Electric feedback guitar

An electric stringed instrument such as a guitar having a sound reproducing element on the top of the neck for feeding the tones of the strings back into the guitar. (A sound reproducing element being a speaker or an electromagnetic transducer.) The tones of the strings are sent from the pickup to an amplifier and then to the sound reproducing element. This feedback will either prolong the note played or one of its harmonics or will not have any effect depending upon which note is played. Two wires are imbedded in the back of the neck to bring the electric signal to the sound reproducing element.

U.S. PATENT DOCUMENTS CITED 
U.S. Pat. No. 518,775; 4/1894; Birrer. 
U.S. Pat. No. 3,357,291; 12/1967; Carmichael; 84/267. 
U.S. Pat. No. 3,696,700; 10/1972; Berardi; 84/291. 
U.S. Pat. No. 3,449,531; 6/1969; Ashworth; 179/115. 
FIELD OF INVENTION 
The invention relates to stringed instruments class 84, subclass 267, and 
subclass 293. 
SUMMARY 
An electric stringed instrument such as a guitar having a sound reproducing 
element on the top of the neck for feeding the tones of the strings back 
into the guitar. (A sound reproducing element being a speaker or an 
electromagnetic transducer.) The tones of the strings are sent from the 
pickup to an amplifier and then to the sound reproducing element. This 
feedback will either prolong the note played or one of its harmonics or 
will not have any effect depending upon which note is played. 
DISCUSSION OF PRIOR ART 
The only sound modification found in a musical instrument neck was Birrer 
U.S. Pat. No. 518,775 which disclosed an acoustic sound hole in the head 
of the neck (year--1894). 
A speaker is built into a guitar body in Carmichael U.S. Pat. No. 
3,357,291, for the purpose of amplification (col. 1; line 15). This 
invention assures that the speaker vibrations do not effect the resonant 
qualities of the top panel (col. 2; line 69); thereby suppressing 
feedback. 
Berardi in U.S. Pat. No. 3,696,700 attempts to reduce feedback in stringed 
instruments containing speakers (col. 1; line 19). In contrast to prior 
art, my invention purposely induces feedback and purposely effects the 
resonance of the instrument. 
Groupp in U.S. Pat. No. 4,245,540 purposely induces feedback of tones. 
Because the speaker is in the body of the guitar and is very close to the 
magnetic pickups, Groupp employs acoustic shielding and magnetic 
shielding. The invention herein described does not need any shielding 
because of the large distance between the pickups and the transducer on 
top of the neck. Groupp is satisfied with only 3 watts of audio power 
(Col. 6; line 41); whereas this invention can use more than 20 
watts--creating very extreme feedback effects. 
Ashworth in U.S. Pat. No. 3,449,531 invented an electro-mechanical 
transducer. This device has an advantage over the speaker as the sound 
reproducing element of the invention: it is much quieter. 
THE OBJECT OF THE INVENTION 
The object of the invention is to provide musicians a guitar with improved 
feedback capabilities. Standard guitars must be amplified very very loud 
to induce feedback. As the volume is diminished the feedback diminishes. 
Guitars with speakers in the body have an advantage in feedback over 
standard guitars in that the speakers are attached directly to the wood, 
thus transmitting sound vibrations more efficiently. Unfortunately, the 
volume of the speaker cannot be turned up very loud without emitting a 
high squeeling noise; thus feedback is at a diminished level. 
The invention herein described overcomes this limitation by attaching the 
sound reproducing element on top of the neck. With approximately 15-25 
more inches between the sound reproducing element and the pickup, the 
volume of the sound reproducing element can be further increased before 
emitting the high squeeling noise. By increasing the sound vibrations into 
the wood, feedback is improved.

DESCRIPTION OF STRUCTURE 
The best mode of the invention is described physically as follows: 
In FIG. 1 an electro-magnetic transducer 10 is screwed into the back of the 
peghead 11 of a guitar neck 12. If the transducer 10 is unavailable for 
purchase, make one following the instructions in U.S. Pat. No. 3,449,531. 
Cut two grooves 13 down the back of the neck 12 from the peghead 11 all the 
way to the bottom 14. Press bare wires 15 gauge #22 into the grooves 13. 
Brush lacquer over the grooves 13 on top of the copper wires 15 as 
protective sealing. 
Wrap the copper wires 15 around the screws 16 on the back of the peghead 11 
and around the screws 17 on the bottom 14 of the neck 12. Connect the 
transducer 10 to copper wires 15 at screws 16. 
As in FIG. 2, drill a 1/4" diameter hole 18 from the center of the neck 
cavity 19 in the solid wood body 20 to the pickup cavity 21. Carve a small 
rectangle 22 in the wall of the neck cavity 19 for the heads of screws 17 
to fit in. Drill a 1/4" diameter hole 23 between the pickup cavity 21 and 
the electronic control cavity 24. 
Install a 1/4" chassis mount speaker jack in the electronic control cavity 
24 using a nonconductive grommet to avoid grounding complications. Run 
two-conductor speaker wire from the 1/4" speaker jack through hole 23 to 
the pickup cavity 21 and then through hole 18 and out rectangle 22 leaving 
about 3" of wire protruding out. Attach this slack speaker wire to the 
bottom 14 of the neck 12 by screws 17. 
Pull the slack speaker wire back into the pickup cavity 21 as you place the 
neck 12 in place in the neck cavity 19. Insert wood screws through the 
four mounting holes 25 and bolt the neck 12 to the body 20. 
I suggest using a separate amplifier for the sound reproducing element in 
addition to the normal amplifier for the listening audience. The musician 
could then lower the volume for his listening audience without loosing 
feedback. 
I also suggest using compression circuitry for the signal going into the 
amplifier for the sound reproducing element. This will flatten the volume 
peaks of the plucked strings, thus improving the signal for continuous 
feedback flow. 
The guitar may use one electric guitar pickup for both amplifiers (use a 
Y-JACK); or the guitar may use two pickups (one for each amplifier). Using 
two pickups allows the musician to adjust the pole pieces differently. 
A very useful addition to the invention is to install a switch for 
reversing the electric signal in the two-conductor speaker wire. Different 
harmonics are enhanced when the polarity of the electromagnet in the 
transducer 10 is reversed. This switch may be installed in the electronic 
control cavity 24, or in a foot operable switch box, or both. 
OTHER EMBODIMENTS 
Some musicians would prefer to buy a feedback inducing device which they 
could clamp to a guitar they already own. FIG. 3 shows a transducer 10 
attached to a 11/2" wide, 1/8" thick piece of aluminum 26 which is bent 
backward with 1/2" spacing 27. Fit the open end 28 of the aluminum onto a 
peghead of a stringed instrument and tighten the screws 29, thus clamping 
the sound reproducing element onto the neck. Mount a 1/4" chassis mount 
speaker jack 30 in the aluminum 26 using a rubber or nylon grommet 31. 
Because the jack 30 is larger than the 1/2" spacing 27, an accommodating 
hole 32 must be drilled in the opposite site of the clamp. Connect the 
transducer 10 to the speaker jack 30 with two-conductor speaker wire 33. 
Also possible (not shown in FIG. 3), the clamp may be extended longer to 
add a reversing switch for the two-conductor speaker wire 33. 
Some musicians would prefer to buy only the neck 12 of the invention herein 
described. They would then modify the body 20 of the guitar they already 
own with hole 18 and rectangle 22 and attach the neck 12.