Hi,
just built this kit, and the sound level is very low, can only be heard if putting the ear right down to the speaker. Scope measurements seem to indicate that all three oscillators are running as intended, and the very low volume seems to be coming from the fact that the C2 100nF output capacitor is driving a 8R speaker - how can this in any way work? Even if C2 was MUCH larger, the 74HC14 only has 4mA drive capability - nowhere near enough to drive a 8R speaker with any sort of volume. Is there something I’m misunderstanding? Has anybody built this and is getting hearable output?
Just to prove my point, I disconnected the speaker and connected the output directly to my stereo amplifier line input, and the sound is fine. As soon as I connect the mini speaker it basically shorts the output coming through C2 to ground and both stereo (and the tiny speaker) go silent.