Phase 45 troubles

[RicF]

I just breadboarded an MXR phase 45 (tonepad schematic) and I can't get anything out of it. I hooked a resistor and led to the speed pot as a rate indicator, and it seems to be working just fine (blink blink blink, changes as I change the speed), but no sound passes through.  I'm not sure how to debug it; I really don't understand how the circuit works (never stopped me before) so I don't know what affects what. I used the parts I had on hand, a pair of TL072 op amps and 5458 FETs, with no attempt at matching them. Would mismatched jfets cause zero sound output? Any suggestions on probing for problems?

[Paul Marossy]

Would mismatched jfets cause zero sound output?

What JFETs did you use?

[RicF]

I used 2N5458s for the JFETS. I only have 4 of them and haven't tried swapping them out to see if it makes a difference. I kind of expected that if they weren't matched I'd just get a not-so-pronounced effect, but I'd still here some sound.  But I don't know if that's true or not.

[Paul Marossy]

I kind of expected that if they weren't matched I'd just get a not-so-pronounced effect, but I'd still here some sound.

That is my understanding as well. I would look for a missed/wrong connection somewhere. And, of course, an audio probe is an invaluable tool in these kinds of situations.