[sdiy] RE: [AH] A question about voltage controlled oscillators.

[Grant Richter]

Hi Alex,

Pin 5 is supposed to be at Vs/2 or 1/2 of 9 volts (4.5 volts). You can use
two 10K resistors in series connected between +9 and ground (battery -). the
middle of the two resistors will be at 4.5 volts. Connect that to pin 5.

If you want the waveforms to go +/- from ground then connect the ground ring
of your output jacks to pin 5 also. If the ground ring is connected to
battery minus, then the waveforms will always be positive relative to the
ground ring.

> From: Alex Dickey <Alex at centricitysoftware.com>
> Reply-To: owner-synth-diy at node12b53.a2000.nl
> Date: Mon, 16 Apr 2001 15:45:54 -0700
> To: "'Alex Le F'" <alex at cgfarm.demon.co.uk>, "synth DIY
> (E-mail)"<synth-diy at node12b53.a2000.nl>
> Subject: [sdiy] RE: [AH] A question about voltage controlled oscillators.
> 
> 
>> Is it possible to build very simple (one or two opamps, a few
>> resistors,
>> a few capacitors, diode, transistor...) VCOs that will output up to
>> audible frequency, or... not?
> 
> check this datasheet out:
> http://www.fairchildsemi.com/ds/RC/RC4558.pdf
> (oscillator's on page 8)
> 
> but i'm having problems getting this to work.  i think part of it is that
> i'm probably mixing up my Vs' and Vc's.  can anybody shed some light here?
> i was powering this using a 9v on a clip, and i had + from the battery going
> to both pin 8 and pin 5, - from the battery going to pin 4, and then Vc and
> the outputs going to jacks, with the jack grounds tied together.
> 
> can anyone see where i went wrong?
> 
> thanks,
> alex
>