insanity and the diode comp opamp

[sean k]

http://www.diystompboxes.com/analogalchemy/pedals/diodeopamp.html

http://www.diystompboxes.com/pedals/insanity.GIF

For some unknown reason I can't remember I decided to build the Insanity using the diode comp discrete opamp instead of one section of a 4558 or even a TLO71 which would have been far easier.I used the schematic for the opamp at the top of the page from the top link and just slotted it in to the insanity schematic where the opamp at the beginning goes.  It didn't work....
 
Eventually I kinda got it working by bypassing most of the opamp and injecting signal straight to the base of the 2N5089 and this showed me that all the insanity stuff was working fine and all my problems were due to the first two emitter linked PNP transistors.

Instead of going through the whole story I'll just let you know what I've changed so far to get a pretty neat sound going.

I'll go through things in the order I modified them.

First is the 470k reference for the plus input goes to ground and not to the 4.5 volts.Then remove the 100k, from the parallel emitters of the PNP transistors,that goes to the base of the 2N5089.Take the 1N914 diode out and replace with a germanium one and put back in the opposite way.Next take out the 10k resistor from collector to ground on Q2 and run straight to ground.Lastly remove the 1M pot and 220pf cap from the feedback loop and replace with 4.7M fixed resistor with 82pf cap bypassing it.All of this means you can't control gain anymore but all you have to do is remove the 100k trimmer after the diode clipping in the insanity schematic and replace with a 100k log pot.The 470 nano cap,over the 4.7k resistor to ground,in the feedback loop still goes to  the negative input.

Before I changed the diode and turned it around the clipping was round the wrong way or at least didn't work anyway I liked and was more like a gate.With the germanium in there it clips and sounds good.
http://sound.westhost.com/project07.htm

The schematic here was what put me in the right direction.

I haven't put it in a box yet so its kinda hissy but its an interesting kinda fuzzy distortion box.

All I can say now is the diode compression opamp didn't work for me,at all,but It was a steep learning curve learning how signal diodes actually work.