AudioGuru, did you ever build this circuit? do you know what should be present on the cathode of D1? i was expecting a steady D.C voltage that rose as the frequency at the input of the circuit increased? but i am getting a rising D.C voltage with what looks like a waveform attached to it, or it might just be crud, i'm not sure. i'm not quite ready to give up on this circuit yet, but i have seen others that i want to try, my end requirement is a circuit that will flash lights to music divided into 3 channels, bass, middle and treble.
Terry.