Got any MXR Bluebox mods?

[Chris Goodson]

I just got through building one this morning, man this is one freaked out sounding effect.  It sound like the cheezy sound effects from an Atari with the blend knob cut all the way back.  But, I have been able to get some decent sounds out of it with a wah in front.

Anyhow, I was just wondering if there were any good mods for getting more sounds out of it?  Is it possible to change the pitch of the note it adds?

[Mark Hammer]

Congrats on a successful build.

You can't really attain anything other than octaves from it, but on the other hand, you DO have a choice of one or two octaves down.  The stock circuit delivers 2 octaves down.  Looking at Francisco Pena's "Caja Azul" layout (which I'm assuming you used), you will see that the octave side of the blend control has Q3 as a sort of buffer for the octave sound, which is, in turn, taken from pin 1 of the 4013.  If you lift the connection to pin 1 and reroute it to pin 13 of that chip, you will get ONE octave down instead of TWO.  You will note that the 4013 divides the input signal, and the second half of the 4013 simply divides that by 2 once more to get two octaves down.

Another useful mod is to take R17 and replace it with a pair of 27k resistors in series, sticking a 3n9 to 4n7 cap from each resistor to ground to form a low pass filter to tame the fuzziness and round off the tone of the octave.  That will make it a lot more liveable and also encourage you to turn the octave tone up.

There are other things you can do but these are two fairly useful mods to make it a more tonally flexible and more useable pedal.

[Chris Goodson]

Thanks Mark, I'll give it a try.  After playing with it some more I'm glad I built this one, it really get's a lot of crazy noises, it's definatly a good one to hook up if your bored with the same old sounds.  I might put together a Maestro Filter Sample/Hold soon and I can't wait to hear the two running together.