[sdiy] my VCO OSCILLATING!

[Jeff Farr]

Hey!  This is great news, I'm preparing a very similar circuit for the
OB1 clone!

On 12/10/05, Michael Ruberto <frankentron at hotmail.com> wrote:
> Whoa!!! I just hooked the output to speakers. This is one FAT PIG BEAST of a
> VCO!!! It makes my old ASM1 type VCOs sound anemic. Holy ground shakers
> Batman!
> Comparing with some samples of an actual SEM it has the same dry character
> but mine seems a bit brighter and has a bit more "edge" to it. Most likely
> the recording had the life MP3ed out of it.
>
> On the scope the waveform has an exponential curve to it's slope prior to U3
> and a rounded log type slope from U3s output. Tri and Sine waves are all
> messed up but I haven't touched the trimmers for the shaping circuits yet.
> Although, the messed up waves do sound kinda cool.
>
> I connected a perfect 1 volt ramp from my Tektronix Test Display Generator
> to the CV input and I'm not quite getting an octave. When I get done
> drooling over what's coming from the speakers I'll attempt to adjust the
> tracking again. Droooooooollllll....
>
> M. A. Ruberto
>
>
> >From: "Michael Ruberto" <frankentron at hotmail.com>
> >To: synth-diy at dropmix.xs4all.nl
> >Subject: [sdiy] my VCO OSCILLATING!
> >Date: Sat, 10 Dec 2005 00:41:16 -0500
> >
> >Sometimes if you stare and make threatening faces long enough analog
> >circuits start to work. But not this time. Like Tim pointed out there was
> >an error in the original schemo that I didn't catch. However, following
> >that correction came a freaky streak of failed parts. On my work bench I
> >have a small graveyard of transistors. They were all brand new parts too.
> >
> >Anyway, The VCO is now making a nice glitch-free saw but the frequency
> >range is very low. The pitch knob is only giving me around 1 - 50 Hz. I
> >toyed with the trimmers for awhile but could only manage to reduce the
> >range even more. I'm too tired to figure out this issue tonight. I suspect
> >the 2SC1583. Some resistor values will probably have to change. That will
> >be tomorrows chore after I work on the car.
> >
> >M. A. Ruberto
> >
> >
>
>
>