Blue Box tip from the past

[Mark Hammer]

I had boxed up a Blue Box clone, using the Tonepad board, and it was misbehaving.  The Blue Box is not exactly the best-behaved pedal even when it works according to plan, but this one needed to be sent to its room.

Searching through my hard drive, I stumbled across a contribution from 2003 by a forum member who simply went by the name Stewart, who notes:

Check out the blue box schematichttp://www.compassnet.com/~cjlandry/schems/bluebox.jpg
and also the crash sync circuithttp://www.hollis.co.uk/john/crashsync.jpg
The two circuits have the same front end, except that the crash sync has an additional resistor (1 meg)
between 9Volts and the invert input on the second opamp. This pulls the invert input back up to 9V,
which will gate off the sound. If you add this resistor to the blue box schematic then it will gate better.
If you reduce the size of that resistor then it will gate quicker. I put a 330K resistor in mine and it
gates OK. Or add a 1meg trimpot in series with a 100K resistor so you can set it to your liking.
Hope that helpsStewart

I nestled a 1/8w 1meg resistor between pins 6 and 8 of the dual op-amp on the copper side of the board, and it worked like a charm.  My Blue Box can now come out and play with the other children.  Thanks, Stewart, wherever you are. 

[Earthscum]

*facepalm*

I figured that out on a octaver circuit before, kind of (actually, just made sense to build it in at the time), but I didn't know what I was doing and I think I pulled it out. The circuit kinda quit working after that, but I didn't know what I did. I've had problems ever since with the CMOS dividers, and I think that stupid resistor is the culprit in every one! The first one actually would not drive the second flip-flop for some reason after I pulled the resistor, which is the only part I didn't put back in.

This is good info, since Artifus brought up his SynFUZZsizer thread. Octave division is probably going to be coming up eventually, so I'm gonna definitely remember this (don't think it'll be hard now... I was cussing up a storm at every one I tried building. It's why I came up with my SCRynth, but I never have tried it in an octaver circuit).

Thanks, Mark, for sharing!

[Mark Hammer]

You're most welcome.  I'm glad I had them install a little applet on my work machine to save threads as PDF files, and I'm doubly glad I kept a bunch of these as files.  True, one can search for them here, but when it's gold like this, and it's saved with the filename "Bluebox fix" in a directory marked "Octave up-down", one is more likely to find it again when you need it.  Which is exactly what happened in this case.

[Earthscum]

lol... this is the circuit I came up with in retaliation of the (what I thought was) misbehaving OPA's. Obviously, I knew what needed done, I just didn't know how important that resistor was. Like I said, when I had built the first one, it seemed right, but looking at a schem, it looks goofy, like the 1k to positive at the OPA output of a DS-1, so I think I pulled it and never looked back... then just came up with this, which works pretty good... just quite a few more parts.



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