Any idea what alloy Duncan uses on their keepers and polepieces?

[NateRS]

The only parts from the sd 59 that I swapped into my pickup were the pole pieces and the keeper bar so I'm confident it was those that made the tone change. That's an interesting theory about it possibly being the adfx baseplate being bright, because it was was one of theirs that I used on this one. I never even thought about baseplate changing sound since they're all nickel silver for the most part (although some have the threaded holes for the poles), but that would be interesting to test.

Did you try to isolate the added SD parts?
To see if it was the slug bobbin, screw bobbin, keeper, or all that effected the tone?
If you could isolate which part made the difference, then you would have less parts to analyze?
If you're using the ADFX baseplate?
I found it to be unusually bright, compared to other brands.
Also Bright can be good if you're adding a tone robbing cover?

On the laminated keeper?
Besides the added building complexity issues, If the tone is already too bright, IMO the laminated keeper could just make it worse.
T

[NateRS]

Thanks Jason, that would actually be awesome. I called a local lab a while back about a metallurgy test but they wanted $200+ just to test a screw. I'm guessing the price probably depends on the type of test though. Do you have a place you recommend for the spectrometer test?

If you only need to test a couple of parts mass spectrometry is not very expensive. I have had alot of parts burned and I think we pay about $75 per test and youll find out exactly what the composition is. Lots of places that do it to select from.

[NateRS]

Actually I may have spoke too soon, just found this test online looks promising for $49 http://www.rotometals.com/product-p/...FYqPfgod8WAOhw

Thanks Jason, that would actually be awesome. I called a local lab a while back about a metallurgy test but they wanted $200+ just to test a screw. I'm guessing the price probably depends on the type of test though. Do you have a place you recommend for the spectrometer test?

[Joe Gwinn]

Yep that is what I meant.

i am thinking that it does not take very much difference to be audible. Even untrained people hear differences in damping as a different sounding instrument. A guitarist or pickup maker listens a lot more and probably develops a high sensitivity to this.

Looking here: Properties of soft magnetic materials

The relative permeabilities for some steels at low applied field levels are (steel, relative perm.):

1006 1530

1008 1486

1010 460

1018 790

1020 151

1030 241

There appears to be a significant variation, and not necessarily so easy to understand, but I think some of the audible differences would be significant.

The trend is that the higher the carbon percentage, the lower the magnetic permeability. Electrical conductivity will also vary. A useful summary comparison is skin depth at 1 KHz by carbon percentage (~alloy number).

[jack briggs]

Yep that is what I meant.

i am thinking that it does not take very much difference to be audible. Even untrained people hear differences in damping as a different sounding instrument. A guitarist or pickup maker listens a lot more and probably develops a high sensitivity to this.

Lokking here: Properties of soft magnetic materials

The relative permeabilities for some steels at low applied field levels are (steel, relative perm.):

1006 1530

1008 1486

1010 460

1018 790

1020 151

1030 241

There appears to be a significant variation, and not necessarily so easy to understand, but I think some of the audible differences would be significant.

I've found audible differences to be subtle, but discernible.



cheers,

[Mike Sulzer]

The trend is that the higher the carbon percentage, the lower the magnetic permeability. Electrical conductivity will also vary. A useful summary comparison is skin depth at 1 KHz by carbon percentage (~alloy number).

Right, I can see the trend. The difficult thing to understand is the large deviations from the trend.

[Mike Sulzer]

I've found audible differences to be subtle, but discernible.



cheers,

That sounds about right!

[John Kolbeck]

Electrical conductivity will also vary. A useful summary comparison is skin depth at 1 KHz by carbon percentage (~alloy number).

Do you happen to know roughly how much variation?

[Joe Gwinn]

Do you happen to know roughly how much variation?

Not offhand, but a search on the alloy number and the word resistivity (expressed in ohm-meters or mivro-ohm centimeters or the like) should bring them up.

[Joe Gwinn]

Right, I can see the trend. The difficult thing to understand is the large deviations from the trend.

Well, first thing is to figure out the skin depths and see if the sonic trend makes more sense.

Also, in the alloys with more carbon, hardening will matter, as will annealing.

And there will be alloying elements other than carbon.

My guess is that all that matters in electrical resistivity and magnetic permeability, and that materials with the same skin depth will sound alike. This can be experimentally tested.

[bbsailor]

Well, first thing is to figure out the skin depths and see if the sonic trend makes more sense.

Also, in the alloys with more carbon, hardening will matter, as will annealing.

And there will be alloying elements other than carbon.

My guess is that all that matters in electrical resistivity and magnetic permeability, and that materials with the same skin depth will sound alike. This can be experimentally tested.

Can anyone state or estimate the maximum frequency or harmonic that a magnetic type pickup can potentially produce? We all know that the maximum frequency range of typical electric guitar amps and speakers is near 5KHz but could a magnetic pickup, not restricted by traditional design constraints, detect any harmonic energy between 5KHz and 10KHz?

Thanks

Joseph J. Rogowski

[Joe Gwinn]

Can anyone state or estimate the maximum frequency or harmonic that a magnetic type pickup can potentially produce? We all know that the maximum frequency range of typical electric guitar amps and speakers is near 5KHz but could a magnetic pickup, not restricted by traditional design constraints, detect any harmonic energy between 5KHz and 10KHz?

Oh, sure. Especially on attack transients. Probably no higher than the self-resonant frequency, but one can make that frequency well in excess of human hearing. Active pickups can do this, as can low-impedance pickups. To handle the transients, a 50 KHz passband is what the microphone folk say is necessary to reproduce the transients. There was a big angry thread on this a while ago.

[bbsailor]

Oh, sure. Especially on attack transients. Probably no higher than the self-resonant frequency, but one can make that frequency well in excess of human hearing. Active pickups can do this, as can low-impedance pickups. To handle the transients, a 50 KHz passband is what the microphone folk say is necessary to reproduce the transients. There was a big angry thread on this a while ago.

Thanks for your quick answer. Can you identify the "big angry thread" that discussed this issue? The reason why I asked was to obtain some objective consensus and/or input about the most practical high frequency harmonics that a guitar can produce that make a real listening difference in a pickup design. With current based pickup designs, using a current transformer (CT), I am contemplating using Litz type wire to ensure that the current at the practical upper high frequency limit is not attenuated by the skin effect of the string loop wire inducing current into the CT. I am just trying to target an optimum design using practical frequency limits and measurement techniques.

Should I shoot for a 50KHz upper limit even if there are no known harmonic components in the guitar string output up that high?

Again, thanks for your input.

Joseph J. Rogowski

[David King]

Rick Turner had some interesting things to say about using Litz wire it this thread:
http://music-electronics-forum.com/t36453/ Not sure if or how that relates to skin depth on low to medium carbon polepieces.
Well upon rereading the thread you were all involved in it so it should be old news.

[bbsailor]

Rick Turner had some interesting things to say about using Litz wire it this thread:
http://music-electronics-forum.com/t36453/ Not sure if or how that relates to skin depth on low to medium carbon polepieces.
Well upon rereading the thread you were all involved in it so it should be old news.

David,

There are many things that affect the final audible sound of a pickup including: coil turn numbers, wire gauge, insulation thickness, core inductance and eddy current influences, on board volume pot and tone pot loading, and most importantly the cable capacitance as it relates to the pickup coil impedance. This thread deals with more subtle factors such as the effect of eddy currents in various metals or the effect of various metals on the inductance of the pickup coil itself. Since guitar pickups typically use AWG 42 or 43 magnet wire, there is little concern for skin effect in this type of thin wire. However, in current based pickups with thick string loops, the skin effect is more a potential sound effecting characteristic. I was just trying to understand a commonly agreed upon upper harmonic limit to base my optimum pickup design calculations. Maybe this is the wrong place to ponder these thoughts but I think they are closely related?

Joseph J. Rogowski