Homebrew Drum Computer Delay Lines

Robert Nansel bnansel at bigpond.net.au
Sat Dec 15 18:34:11 CST 2007


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."

Magnetostrictive delay lines are attractive, though I hear they are  
more than a little microphonic.   I notice that most magnetostrictive  
delay line designs use the transducers to generate  torsional waves,  
which apparently suffer less from dispersion and have a slower  
propagation speed to boot. The pictures I've seen show the  
transductive materials spot welded to the delay wire such that they  
twist the wire when a magnetic pulse is applied:

http://www.science.uva.nl/faculteit/museum/delayline.html

Does anybody know how well plain nickel wire would work OK, or would  
some more exotic like Terfenol-D be required?  The delay wire itself  
need not be magnetostrictive; it's just the storage medium.

-Bobby



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