Homebrew Drum Computer Delay Lines
dkelvey at hotmail.com
Sun Dec 16 13:25:19 CST 2007
> From: bnansel at bigpond.net.au
> I've come across a reference to a reverb unit made with a garden
> hose, speaker, and microphone. Would something as bone-headed as
> this work as a data delay line?
> I've read that mercury was used in delay lines because it was a
> better impedance match with quartz transducers, but wouldn't water
> work nearly as well? Everything would need to be kept at a constant
> temperature, and no doubt there would be some dispersion of the
> compression waves. It's my understanding that a lot of materials
> were tried for delay lines, but that mercury was the "best."
The primary reason for mercury was the slow propagation
time, not impedance. The slower, the more bits per length.
Mechanical transformers are not all that hard to create.
Early programmable calculators use a different mode of
transmission. They use rotation of a wire. The twisting
goes slower along the wire than a compression wave because
it is the rotational inertia compared to the spring of the wire.
Compressional waves tend to travel faster. In something like
mercury, being a fluid, can only transmit compressional waves
( except other surface waves like ocean waves ).
A wire can use either compressional or rotational. The rotational
is slower and can hold more date for distance.
The important thing for any of these is absorbing any reflection.
This means that impedance matching and possible dampening
will make all the difference.
Surface can have vertical as well as shear waves but these
are harder to control. The rotational wave is similar to a shear
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