Cartridge Loading- Low output M/C

There is a tremendous amount of info here, both super technical as well as the basics. If you do one thing, that is click on the link JCarr posted from 4yrs ago on Whatsbestforum, it gets you well into cartridge loading topic by an expert.
I read that article 3yrs ago and that opened my eyes to LOMC loading, and what is happening from stylus thru phono stage to power amp...and why.

It is very true, we must use our ears and chose what sounds best for us, even in the Lyra instruction booklet it gives you the mathematical process but then also states, or determine by listening.

The one thing for sure is that I will never own a phono stage that only gives me a couple loading options as well as no gain settings (more gain is not the answer).
And yes I do want to enjoy the music, more than anything, but I want that at the highest level of resolution and dynamics I can afford or adjust for.

Cheers,

Well, if the simulations are to be believed the results are quite interesting, if hardly entirely unexpected.
I'm simulating an opamp based phono stage with near perfect 20-20kHz RIAA compliance, with both active FB and passive RIAA implementations. The feedback design has the extra HF pole.
 If you load the cartridge with 47k the input rings at the resonant frequency of the input network (>4MHz) when you hit the RIAA preemphasis network with a 2KHz square wave and it lasts for 10s of us. 
When the load is reduced to 1k the ringing is damped and it ends in a few us. 
Into 100 ohms the response is well damped with a small over shoot and after 1us it tracks the input perfectly. At 400 ohms there is just a small amount of ringing.
Adding 0.1uF to the 100ohm load noticeably slows the edge of the feedback RIAA preamp output square wave compared to 85pF. Increasing the R to 400 ohms, and keeping the 85pF shows the slight ringing on the output response but doesn't have a reduced rise time, increasing the R to 47k shows significant near-oscillation at the output of the preamp.
The passive design shows none of these pathologies with the change in load R, and always has a significantly slower and essentially constant, risetime, so clearly the RIAA de-emphasis producing opamps are reacting to the HF signal.
So, perhaps the answer to the loading question is, no matter how unlikely it seems- it depends on the architecture of your phono amplifer!

Great info, Wyn; thanks! And thanks also to Catcher10 for his inputs.

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

This is exactly what Ralph (Atmasphere) has said in more than a few prior threads here, as well as in this one, that optimal loading is primarily dependent on the design of the phono stage.

BTW, the Herron phono stage I own, which as I previously mentioned I (and also some other members here) run with essentially no resistive load whatsoever (just the input resistance of a FET stage, which is nearly infinite) uses passive RIAA equalization. As do the phono stages that are built into Ralph’s preamps.

Thanks again. Best regards,
-- Al

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!

catcher10 (and other experts here)
In absolute terms, does a Phono pre with multiple gain/loading options only sound it's absolute best at 1 permutation of settings?
I ask because I once read a ARC Ref 2 Phono review and it was said that it sounded better at the lower gain setting. Then in my pre (an older ARC Ref) the loading involves soldering resistors onto some taps. To my ears this always sounds more veiled than without the resistors with the 5 carts of different recommended loadings that I have owned.