[sdiy] Hewlett-Packard Oscillator

[Donald Tillman]

[Subject line change, as the conversation has drifted somewhat from
the Taylor Series.  (!!!)]

   > From: Aaron Lanterman <lanterma at ece.gatech.edu>
   > Date: Fri, 5 Jun 2009 01:52:00 -0400
   > 
   > I remember Grant suggesting one that uses the weird properties of
   > an incandescent light bulb. (I believe it was the Hewlett-Packard
   > design.)

Not that weird... it's pretty well known that the resistance of metals
changes with temperature, right?  And this is 1939 technology.

The cool thing about the Hewlett-Packard oscillator is that you can
hear it (or a clone of it) at the beginning of Frank Zappa's "Return
of the Son of Monster Magnet", the last song on the first Mothers of
Invention album "Freak Out" (1966).

The clues are there if you listen closely... the oscillator is played
over the 20-200 Hz range, the 200-2000 range, and the 2K-20K range.
And each time he switches ranges, you can hear a little amplitude
"bounce" as the feedback loop stabilizes around the incandescent
lamp's thermal time constant.  This is a very unidentifiable
characteristic sound.  FZ notices it, and starts using the range
switch as a sort of percussion instrument.  And the oscillator is
overdubbed, so you can hear two of them going at it in a sort of
sci-fi counterpoint.

While listening to this it helps to visualize FZ working the
oscillator with both hands like a mad scientist, with his eyebrows
going up and down.

  -- Don

-- 
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com