I’m looking for constructive feedback on a circuit. It’s quite straightforward, I think, however I’m still new to this side of things and I know I could be making mistakes in the design that I’m not yet aware of.
Further context that's not crucial to any response, but which may still be of interest
A friend recently asked me if I had any gear to sell, as he’s looking to expand his selection for a planned recording session. I told him that I didn’t but would he be interested in something built for him? He said he would, and I mentioned that a 4093 gated oscillator might be in his wheelhouse. He was interested, so I told him I could probably throw something together for him. And here we are.
Here’s what I put together as a reference in KiCad:
The goal is essentially to build a small tabletop noise box powered by a 9v battery.
It’s the gated oscillator circuit I saw here but I’ve added On-Off-On switches to add some variety to the ranges available and LEDs to give some visual feedback. I also added voltage followers between each of the triggers using an LMN324N (I got that from its datasheet). I’ve breadboarded the circuit and it works fine.
I’m not sure, though, if it makes more sense to only have a voltage follower after the final gate, and use the other op amps for something else.
Any suggestions, feedback, etc is/are humbly requested
Regarding the voltage followers: Maximum output current for the CD4093 per the datasheet seems to be around 3 mA. With 9 V power and a 1k resistor the current through one of the LEDs would be about 7 mA. So I’d say yes, if you want LEDs, you need the voltage followers at each stage.
You might want to add a small fixed resistor in series with each pot. As it is, at one end of travel the output of the CD4093 is connected directly to the second input, which would make it behave in an undefined manner, I think. I mean, maybe the behavior is something you like? But adding the resistor would establish a maximum frequency and keep it behaving normally.
Good practice, though you might not notice any improvement by them, would be to add:
100 nF bypass capacitors from each power pin on each IC to ground, located close to each IC.
A 10 µF cap from the power rail to ground would not be a bad idea too.
1k resistor in series between the final voltage follower and the output jack.
Your screen grab is kind of low resolution, I’m not certain of some of the text. Are C1 and C2 10 µF and 1 µF? If so then switching C2 in and out changes the total capacitance from 10 µF to 11 µF, only a 10% change. If that’s what you want, fine, but I think if it were me I’d want a larger change than that.
Yep that’s what I’ve got there, and you’re right, that’s not a huge change, at all. I hadn’t really considered it, tbh, so I may try a few different values to see how it sounds.
I appreciate the suggestions, @analogoutput and will likely incorporate them all
Yeah! Those are the words I couldn’t seem to find. Although I didn’t consider that it would probably be a much more dynamic change than I imagined due to each oscillator gating the next in the chain.
I’ve made versions of this powered with a solar panel and it makes some interesting sounds when it’s underpowered, so I think it could be a good addition.
Cool! I saw several demo videos for chaos nand diy projects when I started out a couple years ago and I thought the power starve was a cool feature. They were all toggled switches though.
Cool! I saw several demo videos for chaos nand diy projects when I started out a couple years ago and I thought the power starve was a cool feature. They were all toggled switches though.
I’ve been thinking about this a little bit this morning and last night. Could you accomplish the same or similar effect (i.e. a power starve) with a pot and a resistor as a voltage divider? Is there any advantage to using a transistor instead? Tbh, I’m not sure how I’d wire that up.
To be honest I’m not sure. The first thing in my thought was the chaos nand power starve with a simple switch. Sam (LMNC) uses a power starve to modulate overall pitch on his reverse avalanche mega drones. But the circuit closest to what I was thinking of is probably this part of Moritz Klein’s hihat schematic:
I’m not familiar with the engineering and math or anything from the datasheet for the 4093 so I couldn’t tell you if this implementation would work as it is meant for the 40106. Also didn’t remember the opamp part. As far as why the transistor instead of just the voltage divider I don’t know, but this was the circuit that inspired my suggestion I’m sure. Also Sam used a voltage divider on the mega drones.
According to his video the opamp is only to mix a cv input to function properly. He demonstrates how to do it without the opamp for his circuit, however as I said it is for a 40106. From Moritz Klein’s hihat video:
I watched that part of the video again and pay closer attention to what he was talking about and it turns out the transistor has to do with the input impedance being unstable throughout the sweep of the potentiometer without it as an emitter follower.
I’m worried that I’ve misunderstood how the SPDT on-off-on switch is arranged: my thinking was that each position of the switch would give you a different capacitor value. I think what I’ve done here is just put an off switch in the middle of each Schmitt Trigger.
No, the switches are fine. They put one or another capacitor, or nothing, in parallel with the unswitched capacitor, resulting in increasing, or not, the total capacitance.
