Question about Cartridge Loading

No. Loading is inversely related to the R value. The higher the R, the lower is the load on the cartridge. For an MC cartridge, the rule of thumb is to choose a load resistor value that is 10 times the internal resistance of your cartridge. If you don’t know the internal R of your cartridge, you can look it up on line. For a low output MC cartridge (LOMC), the typical internal resistance value will be anywhere from 2 to 20 ohms. A typical LOMC cartridge with a 10-ohm internal resistance will be properly loaded by a 100 ohm resistance OR HIGHER. There is no real rule for what value might sound best. Thus you may read that some like to load their LOMC cartridges at 47K ohms, which is the standard load for a Moving Magnet (MM) type cartridge but also works fine for MC. You will also read that this or that person swears by some other value in between 100 and 47K. Take it or leave it. You don’t want to go below 10 times the internal resistance for two reasons: (1) As you go below 100 ohms for our hypothetical LOMC, you will gradually be losing more and more signal voltage to ground. This reduces the usable gain of the cartridge, and (2) likewise, lowering the load R below 100 ohms will also cause a high frequency roll-off that dulls the sound of the cartridge. Again, that is a gradual phenomenon that gets more and more apparent as the load R approaches the internal R of the cartridge. This is a simple explanation. I hope it helps.

@lewm 

Thanks for your explanation.

I know I should play around between the different load values to see what sounds best in my system (I find it hard as the differences are probably subtle and hard to detect, at least for me).

Dear @jay73  : LOMC cartridge is not sensitive to load impedance always that the load impedance does not be the same value of the internal cartridge resistance.

If your phono stage is an active ( not SUT. ) high gain item then will came with load impedance choicesd and you can test/play with all of them and through those tests you will deciode which load impedance value even your needs. and that's it.

Regards and enjoy the MUSIC MNOT DISTORTIONS,

R.

Cartridge Loading

Dear @hagtech  : Yes your link/calculator is really great. I wish that the LOMC cartridge manufacturers includes the cartridge inductance in its specs that's need it in your calculator.

R.

For LOMC cartridges, where the typical inductance is less than 50 micro-Henries, and often much less than that, does it really matter much to include inductance in the calculation?  I doubt it.  We saw a month ago that for the low output MI cartridges like Sussuro, which has an internal R of only 10 ohms, inductance surely does matter, because it's about 1000X higher than for a typical LOMC.

My Pure Fidelity Stratos (based on the Gold Note Donatello) has a 45 ohm impedance and recommends loading between 400-500 ohm (figuring 450 ohm to be optimal?). However I haven’t really heard any difference between 100 ohm and any variation between 400-500 ohm. 

What I did on my JC3+ phono stage was set the variable dials to 450 ohm and then flipped the switches between MC Variable and MC 47K and that’s where I actually noticed an improvement. At 47K the soundstage is wider and deeper with no detrimental effects that I can hear on top end, harshness, or bass, so that is what I’m sticking with. 

I am guessing a lot of this must be system-dependent because according to the manufacturer I should get optimal sound between 400-500 ohm but according to my ears I can’t hear any differences or improvements until I load it all the way at 47K. 

It's not that 450 ohms is "optimal".  It's that you want the phono stage input impedance to be at least 10X the internal impedance of the cartridge.  In your case, 10X = 450 ohms.  So any input impedance equal to OR GREATER THAN 450 ohms would comply with the conventional wisdom.  If you don't hear a difference between 100R and 450R, I suggest you try 1000R or even 47K.  Also, check the VTA for your cartridge.  If the tonearm is not level with the LP surface, is the pivot lower than the headshell?  That can cause loss of HF response.  Also check for any number of other things that can affect HF response.

Dear @lewm  : The OP cartridge was reviewed and the reviewer said performs just fine at 100 ohms that's is way out of your 10X rule. In reality it's not a rule because I experienced several cartridges below that with very good listen sessions.  

Btw, "  does it really matter much to include inductance in the calculation?  I doubt it. "  Do you already make your job using Hagermann calculator at least with 6-7 different examples?  if not then maybe time for you can do it and confirm that " doubt " you are talking about. Don't you think?

R.

Raul, It’s not my rule. It’s just physics. If you load a cartridge that has a 45R internal impedance with a 100R resistor, of course it will work. But a large fraction of the cartridge voltage output will be lost to ground and you will lose some HF bandwidth. These two numbers can be precisely calculated but the end result is more complex because of frequency dependency. If the net result sounds best, I am not about to quibble, but if a novice asks me a question about loading, I feel obliged to tell it like it is. Then let the other guy decide for himself.

As to the importance of inductance in the Hegerman calculator for LOMC cartridges.  Did you add in say 10-20 microHenries for an LOMC, or whatever is the value for any particular LOMC?  And does it make a difference?  Of course it will perturb the value a bit, but not by any important amount.  Tell me what you found out.

Jay, I always use the cartridge manufacturer's suggestion and stick with it but, my phono stage requires removing the bottom and soldering in resistors to change the load. Just use what you think sounds best to you. It is your system and your ears. 

With experience you will know what you want to hear. When you are not sure you tend to second guess yourself. As an audiophile you owe it to yourself to listen to as many systems as you can at dealers and shows to get an idea of what systems can do. You'll have to dweedle through a bunch of bad systems but when you hear a good one you will know it for sure. If you want to get first rate service at a high end store just drive up in a 911. A Yellow one works best:-)

Coil inductance has biggest impact for cartridge loading if its inductance is higher than 1mH.

If you want to use a LOMC cartridge, avoid phono stage that only provide 100Ω fixed loading resistance for MC cartridge.

If you have a LOMC cartridge, you'll find that loading has little effect on its audible bandwidth. However it can have an enourmous effect on the phono section being driven by the cartridge, if the phono section is sensitive to RFI being injected at its input.

Above @hagtech kindly posted a link to his calculator. If you drop the inductance value of your cartridge into it, and then the capacitance of your phono cable in too (a typical phono cable is about 20pf/foot, FWIW), the calculator will show you the resonant frequency. With LOMC cartridges this is often in the MHz region- definitely Radio Frequencies.

That peak can be set into what is called 'excitation' in radio parlance, caused by the operation of the cartridge. This results in RFI injected into the input of the preamp, and many preamps don't deal with that very well (for example they might sound bright; you might also get more ticks and pops if the preamp has a poor high frequency overload margin). The loading resistor serves to detune that resonance, thus eliminating the RFI.

If your preamp can deal with the RFI then you'll find the loading resistor has little or no effect.

@lewm  : " cartridge was reviewed and the reviewer said performs just fine at 100 ohms that's is way out of your 10X rule. "

" lose some HF bandwidth.."  how much.Example?

Normally SPL goes a little lower.

R.

@lewm  : You don't posted then that could means you do not make your work yet  changing inductance values to looks its critical issue ( as @imhififan posted. ). Here we go with examples using HC and know the cartridge bandwindth:

L 0.5mH  and R 100 ohms  : 31.8 khz

L 0.4mH same R:  39.8 khz

L 0.1mH same R: 159.2  other example changing the R:

L 0.5mH  R 47k  :  14.9 khz. From 32 khz goes down 15 khz.

That calculator is a very good tool. Don't you think?

R.

That calculator is a very good tool. Don't you think?

Yes. Make sure that you don't confuse milliHenrys (mH) with microHenrys (uH)!

1mH is equal to 1000uH

So if you dropped 0.500mH into the calculator when it should have been 0.005mH, you'll get a bit of an error.