Pickups for bronze wound strings

[fieldwrangler]

Folks -

I need to make one of these things and, as usual, I first look at what everyone else has done.

Most of the existing (and historic) units have their designs loosely on display but there are two that have me wondering if anyone's poked under their hoods.

One is the original Barcus-Berry mag. Actually there seem to be two versions of this, one with a pickup coil & a dummy and the other a conventional side-by-side thin humbucker. However, it does seem that they may have in fact done something specific with the magnetics on these things.

The other is the pickups that Fishman Transducer manufactures (from a Mike VanDen design, i believe) under the "Rare Earth" heading.

In addition, if anyone's made something for this application that they were happy with (and can share some non-proprietry advice) I'd be most appreciative.

Bob Palmieri

[Steve Conner]

I once put a couple of bronze wound strings on my electric guitar in an emergency. They worked, and didn't sound much different to the other ones: maybe a bit weaker.

The wrapping might be bronze, but the core is still steel.

[fieldwrangler]

Steve -

Yup; I think for the most part delivering a balanced output just means an exaggerated version of familiar staggering strategies and such.

Tone is, as usual, a largely subjective issue.

Bob Palmieri

[Sweetfinger]

As stated above, Bronze or Brass strings still have a steel core. Since the (presumed) goal in an acoustic pickup is not distortion or drive, most acoustic pickups are designed for a clean, articulate sound- and are usually low wind designs and the design or stagger(if any) is aimed at getting a good even response from all strings. You could look back at early Dearmond designs to see how they handled it. Some pickups had a separate coil for the unwound strings. A few have a drastically weaker magnet for the "B" string or even no magnet directly underneath like the neck pickup for the Taylor Expression system.

[bbsailor]

As stated above, Bronze or Brass strings still have a steel core. Since the (presumed) goal in an acoustic pickup is not distortion or drive, most acoustic pickups are designed for a clean, articulate sound- and are usually low wind designs and the design or stagger(if any) is aimed at getting a good even response from all strings. You could look back at early Dearmond designs to see how they handled it. Some pickups had a separate coil for the unwound strings. A few have a drastically weaker magnet for the "B" string or even no magnet directly underneath like the neck pickup for the Taylor Expression system.

Sweetfinger,

I measured my Lace California acoustic pickup and it pretty much matches what you said (about 4K DCR; 4600 Hz resonance; 1.3H inductance). Here are some more details. Moving a small screwdriver sideways over the top of the pickup shows a clear difference in magnetic strength with the bass strings being stronger than the treble strings magnetic field. I connected the pickup to my oscilloscope with a 1M ohm input impedance and obtained the following results when plucking the two E strings string lightly as I would do using a clamp-on guitar tuner. The bass E string: 50 millivolts P-P; treble E string: 20 millivolts P-P. I mounted an Alumitone (strat type) in one of my acoustic guitars and had to lower the treble side down about .25" lower than the bass side to get a more balanced sound.

The California acoustic pickup is pretty quiet. Some other acoustic pickups I have tried have a higher output and and produce noise when the strings are not touched with the hand. The solution, in this case, is to use one of the Stewart McDonald Platemates, a brass plate that fits under the guitar top with "keyhole" type holes that keep the ball end of the string from digging into the wood plate under the guitar top. They come in three string pin spacings to fit most guitars. Just solder a ground wire to this brass plate and connect it to the pickup ground wire to quiet the noise.

Thanks for your good observations about acoustic pickups.

Joseph Rogowski

[FunkyKikuchiyo]

I've had plenty of experiences with tranducers wherein I have to come up with a lot of tricks to keep the B under control and the G somewhat audible. The times I've seen someone put a regular electric guitar pickup into an acoustic (bad idea) it has sounded absolutely dreadful, even if it is staggered. I'd had the differing magnet idea... glad to know someone beat me to it! heh.

Just out of curiosity, are you folks testing your pickup experiments with 80/20 or phosphor bronze strings? I've never compared the two for the sake of a magnetic pickup, but in theory the 80/20 would be a bit more magnetic, right?

[fieldwrangler]

Thanks for all the info & observations. I do have a prototype that uses different mags for different strings, and it seems like this strategy's gonna survive into the final version.

I'm testing my stuff with an unusual set of strings sent to me by the guitar's maker; it's not a typical "steel string flat top" application. Don't actually know their composition, but I'll look into it. However, a near-absolute absence of string pull is a big priority of mine.

The brass plate is something that could come in handy for this or some other application.

In the case of the Barcus-Berrys there isn't much room for them to have done too much that won't be apparent from some passovers with the Hall-Sensor-on-a-Stick. (Still would like to see the patent that they used to proudly speak of but can't see to turn it up despite finding others applying to different BB transducers.) However, I am curious about specifics about the so-called "rare earth" single-coil-with-dummy-on-the-back; folks I respect really like this thing. Might hafta trash one for the cause.

Bob Palmieri

[Elias Graves]

I've been looking for a good solution to this problem for an archtop. My first attempt was n import Armstrong floating mini. No good. The bass strings didn't come through at all.
Second attempt was a P90. Better with the adjustable polepieces, but still not great.
I see where Kent armstrong handwounds as well as Lindy Fralin both offer pickups for use with bronze strings. Neither are forthcoming with recipes.
Currently working with Rose Pickups for a solution.

EG

[fieldwrangler]

I may have something for ya in about 6-8 weeks.

Bob Palmieri