Neovibe staticy breakover distortion... audio probe results!... R.G.?

[DeeBug]

Hi R.G. (and anyone else who can help), I finally got round to building an audio probe and doing what you suggested back in April.  I put a link to that earlier thread at the bottom of this post.

To recap the April thread, my Neovibe does vibe now (it was the perennial "speed pot wiring" problem), except that there's still a "breaking over the edge" distortion problem.  I can hear the effect real well.  It would sound fantastic except for that static-y sounding breakover (by the way, there's no problem in bypass mode).  Problem is worse with a LP than a Strat, though still bad with my single coil Strat.

I think that from here on you'll need to use an audio probe to figure out exactly which stage is doing the breakover. Probe the collector and emitter of Q3, 5, 7, and 9, and the emitter of Q10, listening for the first stage where you hear the breakover. You will have to use a capacitor-isolated probe.

Here are the results of my probing with the audio probe.  These results were obtained by strumming on the open D and G strings of a Strat through a clean SF Princeton amp.  When I tried the same thing with an LP, the results were far more pronounced.  I wanted to make sure none of the breakup was caused by the LP, so I used only the Strat results.

Q3 - collector: substantial static-y breakover with some fuzziness to it
Q3 - emittor: slightly less loud than Q3c, but clean.  The cleanest of all the points I tested.

Q5 - collector: breakover, but a bit less than Q3c
Q5 - emittor: very, very ratty breakover, sounds pretty bad

Q7 - collector: some breakover, about the same as Q5c
Q7 - emittor: similar to Q7c, but rattier (though not as ratty as Q5e)

Q9 - collector: some breakover, about the same as Q5c and Q7c
Q9 - emittor: fairly louder than Q9c and much rattier breakover (somewhere in between Q5e and Q7e in terms of "rattiness")

Q10 - emittor: breakover, much like Q3c

So, to sum up:
Q3c, Q5c, Q7c, Q9c and Q10e all have breakover noise
Q5e, Q7e and Q9e all have a dirtier, rattier, nastier breakover, with Q5e being the worst
Q3e is pretty much clean (at least with the Strat it was)


Does this give you any ideas what might be going on?  It'll be great to finally figure this out and get a nice clean sound.  The effect itself sounds amazing.  Thanks in advance!

Link to April thread:
http://www.diystompboxes.com/smfforum/index.php?PHPSESSID=d7f5a0505a23231bea3004216e6cf267&topic=44547.0

[DeeBug]

OK, after months of head scratching, I've finally figured it out. 

The probe results led me to take a closer look at the caps in the area where the noise was.  I noticed that C4 and C12 were marked 330J and 470J respectively.  Yet the Mouser baggie for these caps had them labeled as 330pF and 470pF when in fact they were 33pF and 47pF.  (Doh! Another dumb newbie mistake.)  Well, I subbed some ceramic caps of proper value (until I can get the proper polystyrene replacements) and the crackle was gone... problem finally solved!

Thanks again for all the help you gave me back in April, R.G., and I join the others on this board in thanking you for making this ultra-cool pedal available to us!  Cheers.

[R.G.]

Sorry I didn't reply sooner. I've been working the Visual Sound booth at summer NAMM.

Good work! Figuring it out from the evidence at hand, no matter how crypic, is always lots of work, but it makes you much better at what happens the next time.