[sdiy] Okay, I give up :-)

[Scott Gravenhorst]

Nicolai Czempin <nicolai.czempin at alcatel.de> wrote:
>Okay, I'll build the 4069 circuit. I cannot hold out any longer.
>It has been mentioned that parts can be left out.
>So, do I just leave out the whole "current sink" part and connect the CV 
>directly?

No, this won't work.  The circuit wants a current sink to ground.  You
cannot voltage control this circuit without either the 2 transistor (or
other design) expo current sink in the original drawing or the linear
current sink that I used in place of it.  They current sink type needs to
match the CV type for the CV to make a sensible musical scale.

>Can I leave out the "pulsewidth modulator" part if I'm happy with just 
>the saw out for the moment?

Yes, and it can easily be added later.  PAY ATTENTION TO THE PINOUTS IN
THE DRAWINGS.  If you deviate from that (as I did at first) you could have
problems, especially in the PWM section, should you decide to add it.

Note that if you add the PWM, the circuit will have 2 outputs.  One is the
saw out and is not affected by PWM, the other is the PWM output which is a
pulse where the width is controlled by the PWM CV.

>Do I have to keep anything in particular in mind when cementing the 
>transistors together?

Flat side to flat side.  Good thermal contact.

>What do I do with the "pwm" connection? I'd guess some kind of voltage, 
>but can I just ignore it initially?

If you build the PWM part, the input is a control voltage.  That voltage
controls the pulse width of the PWM output and makes a nice voltage
controllable timbre.  A cool sound when driven by a slow LFO, or you can
plug an envelope generator into it or whatever you imagine, even an audio
signal to get some weird sounds.


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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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