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For all you guys making a wide variety of stringed instruments here is a new way to make a quick and simple pickup. All you need is a small, miniature audio transformer with 8 ohms on one side and from 15,000 to 20,000 ohms (or higher if you can find one) on the other side. These transformers are typically about .75" by .75" so one or more can easily fit in your instrument. Typically, you use one transformer per string.

To estimate the step up ratio of the transformer do this simple math. An 8 ohm to 20,000 ohm transformer is 20,000 divided by 8 or 2500. Now take the square root of 2500 and you get 50. So the transformer increases the induced voltage on the string by about 50. With a good low resistance wire connection between each end of the strings to the 8 ohm side of the transformer you will get about .002 to .003 volts on the transformer primary and when measured at the output of the transformer will be about 0.1 volts and be in the same range as a Fender single coil pickup. Experiment with magnet types, sizes and lengths under the strings to fine tune to your ear. 

Here is how to do it. Obtain four alligator clip leads. Attach one alligator clip to a string behind the nut and one alligator clip on the same string behind the bridge.  Attach these two alligator clips to the 8 ohm side of the miniature audio transformer.  Alligator clip the high impedance side of the audio transformer to a guitar cable plug.  Attach this guitar cable into your guitar amp hand hold a magnet (any type) near the string and when the string is plucked, you will hear sound.

The above experiment is just to quickly allow you to experience this moving coil type of pickup. It works very much like a ribbon microphone for those who might want to dive more deeply into why it works. You can do a web search for "moving coil pickup for the technically curious" where I initially posed this concept.

Based on my own research here is what I have learned to optimize this type of pickup for guitars.

The voltage level induced into a vibrating string is dependent of the length of the magnetic field along the string length. Try to obtain a long and narrow magnet such as .25" wide by 2" long  by .125" thick. Hold either the N or S pole of the magnet under and across the string. Pluck the string and listen and turn the magnet 90 degrees so it now lays parallel to the string and listen to the sound level increase as a longer part of the string is now magnetized.

Guitar strings typically have a DC resistance of about .5 ohms. Thinner strings have a higher resistance. But, in this range of string resistance, an 8 ohm transformer puts a load of about 10 higher than the source impedance of the string so the voltage induced on the string is not loaded down too much by the transformer and the maximum output is achieved. 

For those of you wanting to refine this design into a finished instrument do this.

Design the nut to be the common ground return point by making a nut from good conducting metal. Attach the nut to the truss rod or another ground return that has a low resistance to not loose to much induced string voltage in the wires leading to the transformer. Attach all the transformer primaries (8 ohm side) to this common ground return that allows the transformers to be mounted in the body near the bridge. Mount the transformers near the neck/body or bridge end of each string wires to the other wire on the transformer primary. 

You will have a totally independent output from each string or you can combine the strings by putting all the transformer secondaries in series. With separate outputs you can send the output of each string to a mixer and adjust the volume of each string individually.  I did this by putting a thick copper strip under my guitar fingerboard just above the truss rod and attached this copper strip to a brass nut. I mounted 6 miniature transformers under the 4" hole to the heel of the neck. Then I put 6 copper rivets in the bridge to thread the strings through. I soldered a wire to each rivet and ran these six wires to the six transformers on the heal of the neck. Then I obtained a multi pin connector set and a 6 strand shielded wire and attached one strand to the high impedance side of each transformer and grounded one side of the transformer to the shield. On the other end of the cable I made breakout with six single conductor cables with a standard guitar plug on the end to plug into a six channel mic mixer. Thus, I had individual string control of EQ, L/R  balance, and volume.

I hope this gives you some ideas for a new and unique way to make a pickups for your Cigarbox Guitars.

Let me know how it works when you try it.

Thanks

Joseph J. Rogowski