[sdiy] Simple (?) sequencer mod for syncopation

[Tom Wiltshire]

On 5 Jun 2009, at 05:33, Aaron Lanterman wrote:

> On Jun 4, 2009, at 2:48 PM, David G. Dixon wrote:
>
>> Now, coupled with these thoughts, I have just been reading Allen  
>> Strange's
>> book, "Electronic Music: Systems, Techniques, and Controls (1972  
>> ed.)."  In
>> the excellent Chapter 6 on "Gating" (page 44) he talks about  
>> something
>> called "pulsed mixing."  In this technique, one takes a pulse  
>> wave, isolates
>> the positive and negative parts, and uses them separately to gate  
>> two VCAs
>> processing different signals, causing anything from a jarring  
>> "ping pong"
>> effect to a seamless blending of the two.  I find this very  
>> intriguing.
>
> Believe it or not, the Buchla 257 Dual Control Voltage Processor  
> uses this idea to CV crossfade of two signal. It has a high  
> frequency oscillator that controls two CMOS gates that gate each of  
> the signals alternately on and off, and then runs that through a  
> boatload of filtering. The pulse width of the high frequency  
> oscillator controls the amount of each signal that is mixed in.  
> It's really freaky. I'm seen things like that in AM transmitters  
> and such but that's the only place I recall seeing it in a synth  
> circuit.

What you're describing would be a PWM mixer, wouldn't it?

I remember seeing this technique described in one of R.M.Marston's  
old CMOS books, where he makes variables resistors / potentiometers  
out of 4066 switches.

T.