The strain gauge

July 28, 2022
 by Paul McGowan

For some strange reason, I have been thinking about the strain gauge phono cartridge. And, here’s the weird thing. I have never heard one.

What’s interesting to me about this strange beast is how different it is from your conventional phono cartridge.

I am always fascinated by truly different.

Most phono cartridges are generators. They rely upon movement to induce a variable magnetic field which in turn generates a voltage. The movement occurs in response to the needle in the record groove. Attached to the needle/cantilever arrangement is either a small coil of wire (moving coil) or a small magnet (moving magnet). As the disc spins the needle moves and we generate a tiny electrical signal which we first amplify and then pass it through an EQ network called the RIAA curve.

A strain gauge does not generate a voltage. Instead, it disrupts either a small voltage or impedance which is then converted to what we need to play music.

Interestingly enough, strain gauges don’t work into phono preamplifiers. Instead, they require a special analog input that is more closely related to a standard analog aux in. This is because strain gauge cartridges don’t need the EQ correction normally applied through the RIAA curve.

I see that Soundsmith is offering their version of a strain gauge cartridge and input box for $10K.

Why are we going down this road in today’s post?

Beats me.

Subscribe to Paul's Posts

48 comments on “The strain gauge”

  1. I remember Peter Thomas of PMC saying at an open day that he uses a SoundSmith Strain Gauge at home.

    I use a SoundSmith MI cartridge. It sounds tremendous and output 2mV. The owner, whose name I forget, really is quite innovative.

  2. “Why are we going down this road in today’s post?”
    “Beats me.”

    Is Paul running out of topics?? 😮
    Or is PS Audio finally (vinylly) moving into cartridges?
    😉

  3. ‘Why are we going down this road?”
    It’s part of the audio reproduction story.

    Back in the late 70’s I remember having in my store, a strain gauge cartridge and arm combo from a company called Euphonic Minaconic (not sure of the spelling). It was quite small like an OM Ortofon and fitted into the end of a very slim tonearm. It came with a small silver box of electronics that connected to an aux input. It’s a long time ago but my recollection of it at the time was very detailed, fast but lacking body and warmth.
    Sorry about the immeasurable terms.

    1. I had one, bought in London, used, late 60s

      How did it sound? Ok. My whole system then was just ok so who can say?

      Why did I go for it?
      Why have I gone for every weird and wonderful novel technology; “because it might sound better.”
      And isn’t that the song of most of us?
      Optimistically disappointed.

    1. From the Soundsmith:

      The Strain Gauge cartridge is a displacement device, producing an output that is dependent and directly proportional to the amount of displacement of the stylus, NOT the velocity, like magnetic cartridges. The RIAA recording curve used to make the original master recording with a magnetic cutter head COMPENSATES for the normal cutter head velocity response and thereby results in a groove that is basically equal “displacement” for a signal that is swept from 20 Hz. to 20 Khz. Without RIAA, the “velocity” response of the magnetic cutter head would normally cut a large displacement groove for low frequencies, and less displacement as the frequency rises. Using RIAA, which LOWERS the amplitude (volume) as the frequency lowers and raises it as the frequency increases, it “COMPENSATES” for the natural displacement differences of a magnetic cutter head’s response and RESULTS in a basically equal displacement groove, for a flat, frequency swept (20 to 20K) input signal. Since normal magnetic cartridges are velocity sensitive devices (whose output is sensitive or proportional to velocity), they need the RIAA inverse filter to result in a flat playback response of a groove cut with an RIAA recording curve. However, since the Strain Gauge is a DISPLACEMENT sensitive device, it automatically produces a basically flat response from a RIAA encoded groove, which as stated above, is a basically equal displacement recorded groove.

      1. Well, if you go on reading, the same article actually explains what is going on. The RIAA curve is a complex filter and does *not* simply compensate for the velocity/displacement effect. In principle (at least it seems that way to me), it could have done, but its designers, for whatever reasons, elected not to do it that way. Soundsmith goes on to admit that their cartridge’s natural response does in fact *deviate* from the RIAA curve, but they try to walk that back by suggesting that the difference is minor, and not worth the sonic disruptions that a correcting filter would introduce. I’m not sure about that!

        Interestingly enough, apparently there is not one unique “RIAA EQ”. Different record labels back in the day used slightly different RIAA filters. There are people out there who insist that for ultimate vinyl playback fidelity, the specific RIAA EQ filter needs to be matched to the individual recording. I read about this many moons ago, but I forget the context. I think it was something to do with laser-based cartridges, which also produce a displacement-derived output.

        1. I suspect the designers of RIAA curve decided to have a flat spot in the middle for the vocals. There’s a single-pole roll-off on either side of that to normalize displacement. This also results in smaller displacement of the treble than of the bass. Otherwise the treble velocities would be very high.

  4. Interesting review from Fremer about it! Looks like (as the DS Audio concept) it’s still not a clear recommendation without disadvantages however. Rather something for a second arm.

    1. Which disadvantages concerning „sound quality“? Why not trust your own ears? Even Ed Meitner (the most famous proponent of SACD) has designed a matching input box for DS Audio’s optical cartridges! For those who like the stylus cleaning the grooves of vinyl records the best choice. I rather clean my vinyls using an US cleaning machine before starting my laser turntable from ELP Corp., Japan. Using “needle” for reading vinyl grooves is not that innovative at all and fits best the preferences of the audiophiles labeled “conventional” or “traditional” – as discussed in an earlier post.

      1. What I mean is, if such theoretically/obviously superior concepts appear, we expect a general superiority in sound quality. What should follow is, that everyone who can afford it, jumps onto this new technology.

        This didn’t happen with the laser turntable, not with the DS cartridge concept nor the strain gauge cartridge concept. They stay niche concepts because (it seems from reviews) they are not generally superior and also have (as every concept has) some disadvantages (visible within the reviews). They may be great alternatives for those with a focus on their strengths, but partly don’t even seem to have a balanced enough overall performance, that they’d be recommendable as a basic solution and not only a second alternative. That’s my perception when reading about all of those special concepts so far.

        Sure it makes most sense to try oneself (I would love to)…I now just speak of market acceptance and reviewer’s results.

        1. I guess that in the realm of audio the majority jumps onto the cheaper concepts offering the same or an acceptable sound quality – see: Walkman, Discman, MP3, etc.. When CD-players became cheaper than the medium TT the majority also accepted the harsh and unnatural sound quality of CDs. And for those appreciating the superior sound quality of good vinyl records investing in these mentioned alternative vinyl equipment was a no-go because they had already invested that much in most expensive phono-preamp, step-up transformers, cartridges, phono-cables – all this stuff incompatible now! And don’t forget: when the laser turntable initially was launched by Final Audio, US, we saw already the decline of vinyl. Why invest in a dying technology? Thus only some libraries with a museum for vinyl records invested in the laser technology in order to avoid further damage of the grooves of these vinyl records.

        2. The main issue with both the strain gauge and DS Audio optical cartridges is that they do “this and this and this” well but also seem to not be able to do “this and this” as well as say an MC cart.

          The key is everything in audio is a compromise, and it becomes a game of whether the advantages outweigh the downsides for the kind of music YOU prefer to listen to.

          The ELP laser turntable had so many issues it’s not surprising it’s never made any real dent in the industry, and for that matter even the target market of museums and archivists don’t use one, they continue to use regular turntables and cartridges.

  5. In the 1959’s Zenith used a phono cartridge in some of their radio consoles that varied the capacitance in a 10.7Mhz tank circuit and fed that into the IF circuit of the FM radio. I only worked on a few of them and I recall them being expensive and finicky. $25 was a lot of money back then when the average ceramic cartridge was going for $2-3 at the radio supply distributor. Back then almost everything used ceramic cartridges and while these FM cartridges worked they were beset by all kinds of interference that just made them impractical. I don’t think they were ever used by anyone other than Zenith.

    This article goes into some detail about how the strain gauge cartridge works –

    https://www.sound-smith.com/faq/what-so-unique-about-strain-gauge-cartridge-how-does-it-work-why-no-riaa-or-phono-preamp

    Bob

  6. Hopefully, you are going down this path to have PS Audio offer a total system; turntable, tonearm, cartridge. I think you have everything else covered, accept cables, I guess.

      1. LOL!

        Actually, I don’t see the point of an audiophile grade AM/FM tuner. I’m open to being to be corrected, but it seems to me that even the best FM broadcasts are not derived from correspondingly audiophile-grade sources.

        1. There seems to be a sub-cult of FM fanatics, Richard. I’m not one of them, but I do listen to my local NPR station that has an exceptionally good, very minimally compressed signal. I spend about 2 hours a week in that medium with a tweaked, quartz-locked FM tuner from the early 1090s. I’d tell you that it sounds almost as good as my CD playback chain, but you wouldn’t believe me. 😎

  7. If you’re going to discuss this, you should mention DS Audio’s series of optical cartridges as well.

    You can pick up a combo of cartridge and input box for less than a high end MC cartridge and phono stage.

  8. Paul, as you know, years ago there always seemed to be more discussion about strain-gauge than actual products available. Perhaps one reason was cost, both the cartridge and playback device were more expensive than the popular normal cartridges and phono stages at that time.

    Also, it was a two-step commitment. Simply buying the strain-gauge cartridge was not enough.

  9. Perhaps you are a cycling fan and watching Tour de France Femmes. Your stream of thought noticed team Le Col Wahoo, then recalled Wahoo purchased Speedplay pedals for their connected power meter technology. Then you recall that meter is based on strain gauges reporting power via Ant+ network up to the Wahoo bike computer, which made you consider a strain gauge cartridge passing audio data directly into a Sprout because the BLE runs at the same frequency as ANT+, then you considered a fully wireless, loss-less direct to amp phono set-up which cost around $10K USD, which is about the same as any bike ridden in the TdF and … we are back to bike racing…

  10. I’ve heard the Soundsmith and the Sao Win system, decades ago, and have been intrigued by both. I thought both sounded excellent, the Soundsmith at a New York audio show and the Win in HP’s system back in the day. It’s hard to describe but they seemed to get a great amount of detail and spaciousness but not in the same manner as a moving coil. I’d like to hear one again to refresh my memory.

    1. I would love to hear one as well, Frank. Back in the dear old 70s I was at CES and wandering around one of the hotels that had many of the esoteric manufacturers occupying suites, I met Sao Win and listened to his new strain gauge cartridge. He may have demonstrated it in I think, a Lenco with a straight tracking arm attached. My memory is a bit fuzzy these days. I do remember being quite impressed with the sound. I don’t recall the system it played through. I do remember that there were several small companies in the same suite to save costs and many shared each others equipment for demo purposes. Ahh, the good old days…

    2. Frank, stop by the next time you are in Murrieta / Temecula / SouthernCal! I’ll open up my still sealed copy of Say Something from Octave Records. I have two Win Labs cartridges – the original SDT-10 (bought in 1979) and an SDT-10.2 with original and upgraded decoders. I also cornered the market on Panasonic strain-gauge cartridges with three of them, 2 CD-4 decoders, & the CD-4 receiver.
      I would not be able to afford the SoundSmith cartridge at over 10 times the price I paid in 1978, but that would be a dream!

      1. Thanks for your kind offer! I’m on the East Coast and haven’t been to California since I can remember, but would love to go back someday.

        I did spend quite a bit of time in the Soundsmith room at one of the audio shows (I can’t remember because I’ve been to Peter’s rooms a few times). It really was something special. As was the cartridge with the cactus cantilever.

  11. A strain gauge?
    Isn’t a ceramic cartridge a kind of a strain gauge?
    Maybe more refined but really good ones I’ve heard are great in the demo years ago.
    Is what is old is new again?
    No phono preamp required.

    1. Exactly the same thought occurred to me. Ceramic, and the earlier crystal, cartridges were displacement rather than velocity detectors and could be fudged to give an output which was approximately without RIAA.

  12. There are a lot of clever people out there, original thinkers creating new concepts but it’s not common for those new ideas to gain universal acceptance and there’s usually a good reason. Cost is always a major consideration but on reflection the idea and results weren’t as good as first imagined.

    A typical example is the Soviet Ekranoplan, a ground effect vehicle which was brilliant in theory but drawbacks overruled it’s useability. Wiki can explain it better than me.

    https://en.m.wikipedia.org/wiki/Ground-effect_vehicle

    Smaller variants were experimented with and looked great fun, a new form of recreational transport, but the same drawbacks remained. The requirement for a smooth surface and the chance of meeting a rogue wave on a calm sea meant it might not end well.

    Thought process is always a curiosity. Martin reminded me the other day how early U.K. magazines come out, in particular the Hi-Fi News September edition is already available, in July. I always thought this faintly ridiculous and considered if this carries on we’ll soon be having Christmas in July, then remembered ‘Winter in July’ the ‘Bomb the Bass’ track. This was one of the first songs to be recorded using RSS, the Roland Sound Space technology.

    https://segaretro.org/Roland_Sound_Space#:~:text=Roland%20Sound%20Space%20(RSS)%20is,out%20of%20regular%20stereo%20speakers.

    I remember it being featured on the BBC television program ‘Tomorrow’s World’. This was originally presented by the late Raymond Baxter, a true gentleman, ex RAF and an accomplished rally driver competing many times in the Monte Carlo Rally. If you’ve got a few spare moments suggest you find some videos on YouTube where he is commentating, he did a lot of air shows and motor races, classic stuff. I used to love that program but the joke was that if something was featured on the show it was the kiss of death and it would never see the light of day again. How often that was true. Anyway RSS is another example of something that never really caught on, at least musically, and is now superseded.

    Bit of a rambling post from me today the reason being I’ve sprained my foot. I guess it provides a great opportunity for more listening time, but I’m not happy. 🙁 🙁

    1. Hi performance bass boats like those from BassCat and Allison use principles of ground effect to lift the hull out of the water leaving only the pad and prop in the water.
      The hull acts as a wing and traps a pocket of air underneath. Many Allisons will exceed 100mph.
      Catamarans at Lake of the Ozarks hit 200mph+ and are not affected by the rough water. https://marinetechnologyinc.com/

      1. They look like fun but very expensive fun. I’ve seen the racing versions on the tv and sometimes they get a bit too much air underneath and then over they go, backwards. No doubt that’s when the crew really appreciate their life jackets but clearly it’s extremely dangerous.

    2. Sorry to hear that you sprained your foot Rich.
      They are still trying to convince us to have Christmas in July down here
      …I guess because it’s winter 😉

      1. Thanks. The thing is I can’t even claim I was shifting heavy equipment around. I just got up from my seat, like you would when changing a CD, knee gave way and foot twisted over, job done. I guess everyone’s going to say now I should be streaming, because it’s safer.
        The real irony is I had a trip planned for tomorrow and I decided not to go out cycling because I didn’t want to take any unnecessary risks. Stay home and stay safe. Mmmm.

  13. Why are we going down this road in today’s post?… so we can take the long way home.

    Interesting. I am going to spend to time digesting this, that is the strange strain gauge.

  14. Dear jazznut,

    Have you had occasion to listen to a DS Audio optical cartridge in a familiar system? It is far beyond a mere “concept.” The company is in its third generation of cartridge models.

    I have listened at length to the most recent generation of DS Audio cartridges seven times across three different systems. Each of these friends, one of whom is a reviewer, has adopted a DS Audio cartridge as his primary cartridge.

    I find the transparency, detail, dynamics, resolution and low surface noise of the DS Audio optical cartridges to be amazing. The transparency, detail and resolution are achieved without any of the brightness or edginess I hear and dislike from cartridges such as the Lyra Atlas and the Ortofon Anna.

    I personally am not completely sold on the optical cartridge, however. I just can’t avoid the feeling that some smidgen of naturalness or musicality is missing. But this is an open question, not a final conclusion.

    I will be curious to hear a DS Audio optical cartridge again when the first tube decoder is released.

  15. I have often wondered how such alternative mechanisms might be used to make better microphones. My guess is that the strain gauge approach is unlikely to make a better microphone, but the optical approach might work well. One challenge might be keeping the signal-to-noise ratio high enough. Along similar lines, I have also wondered about the feasibility of making a microphone without a diaphragm (i.e., without any moving parts), similar to the “flame tweeter” from several decades ago; that would be the ideal of low moving mass, but again noise is a problem. If PS Audio ever decides to investigate building microphones, there might be a good market for that, besides contributing something extra to the Octave Records process!

    1. Haha Tony, that cheered me up.
      Funniest comment so far.
      Say what you mean. 😉
      I don’t think Paul was entirely sure either.
      Still, does everything need a point, it’s just a bit of fun.

  16. I had one of those RAM audio strain gauge cartridges in college. Wasn’t very warm, but sure lit up the leaf tweeters! Interface box finally broke and that was the end of it

  17. I accept that we live in a world that, at the moment, is deeply polarized. What I do not accept is that so many adopt their deeply polarized viewpoints on the slimmest slices of data and happily reject viewpoints that run counter to theirs. Maybe it is because it’s just easier to do so. One less thing to have to enter into the already-complicated calculus of how to view the world. I don’t know.

    What I do know is that this thread seems to contain very few, if any, comments from those who have actually heard not just “a” strain gauge, but, what in my opinion, is the leading version of one, the Soundsmith, designed by Peter Ledermann. Full disclosure, I have happily used the Soundsmith SG-600 (not the entry-level SG-200) for the better part of a decade and, despite regular opportunities to expand my slim data set (I will, for example, be auditioning the Esoteric phono pre mated to a Kiseki Purpleheart this week), have heard nothing to tempt me to switch gear. I find the cartridge and dedicated preamp to be one of the most revealing, full-bodied, and tonally accurate phono reproduction systems I have ever heard. Its ability to resolve the analog signal is exceptional. But, as with everyone in this hobby, it’s not worth trusting an enthusiast.

    Instead, I encourage you to, when you have the chance, listen. And, shame on you, Paul. Peter Ledermann dutifully showed up to RMAF every year, while it was operating (sob) and, in any one of those, you could have heard his system, sounding so much better than it had any right to do, playing through a pair of diminutive bookshelf speakers. But in the absence of this, anyone who enjoys analog playback should take the time to check out one of the many YouTube videos of Ledermann, such as this one from RMAF 2018:

    https://www.youtube.com/watch?v=WmwnN_T_wW8

    Not only has he designed the Strain Gauge and a raft of more traditional and highly-regarded cartridges, but is one of only a FEW cartridge rebuilders in the world, who does not simply replace stylus and cantilever in a retip job, but rebuilds the entire motor structure. If you can stand the endless wait to get him on your job, he is one of only a few technicians in the world that well-informed analogaholics will trust with their cartridges.

    I also saw that someone on the thread had characterized M. Fremer’s Stereophile review of the SG-200 in this way: “it’s still not a clear recommendation without disadvantages however.” Here is what I read from that review’s conclusion:

    “Adherents of strain-gauge cartridges warned me that, once I’d heard one in my system, I would become hopelessly addicted to it. After spending a few months listening to the Soundsmith Strain Gauge SG-200, and despite the obvious need to pick apart its sonic character for this review, I’ve found that they were right. The SG-200 is a unique game-changing product … If I could afford it right now, I’d buy the SG-200 in a Peekskill minute. It’s as addicting as its proponents say, and I’m going to miss it.”

    And a final note: the Soundsmith Strain Gauge is a precision device. Setup must be equally precise. It is in no way forgiving of careless or cursory setup.

Leave a Reply

Stop by for a tour:
Mon-Fri, 8:30am-5pm MST

4865 Sterling Dr.
Boulder, CO 80301
1-800-PSAUDIO

Join the hi-fi family

Stop by for a tour:
4865 Sterling Dr.
Boulder, CO 80301

Join the hi-fi family

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram