ETI Project 447 Audio Phaser

EDIT 2014-10-20
I added a soundclip. Notes: for this clip I had increased the 15K resistor (to the right of IC4) to 33K to lower the effect depth (I found it too wobbly), and I increased the 33K resistor to 47K to keep unity gain. This is as fast as this phaser goes, so it would probably be a good idea to mod the LFO secion aswell to increase the range. The wave-shape could also be better... but this is how it is without too much changes to the original schematic.

DIY phaser from ETI.

When I first built it up it was super noisy, so I modded it to reduce the voltage divider before the first phasing stage and I also reduced the makeup gain of the last transistor. Now it's totally usable, however a drawback of the mod is that there can be some minor distortion if you are using hot humbuckers.

It's important to set the Bias trimmer just right. It has a small area where phasing occurs and it controls the waveshape of the sweep aswell.

There are a couple of other things to notice.
When I drew up the layout I mistook the Bias pot for a Depth pot.. I don't wanna add the trimmer to the board, because it would mean even more cuts, links and possible a larger board (now it fits perfectly in a 1590BB). so, you will have to put the Bias trimmer on a separate small piece of vero.

The last thing is that it needs a 100K resistor from the output to ground, otherwise it will pop when switching to bypass (the original didn't have true bypass). It is easily soldered directly to the 3PDT switch.