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What can you tell me about toroidal pickups, like the ones on '70s Ovation Breadwinner guitars?

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  • What can you tell me about toroidal pickups, like the ones on '70s Ovation Breadwinner guitars?

    Can't find any useful pics or videos on them. How is a "toroidal" winding different?

  • #2
    Just from quick looking, I think they were paired with a pre-amp, so they were probably low-Z designs. Hard to believe the coil would actually be a toroid, because a toroid confines most of the magnetic field in the toroid core, but with a guitar pickup the idea is to involve the guitar string into the magnetic field, and not to keep it out.

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    • #3
      Originally posted by Mark Hammer View Post
      Can't find any useful pics or videos on them. How is a "toroidal" winding different?
      I always take Wikipedia with a grain (or a bucket) of salt.
      Being written by "we the People" meaning "anybody", it often contains unbased statements by no clue people.
      Or best case, poorly written.

      I see nothing "toroidal" here, but it might be poor wording to describe a roughly oval winding, think lipstick or "gold leaf" pickups, where a coil is wound around a round core (hint: cheap, easy and ultrafast)which "looks" like a toroid, sort of, paper taped around and then squeezed into an oval-ish shape, then 2 or 3 button or a single bar ceramic are placed inside that coil.




      This is the Ovation pickup

      Click image for larger version  Name:	vintage-1973-Ovation-Breadwinner-Deacon-Single-Coil-Neck.jpg Views:	0 Size:	28.0 KB ID:	950899

      I think it might contain an upward pointing C shape piece of iron, one edge tapped for screws, the other ending in those rectangular thingies, and magnet and coil hidden inside the cover.

      That, stretching imagination as far as possible, trying to fit both picture and "description".

      In a nutshell: in a conventional toroid, the word describes the magnetic core, here it seems to describe an (unseen) bobbin.

      More, clear as mud

      Click image for larger version  Name:	krebal08uoj6jqa29xp5.jpg Views:	0 Size:	115.7 KB ID:	950900

      We might have a rectangular ceramic bar, with, say, North towards "saddle rectangles", South towards screw block, and maybe a "toroidal bobbin" wound or slipped around it.
      Last edited by J M Fahey; 01-28-2022, 01:07 AM.
      Juan Manuel Fahey

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      • #4
        Yeah, the screws being so close to the edge, it definitely reminds me of those old fake humbuckers with a cheapo single coil underneath. There's virtually no way those rectangles could be involved with coils, since they abut the edge of the pickup.

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        • #5
          The one useful Youtube I've seen demonstrating the native sound of the pickups (i.e., NOT pushing an amp into coloration of any kind) really does sound like a low-impedance pickup, given the clarity. The presence of a transformer on the guitar-electronics circuit board reinforces that view. And that, in turn, is supplemented by the fact that they were released a little after the Les Paul Recording model hit the market.

          As for what lies underneath the cover, compared to what the cover suggests, I learned that lesson long ago, taking apart an Epiphone New Yorker pickup, a gold foil, and a 1948 DeArmond. The New Yorker and gold foil both have a row of screws that suggests a 2nd coil, but are simply there to provide adjustment of the C-shaped field of the one coil sitting in the middle.

          My reason for originally asking is that I'd never heard any other pickup referred to as having "toroidal coil" pickups. I'm vaguely familiar with toroidal power transformers, and thought "How on earth would you do that with a pickup?".

          BTW, is that picture of the coil and magnet looking towards the baseplate, or looking "up" from the baseplate?

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          • #6
            Originally posted by Mark Hammer View Post
            The one useful Youtube I've seen demonstrating the native sound of the pickups (i.e., NOT pushing an amp into coloration of any kind) really does sound like a low-impedance pickup, given the clarity. The presence of a transformer on the guitar-electronics circuit board reinforces that view. And that, in turn, is supplemented by the fact that they were released a little after the Les Paul Recording model hit the market.

            As for what lies underneath the cover, compared to what the cover suggests, I learned that lesson long ago, taking apart an Epiphone New Yorker pickup, a gold foil, and a 1948 DeArmond. The New Yorker and gold foil both have a row of screws that suggests a 2nd coil, but are simply there to provide adjustment of the C-shaped field of the one coil sitting in the middle.

            My reason for originally asking is that I'd never heard any other pickup referred to as having "toroidal coil" pickups. I'm vaguely familiar with toroidal power transformers, and thought "How on earth would you do that with a pickup?".

            BTW, is that picture of the coil and magnet looking towards the baseplate, or looking "up" from the baseplate?
            Mark,

            The pickup described below has a “toroidal coil”.

            You can use a small toroid current transformer with 500, 1000 turns for a low impedance output up to one with about 5000 turns for a higher impedance output. All you need to do is run a single loop of very thick copper wire from AWG8 to AWG4 and form a string loop with a very low resistance connection with the magnet or magnets in the center. Since thicker solid copper wire has a skin effect in the audible mid frequency range, you can hear a difference in tonal output. Fine stranded wire of fine wire bundles are easier to work with but require careful attention to getting the lowest resistance connection to maximize the output.

            One benefit of this design is that you do not need to cut out the wood under the strings to place the pickup in. The only cutout is about a cubic inch to place the current transformer in, but not under the string path, with the copper wire loop and magnet laying on the guitar top with a thickness less than the fingerboard height above the body.

            My best experiments use a Triad CSE-186L with the three turns of the installed primary removed leaving about a .125 inch opening to accommodate an AWG8 copper wire string loop. Just place a thin layer of tape on the metal transformer metal frame to prevent the string loop from contacting the metal frame. Lowest noise comes from using the CSE-186L metal frame as a ground and the string loop as part of the common ground. Use the two current transformer output leads as pins 2 and 3 of an XLR input with pin 1 being the common ground.

            One advantage of having a low impedance output is that cable capacitance has less of an audible impact on the pickup tone.

            I hope this gives you another pickup design to think about.

            Joseph J. Rogowski

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