OP AMP BAZZ FUSS !

[allesz]

After working on tube amps (with mixed results  ) and doing little builds here and there, I just started breadboarding again.
My plans are to get back experimenting with bbds, but I decided to start from simple things before attempting more ambitious projects.

Yesterday night I could not sleep and, thinking about future diy guitar electronic plans, I started to wonder if anybody ever tried a bazz fuss circuit with op amps... then I decided to wake up and give it a try.

It worked at first try - but -I only tried a UA741 single chip. I also got some TL071 to try out.

It's the same parts count as the bazz fuss! And it sounds good (a lot of things to tweak, of course)

You can also bias pin 3 of the IC at 1/2 supply power (tried resistors from 33K to 2,2M) and it works, of course, with more output and a different sound; I have to experiment a little, but it can be a nice way to control the bass content. Without biasing it gets a little bit less fat and more overdrivey than fuzzy... like 'em both.

I tried 1n34a germanium diode (little volume and little distortion), a couple of different leds (nice), but the plain old 1n4148 was just perfect; A couple of back to back diodes was not so interesting to me...

Have fun on your breadboard mates.

[allesz]

...ok, the TL071 didn't work
Tried the trick of biasing the non inverting pin, got a little bit better (didn't tried to ground it...), but went back  to ua741.

I think I have a couple lm 308 around... need datasheet.

[GibsonGM]

Search engine is your friend, Allesz!!   http://www.mit.edu/~6.301/LM108.pdf

Have fun fussing 

[anotherjim]

If you want simple ground bias, try a CMOS opamp. If you just tie +in to 0v, it shouldn't lock up a CMOS.

[allesz]

I thought lm308 had different pin connection... it's the same apart theneed of the slew rare cap (I don't have33pf, smaller value in my stash is 47).

Gimme some names Jim, it'really just a joke not a real project, but since it takes so little time I would not mind going on a little more.

[anotherjim]

CA3130, 3140.
Any TLCxxx
Any LMCxxx

Bi-polar LM358 can work, but probably gates due to input offset error. The right value resistor from +in to 0v can help cure that.
A while back, we got a simple comparator fuzz going with 0v input reference using a TLC272.

[duck_arse]

can I ask - what voltage do you get at pin 6 on the OP circuit? how does that voltage vary with differing part numbers, with pin 3  unterminated?

two 68pF in series will be 34pF, but 47 should be close enough for the jazz we are dealing in here.

[allesz]

I will report as soon as possible.
After this I put on on a sort of germanium fuzz, in the lines of the mkIi and... it's noisy (I don't have good germs)
but it sounds so good that a) I can't remove it from the breadboard b) I am thinking about a box to put it in... I shoul have some so and so pedal to sacrifice