Practicality of reversing frequency response curve of phono cartridge / stylus

Burning question regarding phono cartridges and wondering how much this has been explored: 

How practical would it be to measure a phono cartridge's frequency response with a test record and then correct it with a digital signal processor to be ruler-flat, much like Genelec's GLM system does with a room? Does anyone offer a product that would do this? It seems that rather than spend thousands on a fancy cartridge, one could get by with an average cartridge and correct it with some rather simple processing (?)

My future plans are to use a CEDAR Cambridge processing system to archive the best examples I can find of early jazz music, and I'm forced by the nature of the records and the cartridges available to use a Shure V-15 VX with aftermarket 78-specific stylii, so I'm thinking it might be possible to correct for some of the imperfections of the cartridge if I have a baseline.



You could use DSP for your record curve ( which you need to adjust to a number of settings for old mono and 78 anyway ) and then tweak eq to suit yourself based on some test record recording passes. 


Get a good mic preamp that you can load at 47k -100k with say 30-50db gain into ADC into DAW with EQ and hit record :)


Seems like there could be better MM that could be fitted with a 78 stylus.


VERY EASY! I have all the equipment now to do that. It would be the frequency response of the cartridge/ tonearm/ Phonostage and I would need to get a test record with a sine sweep, but correcting it is easy. I can change frequency response at 1 Hz intervals with a resolution of 0.1 dB.  The processor is 64 bit floating point running at 192 kHz. It also performs room control and bass management. You could also store different curves for different cartridges. The Trinnov Amethyst does all of this and I believe the Anthem STR will also but with lower resolution. Having said all that good phono cartridges are relatively flat. In comparison to speakers in rooms they could be considered dead flat. Unless you are really anal and only listen on headphones there are way more important fish to fry.

CEDAR is a pretty old technology. I remember asking people who worked with it if it was really that good. No one thought that it was and it cost about $8000 back then.  That was 25 years ago!  I would try and find a SweetVinyl unit with SVNR.  There are lots of better mono cartridges for 78 rpm than Shure these days IMO though it is nice to have the flexibility with stylus size sometimes.

Thanks, good food for thought. A lot of what CEDAR does is pretty old, but there are still some things that have yet to be matched by other products, e.g. phase correction of mono groove walls, fixing lathe errors for 100 year old recordings, some more sophisticated EQ correction, and even some of the 78-specific crackle reduction. At a glance, SweetVinyl seems good for vinyl, but shellac is a whole different animal. In my experience, any vinyl product designed without shellac in mind will either absolutely murder shellac or be totally useless.


I agree that correcting for cartridge is probably small potatoes and almost not worth considering when dealing with shellac, but I'm still curious to hear the differences. Part of the reason is also wanting to have a library of ruler-flat transfers and not someday regretting that I could have done them better. 

The Shure V15Vx is about as good as it gets for 78s. Must-haves for any cartridge include swappable stylii and cantilevers that can take at least 5 grams of tracking force. You need at minimum 6 different stylii to be able to get best results. Groove widths vary widely. 

Having said all that good phono cartridges are relatively flat.

Actually any magnetic or moving coil cartridge is known as a constant velocity device, which is to say that their output doubles with doubling the speed at which the stylus vibrates. So they have a rising 6dB/octave response. However you are correct in the response is a pretty straight line alone that 6dB/octave rise.

The RIAA curve is meant to compensate that as well as reduce high frequency noise on the LP surface. The RIAA curve has a step in it, which causes the actual equalization to be a bit of a wavy curve. This might be a bit tricky to set up in DSP.