OTAs and Harry's flame bait BDDs

[Scott Gravenhorst]

"J. Larry Hendry" <jlarryh at iquest.net> wrote:
>----- Original Message ----- 
>From: Harry Bissell <harrybissell at prodigy.net>
>BTW I consider the BBD a digital delay, albeit
>a Sh!tty one. The fact that it has an analog range
>of oh... a couple volts in the Y axis does not cover
>up the sampled data nature of the X axis.... 
>so just saying analog does not mean good !
>
>(if this don't draw some flames then the list is dead....;^)
>H^) harry
>----
>ZZZZzzzzz.........
>You are witnessing the lingering effects of turkey induced tranquility.
>Larry H
>
>----- Original Message ----- 
>From: Scott Gravenhorst <music.maker at gte.net>
>An OTA (operational transconductance amplifier) is an
>extension of an opamp in that the multiplier is controllable 
>by a voltage.  Even more fun things can be done with an
>OTA,  including voltage controlled oscillators, filters and
>amplifiers (plus more).  
>----
>Forgive my ignorance as I am still a newbie to these synth circuits.  I
>am learning and am just getting a fairly decent handle on these
>op-amps.  My first real project was to use some 1013 op-amps
>to add octave and interval switches for any 1-volt-oct VCOs since
>the MOTM-300a that I use have only continuous tuning.
>
>The prototypes can be seen at:
>http://www.modglin.com/larry
>
>I found Scott's etire post to be quite interesting.  But, his description
>of OTA's is what has me most interested.  Seems like this might be a
>nice "next step" for me to build something.  I plan to do some
>reading in some of the recent texts I have acquired.  But, I consider
>this list a better resource than anything, so I will ask a basic question.
>Are OTAs really good choices for voltage controlled amplifiers for use
>in things like VC panners, VCAs amd VC mixers?  Or is purseing that
>course of action mostly an excercise in education?
>
>Is 3080 I see mentioned a lot a good choice for VCA applications?
>
>As always, thanks for the expertise, humor, and tolerance of newbies on 
>this great list.
>
>Larry Hendry

My first exposure to OTAs is the PAiA FatMan synth.  The VCF
and VCA are made with OTAs.  The VCF is a state variable type.
I've since built a triangle VCO and another VCF using OTAs.

Different filter designs can have different sounds and differing
responses to the control voltages fed them.  Beauty being in the
ear of the beholder, I would answer your question by suggesting 
listening to examples of different architectures.  OTAs can 
simplify things, but may not produce optimum results to the ear.

Like religion and politics, your milage may vary.

-- Scott Gravenhorst : On The Edge, but the Edge of What?
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