[sdiy] The PPPPPulser

[Michael Ruberto]

Very cool Ian! it is interesting to watch the waveform start out as a simple 
pulse and evolve into a more dense series of pulses and eventually turn into 
a pulse with 5 peaks in it. it sounds pretty neat too.
I noticed that the DC offset varies quite a bit during the sweep. if a 
comparator is generating the output then what is causing the offset to 
change?

~M


>From: Ian Fritz <ijfritz at earthlink.net>
>To: synth-diy at dropmix.xs4all.nl
>Subject: [sdiy] The PPPPPulser
>Date: Sun, 08 Jun 2003 13:14:59 -0600
>
>Hi All --
>
>I took an hour yesterday and white-boarded the variable multi pulser I 
>proposed a while ago.  To review, it uses an LM3914 bar graph chip with a 
>constant (0-1V) saw drive and a variable (5-.5V) control drive on the 
>comparitor resistor chain.  The odd-numbered 3914 outputs are summed into a 
>comparitor to make a pulse train. The output starts out as a square wave 
>and continuously adds more pulses, up to five, as the external CV varies 
>from 0 to 5V.  The whole circuit just takes the 3914 and two op amps.
>
>The results are pretty interesting, I think.  The unit actually has a lot 
>of the characteristics of a filter.  There is a lot of phase shifting going 
>on, along with large and rapid changes in the harmonic content.  A sweep 
>through control voltages sounds somewhat similar to a sweep of a high-Q 
>bandpass filter.  Here's an MP3 demo, which is just a sweep up and down in 
>CV, with no other processing.
>http://home.earthlink.net/~ijfritz/xfer.htm
>
>
>   Ian
>

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