Hello everyone!
I designated this schematic of an Oscillator Driver with PWM CV and 1v/oct CV, and also a Square Wave/Triangle Wave Lfo.
I used the synthforbreakfast.nl site as reference sources for the exponential current converter; for the lfo I saw on the MFOS website.
I was wondering if someone can check my schematic to see if anything is wrong. Any kind of help will be appreciated.
Thanks!
Hi,
On the first view the voltage follower U2B should connect the feedback to the negative input, and the Led should be connected to the connector, not the emitter.
You should add 2x 100n caps to the power rails of each tl07x.
The schematic shows only some different modules, where do you connect the lfo and 1v/oct out? From where do you get the pwm inputs?
For the rest I need a deeper (and longer) look.
Are input 1, 2 and 3 supposed to be 1V/oct inputs? If so, I’d give them a 1M input impedance, and buffer them separately. Then if the summing opamp is supposed to be a precision adder, the input resistors need to be matched. I’d probably also add a series resistor to the gain trimmer, to limit its range.
I had put 300K and 3M3 as values because SW2 has to select whether the pot tuning should be fine or coarse. How do you buffer them separately?
All of the input and output are connected to jack Sockets. Why does the led should be connected to collector?
For lighting the Led your transistor configuration can work, but it requires a much highet base Voltage than the common emitter config. If the led is connected to the collector you can control the led by just aplying >0.7v to the base. If its connected to the emitter you need a much higher voltage.
My question regarding the connection between lfo, pwm etc. Was how do you connect them toghter logically. The pwm part is at the moment only a buffered voltage. Where do need this voltage? There is no other label pwm output in your schematic, so this is not connected to the other parts. Same with lfo and 1v/oct out…
Sorry, I didn’t catched! These are connected to the tune CV and pwm cv input of my AS3340 oscillator (although I want to create an oscillator based on op-amp, maybe this makes more sense to use there). This project is more of an expander than a driver.
Ah ok, now I understand.
It shouldn’t be necessary to buffer inputs 1–3 separately; the right ends of the input resistors are connected to a virtual ground, so they won’t influence each other.
But I’m puzzled as to what the exponential converter is needed for. The AS3340 takes a linear input and does the exponential conversion internally. So what would this be used for?
Being the output of an exponential converter, the output labeled “1 V/oct” isn’t a 1 V/oct control voltage. The converter takes one or more 1 V/oct control voltages as inputs.
A point of schematic style: You have global labels on outputs like LFO Output, PMW Output, and 1 V/oct pointing toward the left, which implies they’re inputs. It would reduce confusion to reverse the label direction to point toward the right. (Change Input to Output in the label properties dialog.)
You understand, don’t you, that your tuning knob will give you either coarse or fine tuning, depending on the switch, but not both? If you switch to “fine” then whatever voltage was being provided for coarse tuning disappears and vice versa. It would be more typical to have separate pots for coarse and fine, and no switch.
For the PWM section, are you sure a voltage follower is what you want? That means the inputs are being averaged, not summed, and if it’s possible for PWCV and PWCV2 to be connected and disconnected then doing so will change the output amplitudes due to the other inputs. Or if whatever connects to PWCV or PWCV2 is low impedance then they might distort each other. If they’re fixed connections then maybe it’s all right.
Yes I know it’s a useless thing on the AS3340 but my goal is to create an oscillator that doesn’t have an exponential converter and that takes the CV from this module (in fact at the moment it will remain there as an expander).
Having fine tuning and coarse tuning selectable from the switch was what I wanted to achieve - good old fashioned moog modular driver boy. PWMs are not fixed connections, to solve the problem can I just buffer all the inputs separately?
Thanks for the tip on KiCad labeling, I thought there wasn’t a section to specify whether it’s an input or an output.
