Post by keurslagerkurt on Feb 8, 2021 23:10:45 GMT
Hi all!
So I found this old electrosmash thread about 'the simplest vca', and more specifically this schematic:
Its apparantly taken from a Roland DR-110 drum machine. As is, the circuit only lets through the positive half of the audio wave, but I thought this might not be a problem at all for AE (only positives!). I breadboarded it, even omitting ALL capacitors and R1. I used a standard NPN transistor, an 1N4148 diode and a 22K resistor for R2. It seems to work... on some inputs. Especially on the squarewaves it works nice, I guess because they are so LOUD and act as ON-OFF for the transistor? Still, a fun 3-part VCA for square waves, with a bit of waveshaping involved too.
For the other waves, it really depends on the volume it seems? But it also seems do depend on the pitch, lower pitches worked better for me. Seems kinda weird and I don't get it. I've been simulating it afterwards, and I think together with C1 of like 1uF and R1 of 1M to 2.5V this circuit should work on the less loud waves too. But I still have to test that!
Anyway, does anyone have a clue what C2 and C3 are for in the diagram? I seem to get better results without them, and I tried a LOT of values for them, both in simulation and on the breadboard. And I also tried to tie them both to ground and virtual ground.
And another question: shouldn't there be a resistor from the emitter of the transistor to ground? Or is it no problem that the base current gets shorted?
So I found this old electrosmash thread about 'the simplest vca', and more specifically this schematic:
Its apparantly taken from a Roland DR-110 drum machine. As is, the circuit only lets through the positive half of the audio wave, but I thought this might not be a problem at all for AE (only positives!). I breadboarded it, even omitting ALL capacitors and R1. I used a standard NPN transistor, an 1N4148 diode and a 22K resistor for R2. It seems to work... on some inputs. Especially on the squarewaves it works nice, I guess because they are so LOUD and act as ON-OFF for the transistor? Still, a fun 3-part VCA for square waves, with a bit of waveshaping involved too.
For the other waves, it really depends on the volume it seems? But it also seems do depend on the pitch, lower pitches worked better for me. Seems kinda weird and I don't get it. I've been simulating it afterwards, and I think together with C1 of like 1uF and R1 of 1M to 2.5V this circuit should work on the less loud waves too. But I still have to test that!
Anyway, does anyone have a clue what C2 and C3 are for in the diagram? I seem to get better results without them, and I tried a LOT of values for them, both in simulation and on the breadboard. And I also tried to tie them both to ground and virtual ground.
And another question: shouldn't there be a resistor from the emitter of the transistor to ground? Or is it no problem that the base current gets shorted?
