What innovative, unconventional cartridge designs can you recommend?

@richardbrand After reading your reply to "rauliruegas" I can only see a person enjoying their Audio Interest and had experiences.

Also I am unable to not form the view, the interest shown is from somebody having a roll of the dice on their next move for enabling a Vinyl Replay to occur in their system. The dice are rolled and the conviction shown for the decision is not based on hard evidence, it is bias based. The evidence about Photocells being non-Linear is not limited it is wide spread.

To assist and keep the noticeable dismissing my own thoughts and the description supplied by a friend out of the discussion, the following is from a individual who has a substantial experience with Photocell / non-Linear design and a AI interpretation of that description. 

Not My Words - Nor My Friends: " In general, circuit functions with non-linear behaviour don’t have linearity properties! Which for designers striving for accuracy are navigating a world with craziness.
 We humans have not come up with a general-purpose method to exactly solve non-linear equations for supporting circuits?
Each case being unique, requires a new type of circuit, requires mathematical techniques specific to theness that must undergo constant changes.
This endless approximating tends to drive everyone crazy when met with the challenge.
The usual approach to nonlinear circuits, is to bend over backwards to make it seem linear over at least some small range of operation. 

AI Interpretation:  The provided text highlights the extreme challenges engineers face when dealing with non-linear circuits, noting that these systems lack straightforward linearity properties, requiring specialized mathematical techniques for each unique case. Because non-linear elements—such as photocells, diodes, or transistors—do not have consistent, proportional responses, they create unpredictable outcomes that make achieving high accuracy difficult. 

There is no point burying ones head in the sand, the typical shown attitude shown on the Gon being " Contempt Prior to Investigation " does not cut it, there is numerous avenues to be selected that all end up at the Photocell being non-Linear. 

@richardbrand stated " any Equalizer can be used with any cartridge. "

@pindac stated " to have any real chance of being Optimised for processing the sent signal and later reverse RIAA requires a custom matched energiser for each Cartridges Photosensors used "

I can't see anything from @pindac that suggests an energizer/equaliser from any Brand is a failure when it comes to creating a replay of Vinyl Embedded Data. The actual fact pointed out is that to have this Vinyl Embedded Data optimised, the energizer/equaliser, is needing to be Custom Produced for each Cartridge, but but definitely not a ubiquitous design for all Cartridges, each design will be bespoke to each Cartridge, to produce the correct reverse RIAA.

I know on the Gon there are users of Cart's designed to work with Electro Magnetic Inductance that publicly state the noise value ranging in the 0.0?uv are the standard, noise value of 0.1 - 0.5uv are not well spoken off.  Phonostages are able to meet all of these 'uv' values consistently. A energizer/equalizer will not be consistent as the Photocells non-Linear state will prevent consistency being calculated, unless custom design is produced.

I have been fortunate to have been demonstrated a Custom Wound SUT for a particular Cartridge, also nearly all my audio equipment is custom design / built, so Custom Produced in my world is not such a big deal.

Where using my choice of Cartridge wins through is that it is a design that is Linear, with 50ish years of very high quality R&D behind it. This history results in 'off the shelf' designs or a Custom Produced SUT > Head Amp > Phonostage proving being ubiquitous for all Cartridge Models produced and used with them.      

@pindac 

each design will be bespoke to each Cartridge, to produce the correct reverse RIAA

I don't think you actually mean "each Cartridge"? 

Maybe you really mean "each Cartridge Model"?

Since all DS Audio's current Cartridge Models use the same LED and photo-electric sensors. that implies that "all current DS Audio Cartridges" only need one 'custom' design of Equalizer.  Fortunately. there are more than a score of these so-called 'custom' designs presently on the market. 

Since the circuit schematic has been placed in the public domain by DS Audio, I think we should immediately drop the word 'custom'.  We don't use it for phono stages.

I note that one of the Equalizers you favour does not even include RIAA equalisation.

The SoulNote Equalizer one model up from mine supports dozens of emphasis curves to support a plethora of records cut by record companies before RIAA became the standard.

As far as your unsubstantiated allegation that photo-receptors are non-linear (you use transistors as an example of non-linearity) you have to understand what is being varied to get a response. 

With DS Audio, what varies is only the fraction of the area of the photo-receptor exposed to the same frequency and intensity of infra-red light.  It varies from a little bit to a lot more, but unlike a transistor it does not cross a null point.  What comes out is current in direct proportion to the exposed area.  If you like, it responds in a linear fashion like a transistor biased in a pure Class A amplifier. 

I am pretty sure I have given you a reference which includes graphs, though it is the distance between the multiple lines that has to be the same for linearity.  Straight line graphs are so boring, there is no point publishing one.

@audphile1 

You described what I am hearing better than I ever could.  Thank you.

As it happened, the first record I played was an Original Master Recording of Adrian Boult conducting Elgar's transcription of a Bach organ work.  MoFi is on the cover.

Next was a direct-to-disk-master of two Beethoven piano sonatas. Like most audiophile recordings, this did not do much for me with Moving Magnet, but when the optical cartridge bit deep into the guts of the piano - transformative.

I had to play my 60-year old copy of Bruno Walter playing Mahler 9.  It came up like new.  Even the used Boult recordings (in quadrasonic sound) of the Elgar symphonies came up a treat.

The other DS Audio component I own is getting a work-out too.  The gel stylus cleaner.

@richardbrand you will be rediscovering your entire collection now. And the sound will only get better as the cartridge breaks in. I noticed with the Hana the first signs of improvement at around 30hr mark. But it really blossomed at close to 100hrs. 

Thanks for the music recommendation! I will have to listen to that Adrian Boult album on streaming if it’s available. Might get an LP later. 

Is this the record?