Thanks you for your reply. Much apreciated! In the datasheet of the 555, “Control Voltage Level and Threshold Voltage” @ 15V is given with 9 min and 11 max. Given your answer, I think I am correct in my understanding that this is not a min / max for the pin but rather gives the accuracy at this pin if nothing is connected to CV (as this is exactly the 2/3VCC ± tolerance).
I tried approaching this from how the 555 functions. To my knowledge (which might be wrong, as my electronics knowledge is weak), comparators do not like negative voltages at their inputs. Also, if CV is negative, this would have effects on current flowing from ground through the other two 5k resistors to the CV in pin. Not sure how the comparators would react to that. I think I will do some more thinking around that.
Where I am currently stuck is: If I have a VCC of 12V (or 9V in the case of Sam’s circuit) and inject a voltage at CV, how do they add? I know its very basic electronics but I can’t wrap my head around it. Do the voltages simply add up or do I need to use superposition (and if whith wat internal resistive values).
Thanks for you help, it allows me brushing up my knowledge.
Yoo guys just wanted to show off my AAAPPPCCC as a KOSMO module! I love this synth and I just converted the small 3.5mm inputs to 6.3mm ones. And I bypassed the output voltage divider that converts the around ±10V signal to headphone levels. I hope, the AC-coupled audio output is ok to the other modules!
Looking forward to connect this module to other modules (that I still need to build)
Nice optics 
I like the seamless mounting and jack conversion
The signal before the voltage divider is (or should be) 0 to +9 V, not ±10 V (assuming you’re still using +9 V power). That’s an okay synth level, 10 Vpp is kind of standard but 9V is close enough.
Thx for your advice…okay, since I power it from the standard +12V eurorack PSU port, the output is also 0 to +12V, right? But since the output is decoupled with a 10µF electrolyte cap, should I pull the output to GND with like 10kΩ to get a 6Vpp audio signal?
Most module inputs have some finite resistance to ground (100k is more or less standard), but occasionally one doesn’t. So I’d put a resistor to ground, yes. In fact I think I might make it 100k and change C7 to 1 µF but your 10 µF and 10k is probably fine.
Now it’s a module, have you considered applying some circuit bending adaptations to the A³P³C³?
(I got the AAAPPPCCC name but my dyslexia transcribes it in my brain to ‘Apollo’, it’s maddening)
Anyway…
Some bending ideas might be CV control of the power to starve it
or a range of caps and resistors on rotary or dip switches,
Perhaps add a Tone stack module with selectable circuit insert positions.
I would remove risk and isolate the output through an opamp you could power from your Kosmo supply.
Oh yeah circuit bending is a nice idea! Maybe I try the power starving thing soon! I already put audio through a power amp into one CV input (with like 8 Vpp) and there is a knob position combination, where you can hear the audio in a verryy distorted, crushed way at the output. Thats a very cool sound for hard drum and bass beats, if you ignore the screaming high frequency sounds. Didn’t got them out with an EQ or Notch-Filter unfortunately
Try using an additional filter to separate all but the high frequency sounds and then invert that signal and mix it back in cancelling out the hf audio.
The power amp use is cool; if you add say a microphone and an envelope follower you could use your voice or other sounds to shape / play your crushed effect.
Great stuff!
yooo thats a very cool idea! But isn’t that like using just a low-pass-filter? Anyway, I’ll try it out (with VCV Rack since I don’t have any other modules yet lol)
The effect is the same but a signal through a LPF, blocking the unwanted HF, the sound you get will still contain artifacts (harmonics) of the high frequency and this will affect perceived tone / timbre.
Whereas by mixing in (adding) the same but inverted high frequency you cancel out those artifacts in the sound related to the HF sound.
In short it’s just using an additive synth technique as a ‘different’ kind of filter and if I’m honest I doubt folks could notice the difference but as a piece adds more polyphony these artifacts will grow and colour the piece, which can be bad or great depending on your preference.
Try some experiments in VCV rack and see what you think.
Actually you might like to look at the SSM2000 chip. A stereo analogue noise reduction system with several built in methods including active noise cancelling. You can grab an SMD version for under £20 and as there are many ways to wire it as a dedicated noise reduction module or a analogue filter.
yeah ok xD I didn’t mean the experimenting this serious, but I add it to the module to do list. Since I am just starting with DIY modular, I still need to build a bunch of other modules
Hi all! So I finally made 2 AAAPPPCCCs! I made the first one and it was hardly working and was at a super low volume when it did make noise. I thought maybe I had a cap backwards by accident so I figured I’d hold off until I had time to put together the other one to see if it was any better. It was having the same issues. I had no problems when I made my CDODs. I’m wondering if I got some bunk chips? Maybe I have the wrong type of resistors on part of it? I’ll snap a pic when I get a chance so you can belittle my haggard build and possibly show me where I went wrong.
Hi everyone super basic question but total beginner putting together the components on the aaapppccc board but wondering what dc power plug I need to get hold of yo get this cranking am I looking for a 9v DC pin plug that fits the 2.1mm dc jack?
Such as this 2a 9v one?
Many thanks 