Need help with Rat

[warioblast]

Hi,
I put a Rat on my breadboard. I used tonepad schematic, and made some substitutions:
_ 100R instead of 47R
_ LM741     "        LM308
_ 2n5457    "        2n5458
Though it sounds good; close to the samples from Proco's site; I have an octave down sound when I roll off the volume of my guitar, and that when the drive control reaches half of its travel. Is there a way to fix this phenomenon ? Is the LM741 chip guilty ?
Thx for the support.
Cheers,
Fabrice

[oldrocker]

I just built a Rat a few weeks ago and I used a 741 and a MPF 102.  It works perfect with these trannys.  So I don't think the problem is that although if you socketed them then it wouldn't hurt to try some different combinations.

[warioblast]

I've done nearly everything I could.
I tried a JRC4558, but it was all the same. I checked my resistors, replaced the FET, replaced the pots, replaced the jacks, tweaked caps.... I took all the components off the breadboard, and tried another layout...
and still have that octave down sound 
I've just put a RM Mongoose on the breadboard; using the LM741; and the octave is here again, no matter how I crank my amp up.