mxr blue box- octave switch mod?

[choklitlove]

i'm trying to make the blue box (http://www.tonepad.com/project.asp?id=33).  i was reading the 'build reports' and one of them says: "I made a modification, put a switch to make a jumper between the pins 1 and 3 of the CD4013, and you´ll get a switch to 1 and 2 octaves down."  i'd really like this mod, if i could understand how he did it a little better.  maybe whoever said it posts here and could help me.

anything?

[octafish]

Use the search function using "blue box mark hammer" You'll find a bunch of info on the blue box and possible mods.

[choklitlove]

i searched and found some ideas.  but nothing very specific on how to do them.  i know that there are two lugs of the ic that control which octave below it makes.  then there is one out for the two.  that must mean i could use an spst with the out in the middle and those two on the outer lugs, correct?

[choklitlove]

know what i mean?

[Mark Hammer]

Think of the 4013 as being used here like phase shift stages (oh god, I know I'm gonna regret that one.....).  With a complex phase shifter, you migh tap the phase shifted signal after 2 stages, 4 stages, 6 stages, etc., expecting more phase shift the further along you tap.  Well, in this case, the 4013 just keeps in dividing by 2.  If you tap the 4013 at pin 13, the signal has only been divided by 2 once at that point.  If you tap at pin  1, it has been divided by 2 again and is an octave further down because of that.

So, disconnect the end of R11 that goes to the chip, and install a SPDT two position toggle.  The "free" end of R11 goes to the centre lug on the switch. One of the outside lugs goes to pin 1, and the other outside lug goes to pin 13.  You do not need (and shouldn't) cut the connection between pins 1 and 13.

That's it.

[choklitlove]

thanks.  i'll be ordering parts soon, so i'll probably be back with some questions once the build starts.  thanks again!