Need help with schematics...

[Cymastar]

Hey everyone.

I'm trying to make a pedal based off of Tim E.'s "Simple Square Wave" schematic, plus the addition of an "octave up" circuit, however, I'm having trouble figuring some things out...


As you can see, the circuit designed by Tim shows two transistors on the board with the notation "U1, U2 = Op Amp".


Matt Casey has used the TL072 op amp in this layout.

My question is, can I use other types of op amp? I have a JRC448D and an MC1458N already, and if I can use one of them, it would save me some cash.

Also, does anybody have any ideas for adding an octave-up onto this? More like the Jawari or Pushme Pullyou than a clean octave (I'm aware a clean octave up is impossible). I'd like to make it switchable/blendable.

Help would be much appreciated!

[Cymastar]

Maybe I could split the guitar signal and run the clean signal into the carrier input and the fuzz signal through the modulator?

[Quackzed]

the 4558 is the same pinout and will work, not sure but i believe either will work the same... if i were going to add an octave up in parallel
i'd start with an opamp buffer then split from the buffer to 1.the shaper 2. the octave up you choose. then wire the outs each to one side of a ppot for a blend... then to volume pot for overall volume.

[GibsonGM]

4558 will work, but is a higher-noise opamp.  The TL072 is just a better unit.

[Cymastar]

Would there be any benefit in changing the 25k trimpot to a 100k external pot?