The idea was simple and genius (not my btw): Using the p-bass pickups as a sound transformer.

The majority of the DIY stomp boxes I saw so far have a piezo buzzer for this goal.

As with any piezo element, it comes with 2 common issues:

1. “Dirtiness” of the sound. Not only the kick of your foot is transmitted but all possible squicks and even the smallest rustles.

2. Huge feedback. You have to be a sound engineering guru to get an acceptable sound. So it is loud enough and without the self-generated feedback sound.

The regular magnetic pickup is supposed to solve both problems at least the big part of it.

Just because it’s only able to transmit the vibrations of the metal object.

In the case of the guitar, it is the vibration of the string. But you can use any metal object for this goal.

Supplies

Cohiba Cigar Box.
P-bass pickups.
Self-adhesive aluminum coil.
1/4" Guitar/Phone Jack.
Self-adhesive double 2-sided Sticky Strong Mounting Tape.
String Replacing Metal Object.

Step 1: Step 1. Drilling the Cigar Box.

Drill a hole for the 1/4″ jack (#4 above).

You can use one of the end faces of the box but not the one you plan turn toward to you while playing.

I usually use left/right side ends but the top side end might be even better.

Oh. And I turn the box to me with the side opposite to the one which has a lock.

Step 2: Shielding. This Step Is Fairly Simple.

Just cover tightly the interior sides of the box with the self-adhesive aluminum foil.

All sides including the cover lid.

Don’t leave the uncovered spaces between the stripes.

The overlapping is better.

For example, take a look at the resulting image at the bottom.

Step 3: Installing Jack.

I guess this step doesn’t need any detailed directions.

Just put it through and tighten the nut. Don’t forget the washer though.

Step 4: Mounting the Pickups.

The position for the p-bass pickups is not really important.

Just as a rule of thumb the central position should be the best because the maximum of the vibration occurs in the center.

Firstly stick two stripes of mounting tape on the bottom sides of the pickups.

Then take them in one hand ready to put in place and remove the protecting paper with another hand and stick them to the center of the bottom with wires side facing the installed jack.

Step 5: Connecting the Pickups to the Jack.

This is the only step where you probably will need some special tool. I mean a soldering iron.

I saw some people just tying the wire to the jack contact holes.

Well, it might work. But not for a long time.

So if you want a good device then solder it.

Remember that the black wire is for the ground.

Actually, I’m not sure that polarity in this case is important.

But I’m trying to be just accurate here.

Step 6: Final. Installing the "string"

As I said I used the lid from the small Fisherman’s Friend metal box.

Just because this is the first suitable thing I was able to find.

But feel free to use whatever you can find.

Any piece of metal which is thin enough to produce the vibrations will work. Now the important part. The gap between the metal plate and the pickup.

I would vote for 2mm max. The closer – the better the response.

But at the same time, you have to make sure the plate won’t touch the pickup during the hit. While using the mounting sticky tape put it on the 2 far ends of the pate so the middle is left free for better vibrations.

But remember that it has to hold the plate strong enough to fight the pickup magnet attraction. Put 2 or even more layers of sticky tape (one on one) if you need to set the plate closer to the pickup.