A tin banjo

A 4-string banjo (of sorts) designed around an old biscuit tin.

The instrument has a piezo pickup fitted beneath the bridge. Scale length is 25.5 inches, which is the same as many guitars and thus slightly shorter than the most common lengths for banjos. It is tuned D-G-B-d.

My knowledge of banjos is quite limited, coming mainly from reading about them and seeing them in shops. Aspects of the design (especially the neck and the arrangement of the tuners) were derived from successful features of the 3-string tin box guitar, which I built previously.

This is what it sounds like (please forgive the playing - I had not played a banjo before building this one and I was sort of improvising):

  • With pickup fed directly into mic input of laptop - click here sound sample
  • With pickup output fed through the clean channel of a guitar amp - click here sound sample
  • Just the acoustic sound recorded with a cheap "computer" mic - click here sound sample

Below are some pictures of the construction. Clicking on the images will take you to larger, higher resolution versions.

 

Banjo

Tin used for body/resonator

The tin before construction

The pickup was made from part of an Artec PP-402 split pickup designed for 6-string instruments such as acoustic guitars. By carefully separating the leads for the two sections I ended up with two pickups - a 4-string width one used for the banjo and a 2-string width one for use on some future instrument.

Some builders of cigar box guitars use improvised piezo pickups made from piezo buzzers sold by the likes of Radio Shack, however the pickup used here is very cheap (even more so when you consider the two-for-the-price-of-one arrangement). I bought mine for £8 from Axes-R-Us.

Pickup before construction

Pickup in place under bridge

The pickup fitted in place underneath the bridge. The bridge was filed from a piece of square section aluminium bar (I cut a shallow slot into the underside to help hold the pickup in the correct place). The pickup is the brass strip which is just about visible in the gap between the bridge and the surface of the tin body.

The neck is made from an offcut of a timber called sapele (a member of the mahogany family). It has 18 frets.

Neck

Zero fret arrangement at nut

I chose a "zero fret" arrangement in place of a conventional nut. I've seen this feature on Gretsch guitars and it seems to me a very neat way of getting a good action at the nut end of the neck.

A rear view of the finished instrument with the back removed to show the through-neck design and very basic circuitry.

The black wire is a coaxial lead from the pickup to the volume control.

The black rectangles near the neck-body join are a piece of rubber foam, which I used to "tune" the base of the tin and to suppress some unwanted resonance.

Rear view with back open

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