I have searched but have not found info on a possible C11 mod for the Caja Azul? Is it actually the c9 in the schematic? Are the parts in RED from the MXR reissue?
Thanks,
What mod are you trying to do? What is it supposed to change/fix?
With the Caja Azul being a clone of the MSR Blue Box. I was wondering if the c11 mod is still an option on the Caja Azul or if it has been taken into consideration in the schematic. The c11 mod on the Blue Box is designed to give you increased volume and enhanced sound.
Ahh... that mod. That mod simply removes the 0.01uF cap in parallel with the volume pot. The numbering isn't the same on the tonepad schematic, but if you take a look at the project file you can see the 0.01uF cap in parallel with the volume pot, labeled C9. A cool mod to do is using an on/off/on switch you can have the original value in one position, a different value in the opposite position (try a higher value 0.0047 or 0.0022) and in the middle you have the cap completely removed.
Nice! That is what I was looking for. Also, on the mod to only drop down one octave I have seen 2 different answers. On the 4013 to add a jumper between terminals 1 & 3, and 1 & 13. Which is correct?
I don't remember... i did do that mod to mine. If you do a search for "Blue Box Octave Mod" or something like that it should come up. Look for (or even do an advanced search) posts by Mark Hammer. He knows a lot about the blue box and I know he's posted that info before. And I know he knows what he's talking about.
I looked it up; it's 1 and 13.
That's what I thought. I would trust Mark Hammer over most other stuff I have seen.
Just searching his posts on the blue box in general will be very informative/enlightening.
Just curious on one more mod. Did you replace the 50k pot with the 100k linear pot for the Blend? Thoughts?
I diidn't try that- I've never heard of anyone doing that... is it supposed to do something? Looking at the schematic, I don't think it would make much difference
If you look upthis thread in this forum----- MXR Blue Box - 1/2 octave mod (dunlop reissue)
I posted the changes on mods you're asking about. I put partial schem examples up to show what I did.
I just drilled the box for the switches and pots. I added a SPST switch for the 1 octave mod along with a DPDT on-off-on switch for the C9/C11 mod. Like MikeH recommended the first position is stock .01uf cap, the second is no cap, and the third is a .0039uf cap.
(http://img249.imageshack.us/img249/8329/p4120028.jpg)
Thanks for the help. I am excited to get this wrapped up and see how it works.
Finished it. Definitely a weird effect. Is the "glitchy" sound normal? It seems to go back and forth from octave sporadically.
Yeah, the blue box doesn't track exceptionally well. You'll notice the closer you play to the 12th fret the better it tracks- also tracks best with the neck pickup. You could also try putting a compressor in front of it, that can help too.
Thanks for all the help.