This Instructable will show you how to make an analog tape echo effect for use with electric guitar or any other audio source. The cassette tape echo employs the same basic principle as legendary vintage units like the Roland Space Echo or more primitive reel-to-reel tape echo setups, but using much cheaper and more readily-available used cassette technology. Unlike the classic commercially-made units, this project has more limited features, more unpredictable behavior, and a noisier, more lo-fi sound-- whether those qualities are desirable or not are up to you.
How It Works
Before starting, it's important to wrap your head around the basic principles behind all analog tape echoes and to an extent magnetic tape recording in general. To put it briefly, cassette and reel-to-reel recorders are able to record, play back, and erase audio using tape heads that generate magnetic fields to align tiny metal particles on the tape. Old reel-to-reel recorders have three separate dedicated tape heads for erase, record, and play functions, arranged in that order with respect to the direction of the tape's travel. Since the record and play heads are separate, there is a few milliseconds' delay between the time the audio is recorded to tape with the record head and the time it's played back with the play head, depending on the distance between the two heads and the tape speed.
At some point, audio engineers figured out how to create an echo effect by taking the output of the play head and mixing it with the audio source being sent to the record head, creating a feedback loop. This is crudely illustrated in the diagrams above, with the audio source being an electric guitar. The commercial tape echo units like the Space Echo use the same basic signal flow plus some additional features.
Making a tape echo out of a cassette recorder is tricky because, unlike reel-to-reels, most cassette recorders have a combined record/play head instead of separate record and play heads (Those who own a high-end 3-head cassette deck might be interested in building the Echo-Matic instead). To make it work, you are going to have to attach an extra play head to a working tape recorder, amplify the signal of that tape head somehow, and hack up a cassette shell so that it will accept the extra play head.
- Basic soldering, splicing wire
- Understanding audio signal flow and using a mixer
- Patience to work with something as thin and finicky as cassette tape
- Four-track cassette recorder* with at least two inputs (I used the Tascam Porta02)
- Regular cassette player (preferably name-brand and '90s-era for higher fidelity, i.e. Sony Walkman or something similar)
- Blank cassette
- Scotch tape or special splicing tape
- Small piece of foam taken off a foam brush
- Thin hookup wire
- Heat shrink tubing
- 500 Ohm, 2W linear-taper potentiometer (value may vary based on your recorder)
- Various resistors (to fine-tune the value of your potentiometer, if necessary)
*Since a four-track recorder is just a tape recorder with a built in mixer, you can probably just use a separate mixer and two regular cassette players to make this (although I've never tried), which might make the project even cheaper to build. I chose to use the Porta02 because it's more convenient to move around and because I already had one. The fact that it can record four separate tracks isn't necessary for the project.
- Soldering iron
- Regular and jeweler's screwdrivers
- Needlenose pliers, wrenches
- Hacksaw or Dremel