VCOs for home-built modulars - update
mr808 at teleport.com
Fri Sep 1 02:22:56 CEST 1995
On Thu, 31 Aug 1995 gstopp at fibermux.com wrote:
> Oh cool you have a Chroma cuz I'm curious - what would you estimate
> the lowest possible VCO frequency to be?
I'll hook it up to the ole'scope this weekend to figure out what's going
on on the low & high ends.
> Yah yer right even if the saw gets a flat spot around 15 khz the first
> possible harmonic is 30 khz so really it shouldn't matter spectrally.
> I concede that I probably sound like a waveform snob and should tell
> everybody that if I give the impression that I think that any machine
> is less expressive than any other that's not my intention nor belief.
I think that the lower harmonics have about the same energy as an
undistorted saw - up past the 3rd harmonic (somewhere around 50kHz), I
don't think it matters...
> I can't back this up but I think that human perception goes beyond
The easiest way to prove it is to get someone to tell the difference
between a 15kHz sine & triangle - most people can.
> Maybe it's just a tingle at the back of the neck or something
> that bypasses the ears but I swear there's something up there. If I
> frequency modulate one VCO with another and start hypersonic and come
> down, as I pass through the limit of hearing there are some wheeps and
> squeals that I can only get on modulars with good-lookin waveforms.
Ok, I know what you're talking about...w/ filters that can go ultrasonic,
my ears feel like they're turning inside out on an upward sweep,
whereas if they're band limited (typical of digital anti-alias
filters), things just kinda disappear.
> I'm not sure how such things can make their way out of the
> reproduction system and into the air waves in the first place. Maybe
> it's some interaction that happens way up and I'm hearing the
> artifacts that splash down into the audible region. Anybody have any
> thoughts in this area?
Part of perceiving ultrasonics involves hearing the beat frequencies
generated by ultrasonics interacting w/ other frequencies. Of course a
lot of the digital crowd denies that this is either possible or
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