Advanced magnetic circuit to improve both the solenoidal and magnetic functions of string instrument pickups with co-linear coil assemblies
View Patent ↗An electromagnetic pickup for a stringed musical instrument incorporating a magnetic structure placed between two elongated collinear coils of opposing polarity. The magnetic structure includes a number of ferromagnetic polepieces that extend through the collinear coils and two ferromagnetic moderator bars adjacent to and on opposite sides of the polepieces (within the area between the two coils) that are charged with one polarity by high coercive permanent magnets attached to the outer surface of the moderator bars.
1. A magnetic pickup for stringed musical instruments having ferromagnetic strings, comprising:
first and second bobbins each having upper and lower flange plates;
a plurality of spacers disposed between the first and second bobbins to create a gap between the flange plates of the first and second bobbins;
first and second coils wound around the first and second bobbins, respectively, the first and second coils each having an axis oriented perpendicular to a length of the ferromagnetic strings;
a plurality of ferromagnetic poles each extending through both of the first and second coils;
first and second ferromagnetic moderator bars each having an outward face oriented perpendicular to the upper and lower flange plates of the first and second bobbins and disposed in the gap between the first and second bobbins on opposite sides of the plurality of ferromagnetic poles, the first and second ferromagnetic moderator bars extending substantially a length of the first and second coils; and
a plurality of high coercive permanent magnets affixed to the outward face of the first and second ferromagnetic moderator bars.
2. The magnetic pickup according to claim 1 in which the first and second coils are disposed in an out of phase relationship.
3. The magnetic pickup assembly according to claim 1 , wherein the plurality of ferromagnetic poles is press fit into the first and second bobbins.
4. The magnetic pickup according to claim 1 , wherein the first and second coils and the plurality of ferromagnetic poles are elongated in a direction transverse to the length of the ferromagnetic strings.
5. The magnetic pickup according to claim 1 , further including first and second terminal plates disposed on opposite ends of the first and second ferromagnetic moderator bars.
6. The magnetic pickup according to claim 1 , wherein the plurality of high coercive permanent magnets has approximately half the mass of the plurality of ferromagnetic bars.
7. The magnetic pickup according to claim 1 wherein the plurality of high coercive permanent magnets is magnetically oriented parallel to a direction of the ferromagnetic strings, the high coercive permanent magnets being disposed with one magnetic polarity to the first and second ferromagnetic moderator bars which induce the same magnetic polarity into the plurality of ferromagnetic poles and the other magnetic polarity directed parallel to the ferromagnetic strings away from the magnetic pickup.
8. The magnetic pickup according to claim 1 in which the first and second coils are not directly influenced by a dipole function associated with the high coercive permanent magnets.
9. A magnetic pickup for stringed musical instruments, comprising:
first and second bobbins having upper and lower flange plates physically separated by spacers;
first and second coils wound around the first and second bobbins, respectively;
a plurality of ferromagnetic poles each extending through the first and second coils;
first and second ferromagnetic moderator bars each having an outward face oriented perpendicular to the flange plates of the first and second bobbins, the first and second ferromagnetic moderator bars being disposed between the first and second bobbins on opposite sides of the plurality of ferromagnetic poles; and
first and second permanent magnets affixed to the outward face of the first and second ferromagnetic moderator bars, respectively.
10. The magnetic pickup of claim 9 , further including third and fourth permanent magnets affixed to the outward face of the first and second ferromagnetic moderator bars, respectively, the third and fourth permanent magnets being physically separate from the first and second permanent magnets.
11. The magnetic pickup of claim 10 , wherein the permanent magnets have about half the mass of the ferromagnetic moderator bars.
12. The magnetic pickup of claim 9 , further including first and second terminal plates disposed on opposite ends of the first and second ferromagnetic moderator bars.
13. The magnetic pickup of claim 9 , wherein the first and second ferromagnetic moderator bars extend substantially a length of the first and second coils.
14. The magnetic pickup of claim 9 , wherein the plurality of ferromagnetic poles is press fit into the first and second bobbins.
15. A magnetic pickup for stringed musical instruments, comprising:
first and second bobbins physically separated by spacers;
first and second coils wound around the first and second bobbins, respectively;
a plurality of ferromagnetic poles each extending through the first and second coils;
first and second ferromagnetic moderator bars disposed between the first and second bobbins on opposite sides of the plurality of ferromagnetic poles; and
first and second permanent magnet affixed to an outward face of the first and second ferromagnetic moderator bars, respectively.
16. The magnetic pickup of claim 15 , further including third and fourth permanent magnets affixed to the outward face of the first and second ferromagnetic moderator bars, respectively, the third and fourth permanent magnets being physically separate from the first and second permanent magnets.
17. The magnetic pickup of claim 16 , wherein the permanent magnets have about half the mass of the ferromagnetic moderator bars.
18. The magnetic pickup of claim 15 , further including first and second terminal plates disposed on opposite ends of the first and second ferromagnetic moderator bars.
19. The magnetic pickup of claim 15 , wherein the first and second ferromagnetic moderator bars extend substantially a length of the first and second coils.
20. A method of making a magnetic pickup for stringed musical instruments, comprising:
providing first and second bobbins physically separated by spacers;
winding first and second coils around the first and second bobbins, respectively;
disposing a plurality of ferromagnetic poles through the first and second coils;
disposing first and second ferromagnetic moderator bars between the first and second bobbins on opposite sides of the plurality of ferromagnetic poles; and
affixing first and second permanent magnets to an outward face of the first and second ferromagnetic moderator bars, respectively.
21. The method of claim 20 , further including affixing third and fourth permanent magnets to the outward face of the first and second ferromagnetic moderator bars, respectively, the third and fourth permanent magnets being physically separate from the first and second permanent magnets.
22. The method of claim 21 , wherein the permanent magnets have about half the mass of the ferromagnetic moderator bars.
23. The method of claim 20 , further including disposing first and second terminal plates on opposite ends of the first and second ferromagnetic moderator bars.
24. The method of claim 20 , wherein the first and second ferromagnetic moderator bars extend substantially a length of the first and second coils.
25. The method of claim 20 , further including the step of press fitting the first and second ferromagnetic poles into the first and second bobbins.
26. A magnetic pickup for stringed musical instruments having ferromagnetic strings, the pickup comprising:
a primary upper coil, placed below the strings, to transduce magnetic energy of the vibrating strings into an electrical signal;
a secondary coil for neutralizing external oscillating fields, cancelling Eddy currents caused by the ferromagnetic poles, and determining harmonic spectrum of the signal generated by the primary coil;
a plurality of ferromagnetic poles extending through the primary and the secondary coils, the coils being axially spaced to extend perpendicular to a length of the strings;
first and second ferromagnetic bars disposed adjacent to each side of the ferromagnetic poles separating the primary and the secondary coils; and
high coercive rare earth permanent magnets affixed to the sides of the first and second ferromagnetic bars opposite the plurality of ferromagnetic poles.