When I wrote about my memories of the strain gauge cartridge it was presented as mere ramblings. Since that post, there's been a swirl of controversy and questions. Who knew?
One question, in particular, revolved around the cartridge's supposed disregard for the need of the RIAA curve. Several among you, including my friend Richard Murrison, questioned the pat explanation as presented on the internet by (among others) Soundsmith, the company that currently manufactures a strain gauge cartridge (which I understand sounds exceptional).
Out of the woodwork comes my friend, engineer Gary Gallo. Gary wrote the following which I share with you here:
Back in 2016 I wrote an article for Linear Audio on RIAA EQ for Displacement-Sensitive phono cartridges. What prompted this investigation was Soundsmith’s claims for their strain-gauge cartridges, and their explanation of RIAA EQ, which is simply incorrect. Peter Lederman refused to answer my questions about how his cartridges could maintain flat response in the constant-velocity portions of the RIAA curve – I made three attempts to get an answer out of him, but he cut off correspondence with me.
You’ll note that DS Audio, manufacturer of LED cartridges that are also displacement-sensitive, holds the same views as me on RIAA EQ. I quote a letter from their chief engineer in my article.
In 2018 I gave presentation for the Connecticut Audio Society on this subject, and took things a bit further than the article. Strain-gauge cartridges use piezo-resistive semiconductors, and I think a piezo-resistive semiconductor’s internal capacitance, interacting with the load, is probably why the constant-velocity portions of the curve flatten out. I repeated that presentation for the New York chapter of the Association for Recorded Sound Collections later that year. Suffice to say, ANY phono cartridge claiming to be displacement sensitive, that outputs a flat response without any RIAA equalization, isn’t truly displacement sensitive. The old Panasonic strain-gauge cartridges certainly weren’t, and I think my simulations on their EQ circuit demonstrate that. That EQ circuit, as you’ll see, compensated for several anomalies in the cartridges response.
As they say on those cable TV ads, “Wait…There’s more!”
The presentation I gave for the NY ARSC Chapter can be seen on their YouTube channel:
Linear Audio ceased publication a few years back. All back issues are now available in electronic form, along with the printed volumes:
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