I was looking through my box of finished but not working projects this weekend (you all have a box like this don't you?) and found two(!) copies of the ETI six-stage audio phaser Project 447. I haven't a clue where I downloaded it from so I can't point you to it.
I am wondering if anyone has successfully completed this phaser. There is at least one error on the PCB layout with the bias trim pot connected to the wrong place. I've fixed this on both boards but I continue to get loud static no matter where the trimpot is adjusted.
The clock appears to be working and I get a faint (compared to the static) dry sound through it
This project uses a 4049 hex inverter as the variable resistance element. The auther claims that the inverters are complementary FETs and that the resistance can be controled by applying a voltage its gate. Can someone explain how this works? In the schematic all the inputs to the inverters are attached to the clock signal, the outputs go to each of the allpass stages and both Vcc and Vdd (and pin 16 which is marked "no connection" on the data sheet) are connected to Vref (which in this case isn't exactly half of 9 volts, it uses a 10k/15k reference). Does this make sense?