Tuesday, April 27, 2010

Diddley Bow

Hello again everyone!

This semester has been a busy one, with hosting the 2010 SEAMUS National Conference, teaching, recovering, etc. I'm teaching a course in circuit bending/hacking this semester and it's gone quite well.

We've explored all kinds of interesting circuits, based primarily on the work of Nic Collins. This has included a variety of microphones, from contact microphones to electret mics. We've also built a variety of drivers, buzzers and oscillators.

One of the most interesting projects was built off the work of Ranjit Bhatnagar, a NYC based artist. He was featured on NPR for his homemade guitars, and I instantly knew that this was a project we needed to try.

The basic ingredients are:

-Piece of wood
-Guitar string
-Magnet
-Magnet wire
-Eye bolt
-Wood Screws
-Sewing bobbin
-Corner brace
-Various nuts and washers (I used wingnuts too)

It's pretty easy from there. I drilled a small hole in one end of the wood for the guitar string, big enough to fit the string through but small enough to give the anchor a place to stop. Then I attached the brace on the other end of the wood, tied the string to the eyebolt and tightened it. The wingnut allows for quick tuning.

The pickup is the "hard" part. I simply wound the magnet wire around the bobbin, leaving about 6 inches from each end loose. I stuck the magnet in the center of the bobbin, then hot glued the whole thing together. (NOTE: you might want to place the magnet close to one end of the bobbing, which will become the top. I achieved much better results when I did this!). A dab of hot glue attached the pickup to the wood under the string, and then I simply attached the loose wires to a female audio jack (in my case I was using a tiny amp that needed an 1/8th inch connection, but a guitar amp needs a 1/4 inch connection). Plug it in and jam out!

But wait Twombly, there aren't any fancy circuits or power...or...well...commercial parts! How does it work?


WARNING: SCIENCE CONTENT!

It's pretty simple, really. The magnet creates a small field that the string interferes with when it vibrates. The magnet wire picks up a tiny amount of electricity from this field and sends it along to the amplifier, which...well...amplifies the sound. With a tiny amp like the ones we use in class (battery powered, 1/2 watt of pure audio bliss), it is easy to overdrive the amp, which is how those Chicago blues men got such great fuzz from their early electric guitars.

Now, what I built was technically a Diddley Bow, a one-stringed instrument that is most often played with a metal or glass slide. It's a lot like a lap guitar, but can be used for all sorts of interesting things.

Here is Seasick Steve performing one of his great R&B tunes on Diddley Bow, Save Me:

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