[sdiy] Re: Spiral Waveforms

[Scott Gravenhorst]

First, I think that everyone was caught off guard by Steven.  No one knew
until days later why he responded the way he did.  After reading about AS,
his posts make more psychological sense.  I doubt the group reaction would
have been as it was had we known, I don't believe that anyone here is
intentionally cruel.

That said, here are my random synapse firings...

Ian's description notes that a constant angular velocity yeilds a constant
output frequency, which is a good thing for tonal music.  But this doesn't
seem all that easy to do in analog electronics.  Sawtooth and triangle
oscillators try to do this by using a linear current to charge a capacitor.
 The sawtooth has the nasty reset time that perturbs constant angular
velocity.  I'm not sure, but triangle oscillators may also exhibit this to
a lesser degree at ramp direction reversal time due to the finite amount of
time it takes to switch the current source's polarity.  Once we get away
from linear ramps, things get difficult.  Someone correct me if I am wrong,
but sinewave oscillators don't operate by following a dot as it goes around
a circle with constant angular velocity.  Of the difficulties involved, it
seems to me that there are two main requirements: 1) a circuit to establish
and maintain the spiral and 2) a circuit that can provide a projection of
the spiral placing a "light source" at a given angle.  One way to approach
this might be the use of quadrature, would simple panning provide the
projection?  If one distorts the quadrature outputs, the angular velocity
is maintained, but would panning still give a (variable) projection?  It
seems that this idea might be more easily implemented using DSP or other
digitally computed methods.  I can't envision how much different this would
be from what we already do with oscillators and waveshapers.



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