MXR Blue Box ? for Mr. Hammer

[jmusser]

Mark, you mentioned on a post for the Mods to the Blue Box a while back, that by switching pins on the flip flop, it could be changed from either a 2 octave down original, or one octave down. Can these two tones be used at the same time from a split output for extra thick goodness? Also, could it be modded to blend these tones  (or even just the original second Octave down) like Tim does with his Octup Blender?

[Mark Hammer]

Yes.  Take a look at the Rocktave schematic posted over at GGG.  Anderton provides a means to mix down the divide-by-2 and divide-by-4 outputs.

Note that the BB assumes ONLY the divide-by-4 and only provides a means to mix that in.  I'm not sure whether your own needs/preferences would dictate a separate blend-between-octaves-below and blend-between-fuzz-and-octaves or simple level of F/2 and F/4.

[jmusser]

Thanks Mark, I'll check it out. For me, it would be fine to be able to have them either both on at the same time, and an either/or selection.

[Mark Hammer]

If either/or suits you, then all it takes is a switch that taps pin 13 of the flip flop chip for divide-by-2 instead of pin 1 for divide-by-4.  The flip-flop end of the 1M resistor goes to the switch common (a SPDT will do you) and the side lugs go to either pin 1 or pin 3 (which remains connected to pin 13).  That's it.

Note that any filtering applied to roll off the buzz on the lower notes should probably be altered or alterable to suit the harmonics of one versus two octaves down.  The .01uf cap off the volume pot is useful for rolling off some of the fizz and buzz, but you can probably get a more usable octave-down sound by tacking a .01uf cap to ground off the octave side of the blend pot.  That, and the 56k resistor that leads up to it will form a simple lowpass filter to round some of the edges off the square wave from the flip-flop.