Vocal Octaver Pedal

[Brynngar]

I couldn't find anything for this topic, so here we go:
I would like to build a stompbox which is a pure octaver effect with only a volume control. If it includes a bit fuzzyness - no problem.
I was thinking about going for something similar to this one: http://i257.photobucket.com/albums/hh218/reverse_engineer/schematics/15b69aa3.png

To be more precise, I am looking for: Voice goes in, gets pitched down an octave, modulated voice comes out. What I don't want is that the original voice is still audible.
Any suggestions for this project?

[Kipper4]

This looks like it could be designed with a guitar input rather than a vocal mic.

[amptramp]

The biggest issue with the octave down function is that the waveform you are feeding it may have enough harmonic content that there are multiple peaks that when subjected to an octave down treatment return the fundamental frequency.  The Boss OC-2 pedal has some circuitry that allows a proper octave down even with a waveform that would normally not work:



Following the signal chain in the lower part of the schematic, the signal goes through a low-pass filter to reduce the high frequency content then gets fed to a pair of active rectifiers set up as peak holds with some leakage to permit it to reset by itself.  The next set of comparators compare the signal peak to the current value of the signal through comparators that operate the set/reset inputs of a flip-flop to generate a gating signal to the next flip-flop which acts as a toggle divider.

The divider signal goes to an amplifer (IC5 pins 5,6,7) that is non-inverting when Q6 is off and inverting when Q6 is on.  This output goes through an all-pass stage to another invert-on-command amplifier (IC5 pins 1,2,3) to an output all-pass and the output is the sum of the input, middle all-pass and output all-pass signals.

This level of complication is used to allow reliable octave down effects even when the input waveform has more than one local minimum and maximum.

[Brynngar]

Thanks, I had already looked at this one, but since I'm more of a begnner in this field, I'm afraid that this schematic ist still a bit too much for me :/
That's why I was looking out for something more simplistic, like the schematic above.
Do you think it's possible to modify that one so you won't be able to hear the root note anymore at the output?

[midwayfair]

Thanks, I had already looked at this one, but since I'm more of a begnner in this field, I'm afraid that this schematic ist still a bit too much for me :/
That's why I was looking out for something more simplistic, like the schematic above.

Unfortunately, that's what's involved in getting a stable waveform. All that extra (scary) circuitry is there to prevent the wave from jumping around between the octave and the fundamental like a crazy oscillator, or from producing intermodulation and summing to "not an octave." You can do it simpler ... but it would involve programming a digital chip like the FV-1.

And yes, you can modify a typical octave pedal to remove the root note at the output. Take a look at the Madbean Lowrider. You could, in fact, just build a Lowrider and build a "wrapper" to be used with a microphone.

[Granny Gremlin]

This looks like it could be designed with a guitar input rather than a vocal mic.

Not a problem:

[Brynngar]

And yes, you can modify a typical octave pedal to remove the root note at the output. Take a look at the Madbean Lowrider. You could, in fact, just build a Lowrider and build a "wrapper" to be used with a microphone.

Ok, that one looks.. doable I guess. What do you mean with "wrapper"?
Also, does maybe anyone have this pedal and could maybe try it out for vocals? I wouldn't like to build it just to find out that it doesn't work that great with vocals :/

[thehallofshields]

To be more precise, I am looking for: Voice goes in, gets pitched down an octave, modulated voice comes out. What I don't want is that the original voice is still audible.
Any suggestions for this project?

The 'Downbox' that you're looking at is basically 2 diy projects combined, a 'Bazz Fuss' and a 'Shocktave'. If you want all effect, just turn that 'mix' control  all the way to right. and run the top-side to Go take a look a look at the demo's of some of those marketed under different names to see if that's really what you're looking for. My guess is that unless your're just looking for noise, you're going to hate it.

Try:
Bazz Fuss - JHS Minifoot
https://www.youtube.com/watch?v=b17icn1SVtM

Shocktave - Big John Granny Puker
https://www.youtube.com/watch?v=VRhg3yDAxf4

[Brynngar]

So, I had a look again at the Boss OC-2 and figured out that all I really need is that pedal, minus the Octave 2 option (one octave down will suffice!) Does anyone know a solution for that? Or is anyone "into the material" enough to cross out those unneeded parts in the schematic? Cause I saidly ain't 

EDIT:
On a second thought, and some google action later, I found this nice help which should make it quite doable!
http://www.sabrotone.com/?attachment_id=2173

So the question that remains is: Will this effect be suited for vocals? If not, could anyone suggest a nice workaround, like switching components etc? You will be rewarded with eternal internet fame and banana stickers!

[thehallofshields]

As an alternative to the Chopped OC-2, I would recommend MerlinB's UBoat. I haven't built it myself, but it's a simplified OC-2 with improvedTracking and Phase Inversion Switch for a unique sound. I think he even sells PCB's. The only caveat is that it's designed for -2 Octaves (f/4), but it wouldn't be difficult to design a switch to make a switch for -1 Octave (f/2).

http://www.diystompboxes.com/smfforum/index.php?topic=93387.0

[Brynngar]

That looks nice! Now all I need is a way to change the -2 Octave to a -1 Octave... 
And if anyone has seen a bill of materials for this project floating around somewhere, that would be handy as well!

[Granny Gremlin]

Merlin's writeup (aka Valvewizard): http://www.valvewizard.co.uk/uboat.html (links to BOM etc down below)

PCB and build doc by  TH Customs: http://diy.thcustom.com/u-boat-v1-5-suboctaver/

[Brynngar]

Thanks!
Still, that's 2 octaves and I'm afraid that's a bit too much for vocals (would only sound like mud).. So is there an easy way to modify the u boat
in order to achieve -1 octave instead of -2?

[nocentelli]

Thanks!
Still, that's 2 octaves and I'm afraid that's a bit too much for vocals (would only sound like mud).. So is there an easy way to modify the u boat
in order to achieve -1 octave instead of -2?

It's only one octave below the note you send into the input.

...you get ALL the control of the OC-2 from one knob (But no double-sub-octave, sorry).

Whether it will "track" vocals well is a different matter.

[Granny Gremlin]

Using a cheap hi-Z mic (vs a proper pro LoZ mic + an adapter as I posted above or other conversion method) will likely help with the uboat tracking vocals; they're more lofi and tend to have limited bandwidth/early rollof at the frequency extremes.  Look on ebay for old plastic bodied mics on ebay listed as for use with reel to reel tape machines.  The Shure Unidyne III (pretty much an SM657) also has a Hi/Lo Z switch but is very hidfi in comparison.  Another option would be a harp mic or any other mic that does that old radio/telephone thing.

Also note that there is a Track (sensitivity) knob on the THCustoms version of the uboat so the trackability is tweakable to a degree.

[FUZZZZzzzz]

we used the EHX octave multiplexer for that. instant barry white for what i recall