follow up regarding the threshold circuit, fets etc.
I just spent the last couple of hours playing with the threshold circuit whilst monitoring the waveforms on the scope.
I retained the 100k linear threshold pot (I just could not get the range from a 10k pot).
With the threshold control fully clockwise it is efectively out of the circuit and consequently the fet is turned hard off.
With this setting and a socket for the fet on the board, I tried a range of n channel jfets that I had stock of. None of the different fets tried had any effect on this setting ( I was comparing to no fet at all in the socket

). However, when I turned the threshold control fully counter clockwise the differences were astounding (well interesting perhaps).
First up the J201 - hardly any difference at all from fully clockwise - not suitable

Next The 2SK117 - slight attenuaton - again not suitable
Then the MPF102 - hardly any attenuation - not suitable
Then the 2SK30 - again not suitable
Then the 2N5457 - very slight attenuation - not suitable
Then the 2N5459 - aha approximately 30% attenuation - looks promising......
BUT when I installed the 2N3819 I got maximum 50% attenuation - ideal - I tried a few more and they all worked fine.
I must get the correct fet LS4393 (or 2N4393) and try it, but for now the 2N3819 works as it should and almost completely attenuates the BBD output leaving just the dry signal.
One interesting discovery along the way - the best flanging effect occurs when the dry and delayed signals are the same intensity. After adding the 22k resistor as I suggested in my earlier post it is neccessary to adjust the trim pot on the output of the BBD (shown as simply TR on moosapotamus schematic) to obtain the same level of delayed signal as the dry signal - this is easy to see on the scope - just set the range control fully counterclockwise and use the manual control to sweep up and down - you will see the delayed signal collapse as you turn the threshold control fully counterclockwise - take a note of the dry signal level. Now turn the threshold control to full clockwise and adjust the trim pot TR until the signal level is now twice the dry level - you may have to sweep the manual control to give a clear picture on the scope.
Try these suggestions and you WILL get a whole range of very usable and satisfying sounds from this Flanger design - On the other hand tweak away in the darkness and you may get some meaningful sounds from within the chaos. Seriously - unless you have a scope and a good digital mulimeter with a frequency counter function on it you are never going to hear the GREAT sound this baby is capable of giving you.

Cheers
bajaman