Craig Anderton Rocktave Divider

[MAO]

Another classic gem from the guy who started the DIY craze for me.

This pedal sounds wild and tracks amazingly well (single notes). Tracks much better than the octave doublers I have built.

I've updated the layout to use a TL074 and added all the mod options including the extra divisions.  

The schematic, circuit analysis and mod details can be found in "DIY Projects for Guitarists" and/or from the original 1983 GP article courtesy of Mark Hammer http://hammer.ampage.org/files/rocktave.pdf

There are many options to wiring this up, here is what I settled on:

The layout was originally designed to be rotated clockwise to fit in a 1590BB.

At the time I thought I would end up using a toggle switch to choose between 2 of the extra divisions from the CD4017 mod. But after hearing each available division, I wanted them all . True, divisions 7-9 are not as "musical" as the others, but still cool. A SPDT toggle and mini 2P4T rotary will do the trick. Unfortunately the wiring is a bit cluttered due to the parts placement, but there are 9V and ground connections on both sides of the board so it can be rotated CCW if preferred.

Of course you don't need to use all 8 divisions from the CD4017, or the jazz, buzz or (buffered) byp options. But here is how I implemented some of the possibilities:

I added a SPDT switch to allow the Octave 1 control to select either of the CD4013's "divide by 2" or "divide by 4" outputs.

For the Octave 2 control, I used a mini 2P4T rotary switch and have pins 1 though 8 going to each of the 8 division outputs of the CD4017, with pins A & B going to the outer lugs of a SPDT toggle switch and the middle lug of the SPDT going to pin 15 of the CD4017 (though the 1k resistor). This allows the Octave 2 pot to control any of the 8 available divisions from the CD4017 depending on position of the rotary switch and which way the SPDT toggle switch is thrown.

I used SPDT toggles for the "jazz" and "buzz" options. The buzz mod adds even more volume (the pedal is already above unity with the stock R17 value). I may end up using a DPDT so I can alter the value of R17 at the same time keeping the volume consistent when engaging this mod.

The BYP connections allows for the original buffered bypass if desired.  
 
Verified


Reversed image for the cuts



sample layout


BOM

100R
1k-2
4k7
10k-10
22k-2
30k-3
47k-2
100k-2
270k
470k
680k
1M-2
2M2

5k pots-4

330p
100n-4
220n-2
1uf NP (Jazz mod)

1uf-2 (or use a 1u NP for output cap)
2u2-3
4u7-1
10u-2
100u-2

1N914
1N4001
2N3906-2

TL074
NE570 orNE571
CD4013
CD4017

And a couple other resistor and cap values to taste for the CLR and tweaking the socketed components (see original text for details)

mini 2P4T rotary switch (I have a couple I can spare if you don't want to buy a lot of 20)

http://www.ebay.com/itm/20pc-Rotary-Band-Switches-DC-60V-0-3A-100-500-ohm-2P4T-10-Pins-2-Pole-4-Position-/300881322642?hash=item460deca292:g:yUYAAOSwRLZT6z-D

[Kinski]

Wow. So this thing can do other intervals besides octaves?

[MAO]

Yes, the divisions mod adds options for divide by 3,5,6,7,8 or 9. You can also combine any one of those with either the divide by 2 (1 octave below) or divide by 4 (2 octaves below).  

Check out the last page of this pdf for the corresponding notes provided by each division.

http://hammer.ampage.org/files/rocktave.pdf

Play an open high E string and the listed note at the same time to have an idea of what it will do. But I can tell you, after doing that myself I thought I would only use the divide by 3 for a cool harmony sound, but the other divisions sound much better than I had expected. Crazy synth like sounds.

It's funny, on a couple of the settings you'll think you are on the wrong fret or maybe playing backwards. It might just be a novelty, but kinda cool.  It made my think of how the guy from Collective Soul would throw in some wild sounds here and there.    

The fuzz is pretty thick too.

I hope to record a sound sample next week.  

[MAO]

Here's a sound sample of the divisions.

https://soundcloud.com/maopedals/rocktave-divider

[MAO]

So I added a level control, highly recommended for dialing in unity gain.

I removed the socketed 100k output resistor (lower right corner of board) and took the "Out" wire to lug 3 of a 100k audio pot, lug 2 is the new output and lug 1 to ground.  

I also re-ordered the 2P4T connections so the divisions are paired more logically when flipping the Octave 2 toggle from A to B.  2 is opposite 4, 3 is opposite 5, 6 is opposite 8, and 7 is opposite 9.  

Here's the 2P4T switch vero I used, which fits under the main PCB with a thin piece of cardboard between the two. Just trim the legs of the rotary close.  



Updated layout:



Updated 1590BB Faceplate:


   

     

[SonusFluxa]

Finished putting this together last night using the updated layout (but not the baby board for the rotary). It didn't fire up right away, but I just chalked that up to the fact that it was 5 am and put it aside until I woke up. Sure enough, it wasn't behaving. I was getting fuzz at most but no octaves.

I replaced the 2n3906s with 2n3904s on a whim, swapped their orientation, and the 2/4 octave worked.

I poked around until I found that I got the crazy rotary octaves when I added a jumper over the cut between pin 14 of the 4017 and pin 3 of the NE570.

Now it sounds great! Glad I got it working. The jazz switch is an awesome addition, definitely helps when I want a subtle craziness and not a full on. BTW, using an electrolytic in the sockets for the jazz switch, I'm waiting for np's to arrive.

Thanks for another awesome layout MAO! I still have to upload a demo of the quadrafuzz!

[MAO]

Wow, sorry you had trouble.

Not sure what to make of it, the design definitely calls for 2n3906s and the orientation on the layout is correct. And I have no idea how jumpering over the cut mentioned brought it to life.

But glad you got it working.

Looking forward to your Quadrafuzz demo. I have built another one (4136 version), should have it boxed up in a week or so.

[SonusFluxa]

It's almost 100% something that I did wrong while building, I'm just glad I got it working and figured I'd share my weird workaround. I'm a solid supporter of your layouts! Keep em coming.

[pedro.affonso]

Thank you so much for that hint! I switched the 3906's for NPNs and inverted them and it worked just fine!!

I started building this pedal 2 years ago and spent many days of work trying to figure out why the octaves didn't work (the fuzz sounded ok). It was hard because I don't have an oscilloscope and don't undertand completely how this circuit works, but it seemed to be some biasing issue with Q1 and Q2 - their output wasn't high enough to trigger the flip-flop's clock.