Anyone know a simple octave-down build? ???
The Blue Box and the PAIA Rocktave divider are the standards. The Roctave is available as a kit and is frankly the best non-DSP octave down I've seen. Highly recommended.
But no, there are no two-transistor octave downs. They'll all have a CMOS CD4013 flipflop chip, input conditioning circuits, and then output filtering.
Check out the non-chip Shocktave http://www.diystompboxes.com/smfforum/index.php?topic=69097
The slacktave is pretty simple http://www.diystompboxes.com/smfforum/index.php?topic=55644.0 (http://www.diystompboxes.com/smfforum/index.php?topic=55644.0)
A more DIY friendly version of the Boss octave down, 3 chips, not too bad. The fundamental extractor is a clever and economical design, better tracking than other more expensive analog octavers I've tried (haven't tried the Rocktave).
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=9447&g2_serialNumber=2)
For simple I would say the Shocktave is as easy as it gets for a simple circiut for octave down. I etched a PCB that Marcos sent me and built it for my brother. I put a millenium 2 bypass circuit in for the LED from geofex. The Shocktave is another Joe Davisson clever design.
I also perfboarded the MXR Blue Box which isn't too bad although you need a 4013 IC and a 4558 dual op amp. I modded the Blue Box with a SPDT switch for the 1 and 2 octave down and jumped around C9 with a switch for a higher frequency volume. I am going to check out the Rocktave as soon as I can get around to it. The Boss circuit looks interesting also. I'll look for the 4024 IC for the Slacktave too.
BLUE BOX
http://i218.photobucket.com/albums/cc93/ftrock/bbmods.jpg
http://i218.photobucket.com/albums/cc93/ftrock/bb1n.jpg
http://i218.photobucket.com/albums/cc93/ftrock/bb4n.jpg
Shocktave
http://i218.photobucket.com/albums/cc93/ftrock/pl3.jpg
http://i218.photobucket.com/albums/cc93/ftrock/pl2.jpg
Which one of these is the simplest in function? I dont need any distortion . I am only needing an Octave down all by itself. A clean/octave mix knob would be nice. The POG looks nice but it so expensive>>>>>
Clean octave down is beyond the scope of DIY octave down circuits.
Well, if you're just looking for a simple octave down, there are some cheap multipurpose digital effects that work nicely. I've got one of the cheapo DigiTech pedals. I think mine's the RP50, but you can buy others with expressions built into them and "eq" knobs. It does nice phasing and envelopes, and the octave ups are pretty spot on. There is an octave down and a double octave down, both are a little funky sounding. The single octave down sounds bright and digital like, but the two octave down sounds much more smooth and clean.
Not really something to build, but for $50 you sure can do a lot of stuff. I'd try it out at the local music shop first before I bought it though because the build quality isn't very high.
Or the typical DIY octave down answer: build/buy a bass.