I just built Serendipity and when I use OPA2604AP the effect was working but with some fuzziness so
I swap with njm4558D and tlc2272cp and I have no sound.
I measured my ic voltages and everything works fine.
Does anyone experience the same problem?
Do you think I used wrong Ic ?
Finally I solved it I forgot to connect the opamp loop pin6 and 7 thats why only OP275 and OPA2604 worked wiht fuzziness.
Always double check your solder joints.