overdrive sounds like a fuzz

[acehobojoe]

I've been messing around on the son of screamer circuit, here : http://www.tdpri.com/forum/attachments/stomp-box/210161d1386772082-lovepedal-eternity-burst-son-screamer-jpg

and for some reason, I always get intense fuzziness from the op amp. it is not the diodes, because when removed you still here that square wave type crushing on the signal from the op amp clipping. the way it is now, I have a slight overdrive when the 500k is all the way down, and then when turned up halfway, the intense clipping happens.

don't know what to do, i've double checked the breadboarding, seems all good. I must be sending too much low frequency content into the op amp or something.

[GibsonGM]

What opamp are you using?  Are you running your guitar straight into this, or feeding it with a circuit before?

Could you have put some wrong value resistors in the feedback loop?  Check the values....R3 and R2....it shouldn't distort like this.  Could be something wrong with the opamp, but I have a feeling there may be a component of the wrong value or miswired...

[acehobojoe]

Yea, I think it is not the op amp. I have 4 jrc op amps and some LM whatevers, all of them act the same, let me check again the R values, I checked, and the one going to the end of the 500k pot is 47k, the other is 4.7k and that should be it.. :/

I'll keep looking

[acehobojoe]

redid it all, it's still fuzzy... let's see..

[GibsonGM]

Take a (DC) voltage reading at the + input, and also at the 'far end' of the 470K bias resistor....should be about 1/2 supply at that point....A badly misbiased *anything* can sound like you describe. If it's doing it with other opamps subbed in, this might be why.   

If the Vr checks out, please measure and post all the voltages on all the opamp pins.  Makes sure ground (pin 4) is actually grounded, and yuo get supply voltage at pin 8, too...

[acehobojoe]

I'll get back to you when I check them. thanks!