Introducing: The Feedback Catcher

Okay, time for something a little different. As people who know me will no doubt be aware, I happen to be fascinated by audio feedback and home-made electronics. I was messing about the other day and I invented a cool little noise-making device I currently call the Feedback Catcher.

In simple terms, the Feedback Catcher consists of a thin membrane on a frame that picks up vibrations in the air, with a contact microphone attached to its surface, then fed through some distortion pedals, into a cheap amplifier. The way the Feedback Catcher works is very simple indeed: it creates a feedback loop not unlike a guitar, and by positioning the device in various ways relative to the amplifier, you can modify pitch and tone in various ways. It is similar in theory to a Theremin except nowhere near as precise or predictable. The musical applications of this device are limited, unless, like me, you like noise, in which case they are near endless.

To create your own Feedback Catcher, follow this simple unillustrated guide.

Items required:

  • Membrane with frame (I am using a child’s outdoor toy racket designed to make noise, I have also experimented with tinfoil on a card frame)
  • One piezo transducer (from Maplin)
  • One 1/4 inch MONO audio connector socket (from Maplin)
  • Some wire
  • Some heat shrink tubing or electrical tape
  • Soldering iron and solder
  • Some tape to attach the contact to the membrane
  • Effects pedals of your choice (ie. experiment)

Your main task here is to wire up the contact microphone. This guide is more or less pilfered from this guide here, but the process is self-explanatory if you understand basic electronics. I’m going to assume some basic competence with soldering, because that’s about all I have and I managed to pull it off.

  1. Take the audio connector socket and unscrew its casing. There should be at least two contacts, usually three.
  2. Cut two lengths of wire to the length of your choosing (I suggest maybe 20cm), and strip both ends.
  3. Solder the wires you just cut to the contacts of the connector. Since this will be a mono device, there should be three metal parts, one long protruding one, and two set into the plastic. One wire should be soldered to the long contact, and the other should be soldered across the two.
  4. Add some heat shrink tubing to (heat with a hair dryer or on a radiator to shrink it) or some tape to keep the wires in place and tidy, but make sure and leave the two trailing ends of the wires free.
  5. Take the piezo transducer, and strip the ends of its wires. Slide some heat shrink on to the wires now if you’re using it, those using tape can wait.
  6. Solder these two wires to the two wires from the connector. It doesn’t really matter which one is which.
  7. For those using heat shrink, shrink the tubing over the soldered connections. Tape people can tape round these points.
  8. Your contact microphone is ready. Plug it into an amplifier with a standard guitar type cable, tape it to some surfaces and see what noises you can pick up.
  9. Next, get your membrane/frame construction (in this example, the toy racket) and tape the contact to the membrane, and the trailing wires and connector to the frame.
  10. You’re done!

The advantage of the racket is that it already has a handle. When using the Feedback Catcher, some distortion effects are very important because otherwise you have to work with very high volume and it tends to go from silent to squealing high pitches without much variation in between. Experimenting with effects produces all kinds of interesting harmonic variations, I particularly recommend some wah or other filter-type effects. I have made a little video of the device in practice so you can see the kind of wonderfully awful noise it can make.

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