synth

I'm trying to make a VCO from this schematic but I can't get it to work. My oscilloscope broke so I can't use it but when I plug in my headphones I only hear a slight DC voltage. (The circuit runs on a single supply)

Hey! So I've been trying to build a modular synth on/off for the last year or so, and one of the most simple projects I thought I should start with is a mixer circuit. I found a really simple circuit schematic and shortly after got it working on breadboard, with absolutely no problem at all...

Hi everybody !! Well, I recently made the famous LM358-based VCO as in this article : https://www.allaboutcircuits.com/projects/diy-synth-series-vco/ Everything seems to work fine except those buffers which I can't get to work at all and I just can't understand why ... I've already tried...