ultra flanger distortion

[65gmcjnew]

Hi all,  I've been lurking for a while, and can usually find an answer by searching,  but I've hit an roadblock with my ultra flanger.  I built it stock, using the pcb layout at GEOFX.  All voltages are very close to what is posted in the schematic. I am running of a power supply that puts out 9.35v, I did add tr3 and changed r 15 & 16 it sounds best at 5v,  voltage at the junction of r17 and led1 is 3.9v.  I've tried swapping all IC's with only some moderate improvement (right now a lm358 in u1, and a tlo22 in u5 replacing the others caused no performance change).  Also tried a 12v supply into a 9v regulated circuit without any success(in an attempt to get my voltages even closer to spec) . The distortion cleans up a little when I back off on the guitar volume or lighten my pick attack, but it is still there.  Any way to tell if I'm getting too much of a gain boost at u1a? Would it be beneficial to replace led 1,2 and d3 with a 3.9v zener? Any suggestions/thoughts?  Thanks  Jeff

[65gmcjnew]

still no joy yet,  I got the parts today to sub in the zener. I will give an update on that later.  Any other ideas?  Thanks  Jeff

[65gmcjnew]

well the zener didn't help, I wasn't sure that it would. I tried upping r5 to 18k, that didn't help. I also messed with r12, no joy. I jumpered d1 &d2 that got rid of the distortion, and most of the flange so I undid that.  I'm wondering bout r8? At this point I am guessing.. anyone...anyone   Thanks Jeff

[Fender3D]

Hi,
What kind of distortion is it?
cross-over distortion or clipping?

BBD's pin4 shouldn't be straight to GND, according to datasheet it should be Vdd + 1V, sure it will have some kind of tolerance, but I guess connecting it to GND might lead to issues...
Then the guitar signal is amplificated by R4/R2 = 1,5x.
I guess an input buffer and a recovery mixing stage at output should be a better solution...
All in all, surely a low-count-parts flanger, I wonder if it plays as good...

You could try with 12 or even 15 V, maybe, increasing headroom and see if it lessen distortion

[65gmcjnew]

Thanks for the reply. I believe it is clipping distortion. I did try 12v with no luck. I upped r2 to 330k and that has helped. I found another issue that might lead to the root cause. R12 & r13 are supposed to form a passive mixer. I just changed them to 4.7k each to the outside lugs of a 10k pot with the wiper to the previous junction of those resistors (from mods Mark Hammer suggested in another post).  I found I am not getting any dry signal. More trouble shooting to come. Thanks. Jeff

[Fender3D]

If you raise R2, then you should have a recovering stage at output...
About your other questions:
"replace led 1,2 and d3 with a 3.9v zener" will only change the sweep behaviour if resulting voltage isn't the same as L1+L2+D3, it has nothing to do with distortion

"I jumpered d1 &d2 that got rid of the distortion", you might take 'em off as well since bias is provided by U1.
it should work almost the same, thus avoiding diodes clipping, but if you have 450mV pick-ups you shouldn't be concerned about distortion...