Yes, actually. I got my first VCO board running on the bench
yesterday. I am building two of these, without the waveshaping
circuits. Mine only has the sawtooth and square outputs. It has coarse
and fine frequency pots, an FM input that switches between exponential
and linear, and a 1V/oct input. Also the sync and PWM inputs. I
changed a lot of the VC mixer resistor values, and also used an LT1013
op amp there. This fits in a 1U panel (still to be ordered from Front
Panel Express).
You would need another op amp (similar to the ASM-1 VCO) on the PWM
input if you wanted to add a PWM pot. There is no mixing on that input.
I do have a question for Ken. The sawtooth buffer amp shows a 330K
feedback resistor and a 240K bias on the schematic. I inserted pots and
adjusted to get a +/-5V sawtooth. The values turned out to be exactly
200K / 600K, just like the ASM-1. This is also just what you would
expect to convert the 0-5V signal out of the CA3140. Double the voltage
(200K/100K), then offset the 0 to -10V result back to +/-5. I think
maybe the 330K/240K values are for a +/-12V power supply.
-Richard Brewster
Bob wrote:
yesterday. I am building two of these, without the waveshaping
circuits. Mine only has the sawtooth and square outputs. It has coarse
and fine frequency pots, an FM input that switches between exponential
and linear, and a 1V/oct input. Also the sync and PWM inputs. I
changed a lot of the VC mixer resistor values, and also used an LT1013
op amp there. This fits in a 1U panel (still to be ordered from Front
Panel Express).
You would need another op amp (similar to the ASM-1 VCO) on the PWM
input if you wanted to add a PWM pot. There is no mixing on that input.
I do have a question for Ken. The sawtooth buffer amp shows a 330K
feedback resistor and a 240K bias on the schematic. I inserted pots and
adjusted to get a +/-5V sawtooth. The values turned out to be exactly
200K / 600K, just like the ASM-1. This is also just what you would
expect to convert the 0-5V signal out of the CA3140. Double the voltage
(200K/100K), then offset the 0 to -10V result back to +/-5. I think
maybe the 330K/240K values are for a +/-12V power supply.
-Richard Brewster
Bob wrote:
>So,
> has anyone got one of these VCO's up and running yet? I am really
>curious to hear the what people think about the waveshaper, sub osc
>features, and overall sound. I am working on making one up for my
>system, but I can't decide if I want to add the kitchen sink or just
>keep as a more basic vco... any thoughts would be helpful.
> one final thought, there is no pot for Pulse Width on the
>schematic, could that be added?
>
>thanks
>
>Howard
>
>http://www.bobknarley.com/synth.html
>
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