Cartridge Loading- Low output M/C

Wynpalmer4 5-25-2018
Contrary to what has been said, for LOMC the capacitance, unless it is quite large (in the order of .1uF), is essentially irrelevant ....

As explained earlier by me, and by Atmasphere (Ralph Karsten of Atma-Sphere Music Systems), and in the statement I quoted by Jonathan Carr (Lyra cartridge designer), while load capacitance is indeed essentially irrelevant to the cartridge, it is not irrelevant to phono stages whose design is such that RF frequencies received at their inputs can have audible consequences.

Regards,
-- Al

I may not be a renowned Audio Designer, but I am a somewhat renowned IC designer with credits that include cell phone transceivers and high performance opamps. 
In truth, the issue with phono stage RF has little to do with the capacitance loading- rather it's that many RIAA stages are designed to be non-inverting and lack the additional pole necessary to provide attenuation at ultrasonic frequencies and above. For example:
http://audiokarma.org/forums/index.php?threads/ad797-phono-stage-build-and-help-desk-thread.501186/p...
Where I discuss this very problem as an aside to optimizing an opamp based phono stage.
The non-inverting amplifiers used in an RIAA stage never have a gain below unity unless an additional pole is added. It's hard to see why adding a capacitance of significant value to the input of a phono stage helps when the self resonant frequency of most larger value caps is well below the RF region of interest. Indeed, if that is your concern, then adding several caps of scaled value 1-2 orders of magnitude apart, say 0.1uF//3300pF//100pF as the cartridge load would be the way to go, and who does that- except as an extra pole in a non-inverting RIAA stage.
I'm a believer in fixing the problem where it exists and not by adding an additional parameter to an already over-constrained problem.

I have my Nova II phono pre capacitance set at 100pF for my Delos and I use an AQ Cougar phono cable with total cap at 60pF. Lyra suggests using the lowest cap cable you can, and for me it does make a difference, as I was using a very high cap cable in the 350pF range with loading at 121 ohms.
The dynamics and resolution is so much better now.

Just for interest sake, I ran some simulations with an "ideal" MC cartridge with a 5mH/5 ohms coil in conjunction with a near ideal active RIAA design with non inverting amps and the extra pole.

The ideal load- the one that results in the closest compliance to RIAA
is with 22nF||110 ohms (+/-.06dB 20Hz-20kHz). It also has 50dB of attenuation (relative to the ideal RIAA stage) at 1MHZ and 95dB at 10MHz. Dropping the load R to 100 ohms reduces the 20kHz output by 0.2dB. 
Increasing the capacitance to 0.1uf and reducing the load to 68ohms is almost as good as this.
None of these simulations include the mechanical response.
Anyway- as can be seen there is no perfect answer. There are many combinations of load R/C that are pretty well equivalent and you can't even simulate or calculate it to find a decent answer as no MC cartridge maker that I am aware of provides even simple models for their device, even when asked.

Unfortunately accentuated dynamics and resolution all too often mean a really nasty peak at the HF. In my experience, getting a good test record and testing the RIAA response can be a real eye opener.
Most of the differences in response that occur due to changes in load are in the 10k-20kHz range.