilever to be stiffer, possibly reducing the ability to trace high frequencies and certainly affecting the mechanical resonance of the cartridge and arm combination.

So you solve a problem for a phono section with a design bug, in exchange for introducing possible tracking issues. Not a good set of options IMO.

@atmasphere 

Since almost all MC cartridge manufacturer provide recommended minimum loading resistance, and usually the value is 10 times higher than the cartridge coil resistance.

My question is how significant that affect the cantilever to be stiffer and introducing possible tracking issues, OR its effect is negligible?

And may I ask how you fix that issue in your phono stage design?

@rauliruegas 

Please calm down, PLEASE!

This is a discussion forum, everyone is entitle to share their opinion and knowledge. If you disagree with somebody's responses, you're entitled to counter response! Why not be a gentleman and stop name calling? I believe all members of this thread are appreciated it.

Your target for mechanical resonance is between 7-12Hz. The mechanical resonance is a product of the mass of the cartridge in the arm vs the compliance of the cantilever of the cartridge. Changing the load from 47K to 100 Ohms can easily get you outside of this target window- and that can cause tracking problems.

@atmasphere 

Thanks for your reply, really appreciate it!

Any one own a Hi-Fi News test record can easily determine how significant that loading resistance affect the cantilever to be stiffer and introducing possible tracking issues, just play with the loading resistance setting and run the cartridge/arm resonance test.

If you doubt this I recommend a simple test, which is to run a square wave through the cartridge itself and observe the results on an oscilloscope. If the square wave rings, then loading will affect it at audio frequencies. If you do this with any LOMC cartridge you'll see that the inductance of the cartridge is so low that a square wave at any audio frequency will look perfect on the oscilloscope. So its obvious then that the loading isn't affecting the tonality of the cartridge. Something else is.

I don't have any record with square wave test track on hand, can you recommend one?

@rauliruegas

Perform a simple test with Hi-Fi News test record will give us the answer, do you agree?

The obvious difference between the Zestos and PS Audio as loading changes is clear as a bell.

@fundsgon 

It only confirmed the Zestos is sensitive to RFI and PS Audio stellar is not.

Can you do a cartridge/arm resonance test for 100Ω and 47kΩ loading and see if the resonance frequency changed significantly?

Thanks

Perhaps I'd have a different result with a different phono cartridge.

We have a loading strip on our preamps too, and I advise customers with LOMC cartridges to not use it. But if you have a higher output cartridge, the loading strip can be quite handy! Because of their higher inductance, high output cartridges have that electrical peak at a lower frequency, which can be at the high end of the audio band or just outside of it. The winding of a higher output cartridge tends to have a lower Q value so loading can be helpful to reduce ringing. 

@cleeds 

That's what I thought, and thanks to atmasphere confirmed it.

ARC and ML (No. 32) not only provide a range of loading resistance settings, they even have "custom Loading" option for user to fine tune their setting!

@rauliruegas 

Thanks for your test LP recommendations, I will look it up.

BTW, I already have Hi-Fi News Test LP- The Producer's Cut  and The Ultimate Analog Test LP by Analog Productions.

@rauliruegas

Sorry for the late reply, I’ve been busy with my accountant try to file tax return by next Monday.

I did the Hi-Fi News resonance test on a Denon DL-103 and set the loading at 100Ω and 47kΩ, seems like both loadings unsusceptible to the resonant frequency.

@holmz 

I always prefer phono stage featured user select-able loading option, so the user can choose their preference.

And did you choose 100 ohms, 47 kph, or something in between?

@holmz

Sorry for the late reply, finally get the tax return filed! 😌

For the Denon DL-103, I chose 1kΩ, because I don’t want to use a too low resistive load to load down the cartridge and at the same time don’t want to use a higher resistance to eliminate those unwanted RFI get into the phono input.

IMO, since RFI is not the music contents, why not apply a correct amount of resistive load to damp the unwanted RFI even though the phono stage can handle it.

http://www.hagtech.com/loading.html

@wynpalmer4

👍 Thanks! It's always a pleasure to read your posting in here, AK and diyaudio!🙏