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  • Vintage Strat PU vs contemporary replica: a test...

    Foreword : the goal of this topic is to share my experience and thoughts of hobbyist. But if someone wants to answer my questions, I’ll be grateful, of course.

    So, I’ve compared a genuine vintage 1962 Strat pickup with a contemporary replica built by a “big brand”, in the same guitar, with the same settings. Both PU’s are A5 single coils with staggered mags.

    Inductance @ 400hz are identical: 2,6H.

    Resonant peaks are virtually the same. Screenshot below. A slightly lower resonant frequency suggests a bit more capacitance in the vintage coil.

    DCR= 6k (vintage) vs 6,5k (replica).

    Gauss levels aren’t the same: according to the Teslameter used, the theoretically degaussed replica is still 1,25X more magnetized than the vintage PU.

    Harmonics spectrums are vastly different: the vintage PU has a prominent fundamental but provides 1/3 more upper harmonics. See the 2d screenshot below, where each PU amplifies a 1khz signal.

    Tone: the 62 sounds vintage, you guess it. The replica sounds good on its own but once compared to the vintage model, it exhibits an unpleasant upper mid spike.


    Hypothesis:

    -the superior harmonic richness of the vintage model is imputable to its hand-wound coil.

    -the higher inductance to resistance ratio in the vintage PU implies a different alnico formula, with a higher ferrous content in the old recipe.

    -I still wonder the reason why the staggering of the harmonics is so different while the resonant peaks are comparable. Winding patterns? Magnetic field ? Something else?


    Any thought?

    Dear pickup winders, if one of you feels able to match the features noticed in the vintage model, I’ll be happy to order him a couple of PU’s…

    I wish you all a merry Xmas and a happy New Year!

    Click image for larger version

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    Last edited by freefrog; 12-29-2013, 11:36 AM.

  • #2
    I suspect that you are right that the magnets are very different. That can even explain the difference in resonant frequency. Different levels of eddy currents alter both the imaginary and real parts of the impedance, resulting in a shift in the resonant frequency.

    I am puzzled by the harmonics that you show. If you are driving a pickup with a 1 KHz since wave, you should not see significant levels of harmonics. Pickups are a linear impedance when driven by reasonable signal levels.

    Comment


    • #3
      Originally posted by Mike Sulzer View Post
      I suspect that you are right that the magnets are very different. That can even explain the difference in resonant frequency. Different levels of eddy currents alter both the imaginary and real parts of the impedance, resulting in a shift in the resonant frequency.
      Thx!

      I am puzzled by the harmonics that you show. If you are driving a pickup with a 1 KHz since wave, you should not see significant levels of harmonics. Pickups are a linear impedance when driven by reasonable signal levels.
      The reason is that I don't use a sine wave in this case. :-)

      The guitar is played, @ the 19th fret, on the high E string (which reproduces roughly a 1khz signal). I record several minutes of ostinato picking with each PU. Then I select a short part of each track, where the level and attack are the most regular possible. A frequency analyzer set on "infinite" stacks the frequencies produced. That's it and it works reasonably well (in such a way that two screenshots of different tracks can stack exactly when the same gear and settings are used).

      I've tried to use an electromechanical stimulus mimicing the action of a pick on a string but I've not (yet) succeeded to make it work as I want. Maybe some day...

      Comment


      • #4
        So the frequency response is different. Again, possibly the magnets. Different magnets load the pickup differently.

        Comment


        • #5
          Stronger magnets will give you a brighter top end, so that makes sense. On a few humbuckers I made that were too edgy with A5 magnets, I switched to A2 magnets to make them mellower sounding. Degaussing the A5 would probably do something similar, but I never use degaussed magnets.

          Also the pickup wound slightly hotter would have a different resonant peak.
          It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein


          http://coneyislandguitars.com
          www.soundcloud.com/davidravenmoon

          Comment


          • #6
            interpretation

            Originally posted by freefrog View Post
            Foreword : the goal of this topic is to share my experience and thoughts of hobbyist. But if someone wants to answer my questions, I’ll be grateful, of course.

            So, I’ve compared a genuine vintage 1962 Strat pickup with a contemporary replica built by a “big brand”, in the same guitar, with the same settings. Both PU’s are A5 single coils with staggered mags.

            Inductance @ 400hz are identical: 2,6H.

            Resonant peaks are virtually the same. Screenshot below. A slightly lower resonant frequency suggests a bit more capacitance in the vintage coil.

            DCR= 6k (vintage) vs 6,5k (replica).

            Gauss levels aren’t the same: according to the Teslameter used, the theoretically degaussed replica is still 1,25X more magnetized than the vintage PU.

            Harmonics spectrums are vastly different: the vintage PU has a prominent fundamental but provides 1/3 more upper harmonics. See the 2d screenshot below, where each PU amplifies a 1khz signal.

            Tone: the 62 sounds vintage, you guess it. The replica sounds good on its own but once compared to the vintage model, it exhibits an unpleasant upper mid spike.


            Hypothesis:

            -the superior harmonic richness of the vintage model is imputable to its hand-wound coil.

            -the higher inductance to resistance ratio in the vintage PU implies a different alnico formula, with a higher ferrous content in the old recipe.

            -I still wonder the reason why the staggering of the harmonics is so different while the resonant peaks are comparable. Winding patterns? Magnetic field ? Something else?


            Any thought?

            Dear pickup winders, if one of you feels able to match the features noticed in the vintage model, I’ll be happy to order him a couple of PU’s…

            I wish you all a merry Xmas and a happy New Year!

            [ATTACH=CONFIG]26770[/ATTACH][ATTACH=CONFIG]26769[/ATTACH]
            In search of a solution I made these arguments:
            the signal generated by the vibrating string depends on the shape of the lines of the magnetic field in the space of the oscillation and the characteristics of the steel.
            The cases are:
            1 lines of force are substantially parallel and string saturated: signal proportional to the vertical vibration
            2 lines of force are substantially parallel and non-saturated string: signal distorted (greater when the string approaches the magnet)
            3 lines of force diverging and string saturated: signal resulting from both vertical and horizontal component of the oscillation
            4 lines of force diverging and string is not saturated: the resulting signal as 3, but with distortion.

            Since it is plausible that the difference is in the magnet, I suggest to consider it not cylindrical, but only the part actually magnetic of the same.
            The alnico magnet is made from a magnetic sub-lattice inter-penetrated in a non-magnetic one: the thermomagnetic treatment causes elongation and growth of magnetic parts and built a form-anisotropy.
            The resulting magnetic structure does not coincide with the cylinder form of the magnet, this causes that there are differences in the magnetic field.

            A possible experiment is to change the shape of the surface, for example, or by rounding the corners or creating a hole in the centre.

            Comment


            • #7
              Welcome to the EMF euler!

              Comment


              • #8
                Originally posted by euler View Post
                In search of a solution I made these arguments:
                the signal generated by the vibrating string depends on the shape of the lines of the magnetic field in the space of the oscillation and the characteristics of the steel.
                The cases are:
                1 lines of force are substantially parallel and string saturated: signal proportional to the vertical vibration
                2 lines of force are substantially parallel and non-saturated string: signal distorted (greater when the string approaches the magnet)
                3 lines of force diverging and string saturated: signal resulting from both vertical and horizontal component of the oscillation
                4 lines of force diverging and string is not saturated: the resulting signal as 3, but with distortion.

                Since it is plausible that the difference is in the magnet, I suggest to consider it not cylindrical, but only the part actually magnetic of the same.
                The alnico magnet is made from a magnetic sub-lattice inter-penetrated in a non-magnetic one: the thermomagnetic treatment causes elongation and growth of magnetic parts and built a form-anisotropy.
                The resulting magnetic structure does not coincide with the cylinder form of the magnet, this causes that there are differences in the magnetic field.

                A possible experiment is to change the shape of the surface, for example, or by rounding the corners or creating a hole in the centre.
                It's not about the AlNiCo as a magnet, it's about the AlNiCo as a pole piece.

                Think of the pickup more as a receiver of the flux that the magnetized string generates. The difference is in how that flux gets filtered in the pole piece.
                www.zexcoil.com

                Comment


                • #9
                  The function of the alnico magnet is solely to polarize the string. The vibration of the magnetized string is read from the coil.
                  The magnet has no other functions, possibly only affects the value of the inductance,due to the relatively low permeability.

                  Comment


                  • #10
                    Originally posted by euler View Post
                    The function of the alnico magnet is solely to polarize the string. The vibration of the magnetized string is read from the coil.
                    The magnet has no other functions, possibly only affects the value of the inductance,due to the relatively low permeability.
                    The magnet resides in the core of the coil.

                    Consider that the inductance of an air coil will be increased significantly if the air in the core is replaced by a permeable material. AlNiCo alloys have a relative permeability greater than 1 and the presence of AlNiCo in the core of the coil will significantly raise that coil's inductance. This will also shift the resonant frequency of the coil. Clearly then, the AlNiCo is playing a role in shaping the tonal response, beyond it's functional role in simply magnetizing the string.

                    Even further, different AlNiCo alloys, or even like AlNiCo alloys from different sources, will exhibit subtle and not so subtle differences in the inductance imparted to the coil, and also the shape of the frequency response.

                    So, the pole piece can easily be shown to have a significant effect on both the shape and the position of the resonant peak. This has a corresponding effect on the tonal response of the pickup. Substituting a material like iron or steel in the core of the coil will have an even more dramatic effect.

                    Some people here get it, but I think the single most overlooked aspect of pickup design is the role of the pole piece in shaping the "coloration" of the tonal response.
                    Last edited by ScottA; 10-01-2014, 05:41 AM.
                    www.zexcoil.com

                    Comment


                    • #11
                      Originally posted by euler View Post
                      .....possibly only affects the value of the inductance,due to the relatively low permeability.
                      Yes, the location and shape of that resonant response is the most important factor in the tone of the pickup. And let's see. If the relative permeability of alnico is 6, and of some steel is 200, does that mean that the inductance is 33 times greater with the steel? No, only about a factor of two or three at most. Only air completes the magnetic circuit, and so the inductance does not continue to increase much as the permeability is increased.

                      Also, even 6 is enough to affect how the time varying flux from the vibrating string is directed through the coil.

                      Comment


                      • #12
                        This all relates to something that has been on my mind.

                        Back in May I attended a wedding. My date was the sister of the groom, so I sat with the family. Her father has been in the magnet business for 40 years. He was even the head of Stackpole at one time. He knows absolutely nothing about instruments or pickups. But it was "common ground" I took advantage of it as I had just met this guy and knew of nothing else we had in common.

                        We spoke about his jobs and such and I told him what I did that was related. This led into a conversation about Alnico magnets. He said "There is only one source for "good" alnico these days and they are in California. Give me a call and I will put you in touch with them (I never did it, but I still have his card). I asked what he meant by "good" alnico and he said that most alnico on the market today would have been deemed "inferior" quality not terribly long ago. Mostly because it is made in factories with very loose tolerances (this guy is British, and has products made in Asia, so I know he isn't biased).

                        So now I have been left wondering. Is the alnico we are being supplied not optimal quality? Does it really make a difference in our pickups? And what about the alnico used in pickups "back in the day". Was it high quality, or was it made with the tolerances all over the map.

                        Not sure how it fits in, but I have thought about it a lot the past few months.
                        Last edited by Jim Shine; 10-03-2014, 12:29 AM.

                        Comment


                        • #13
                          Originally posted by Jim Shine View Post
                          This all relates to something that has been on my mind.

                          Back in May I attended a wedding. My date was the sister of the groom, so I sat with the family. Her father has been in the magnet business for 40 years. He was even the head of Stackpole at one time. He knows absolutely nothing about instruments or pickups. But it was "common ground" I took advantage of it as I had just met this guy and knew of nothing else we had in common.

                          We spoke about his jobs and such and I told him what I did that was related. This led into a conversation about Alnico magnets. He said "There is only one source for "good" alnico these days and they are in California. Give me a call and I will put you in touch with them (I never did it, but I still have his card). I asked what he meant by "good" alnico and he said that most alnico on the market today would have been deemed "inferior" quality not terribly long ago. Mostly because it is made in factories with very loose tolerances (this guy is British, and has products made in Asia, so I know he isn't biased).

                          So now I have been left wondering. Is the alnico we are being supplied not optimal quality? Does it really make a difference in our pickups? And what about the alnico used in pickups "back in the day". Was it high quality, or was it made with the tolerances all over the map.

                          Not sure how it fits in, but I have thought about it a lot the past few months.
                          I don't know if you can really apply "good" and "bad" to tonal response.

                          But certainly you can apply "different". It seems pretty clear that the modern alloys are different from the vintage alloys, I haven't personally studied this but the anecdotal evidence and reporting (things like the Blackguard book) and the limited studies that have been reported or at least alluded to (work by Ron Ellis for example) would seem to support it. "Better" or "worse" is largely a qualitative judgement, but I do think you can apply quantitative measures to things like "transparency" (for lack of a better term) that might be considered "better" in absolute terms.

                          Poor tolerances are absolutely an issue if you are trying to make a product with a consistent tonal response and I have no doubt that compositional changes, as an example, in AlNiCo alloys would result in changes in physical properties which would lead directly to changes in tonal characteristics.

                          From that standpoint, and if this guy's position is valid, modern pickups would be more hit and miss anyway.
                          www.zexcoil.com

                          Comment


                          • #14
                            Originally posted by ScottA View Post

                            From that standpoint, and if this guy's position is valid, modern pickups would be more hit and miss anyway.
                            At some point you have to move on. Common modern materials are consistent. If you find a way to make pickups with the tone you want from these materials, then you can make a consistent product.

                            Comment


                            • #15
                              If in fact there are only a few domestic foundries for Alnico then the California one should be easy to determine should anyone care.
                              it's not Adams Magnetics (Elmhurst, IL)
                              It's not Arnold magnetics. (Rochester, NY)
                              It's not Bunting Magnetics (Newton, KS)
                              Not Dura Magnetics (Syvania, OH)
                              Thomas and Skinner (Indianapolis, IN and Fairfield, CT)
                              That leaves possibly:
                              Magnet Sales & Manufacturing Inc.
                              11248 Playa Court
                              Culver City CA 90230
                              800-421-6692
                              Alnico Rod Magnets
                              Last edited by David King; 10-03-2014, 09:30 PM.

                              Comment

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