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Passive Octaver

PostPosted: Thu Nov 16, 2017 6:26 am
by Ben79
Hi all, I'm back from my travels and now partially installed in the mountains of Southern France.

A catologue of errors by my storage and removal companies has meant all my belongings were lost for 2 months but they've now been found and should be with me....before Xmas maybe :picard: So I'm starting to wonder what to do when I get my bits and my tools set up....

I'm gonna work on my Guitrumpaphone http://ilovefuzz.com/viewtopic.php?f=151&t=53136&p=1116504&hilit=guitrumpaphone#p1116504 I think and I'm also interested in a passive octaver, does anyone know how to make one? I know it's probably a transformer and some diodes like the end of an octavia....?

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Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 10:46 am
by BetterOffShred
Dan Armstrongs Green Ringer is a great passive Octaver IMO. EQD also makes a version with some minor value changes called "The Tentacle" which I've cloned as well. They are both Octave up, but I really enjoy them. Maybe worth looking at. Sorry to hear about your move fiasco, it's always something right?

Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 11:03 am
by crochambeau
Welcome back!

Are you playing around with the idea of a completely passive build, or just a passive stage in an active build?

The reason I ask is insertion loss. If 100% passive, the ass end of what you linked looks like a decent starting point; if you're providing drive and gain recovery you can throw more networks in there and build it out as a one input ring-mod.

Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 11:17 am
by BetterOffShred
I guess I don't understand the implications of the statement "Passive Octaver" I was thinking something with discrete components rather than a bunch of chips.. My bad ;)

Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 11:57 am
by crochambeau
BetterOffShred wrote:I guess I don't understand the implications of the statement "Passive Octaver" I was thinking something with discrete components rather than a bunch of chips.. My bad ;)


Passive = no power applied.

Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 12:20 pm
by BetterOffShred
I understand that definition of Passive.. but isn't there power applied to the effect even as shown above? It's generating the octave effect with just the transformer and diodes then?

Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 12:27 pm
by Ben79
Thanks guys.

Totally passive is what interests me at the moment - I think it's the notion of it being in a way part of the instrument that interests me, and the magic of seeming to produce something from nothing. Doesn't really make sense cos it's all gonna get distorted and amplified by an amplifier afterwards anyway.

I found this regarding the Octavia on here http://www.davidmorrin.com/home/trouble/troubleeffects/octave-up

Roger's original transformer and diode based rectification scheme is actually passive. He simply drove the transformer with enough signal to push through the passive stage.

Re: Passive Octaver

PostPosted: Thu Nov 16, 2017 12:38 pm
by Ben79
He writes this too:

Passive Octave
Two coils connected in parallel-opposing (parallel and out-of-phase) can produce an octave up effect. Normally this is about the worst possible wiring you can do for a 4 conductor humbucker. Don't expect this to sound good outside of the weird octave effect.

A neck position humbucker is the best candidate for this trick.

Some humbuckers may work better than others.

The theory:
The voltage combining at the "hot" side are two signals out-of-phase. If the signals were exactly the same and opposite, there would be 100% cancellation. A typical humbucker will just sound weak and strange with this wiring due to partial cancellation of the signal.

If enough of both signals remain audible, the ear should detect some degree of octave overtone. This effect will be greatest where string rotation is most symmetrical, which is about the 12th fret. The perception of an octave comes from the two signals "filling in the gaps" so the wave actually appears to be rotating twice as fast as the actual string.

If the loss of volume from the cancellation can be tolerated, it really does sound like you've switched on a clean Octavia effect by the flick of a switch on the guitar.

Re: Passive Octaver

PostPosted: Sat Nov 18, 2017 6:45 pm
by eatyourguitar
glad to see you back and doing well. let me know if you need any PCB's made. I would love to add something you designed to my store. we can trade.

Re: Passive Octaver

PostPosted: Mon Nov 20, 2017 6:56 pm
by Ben79
Nice to be back.

The idea of me having designed a circuit made me laugh since I have only the barest-boned idea of what goes on in them! But I do very much enjoy the sound that my mindless hacking of Escobedo's Bronx Cheer yielded in the the Guitrumpaphone. Maybe if it gets some momentum (and a better name?) in the DIY world then people will be interested in a PCB (even though it only has 9 components). To me it actually sounds a lot like the grungy tones of some vintage transistor synths; my old Octave Cat (that I had to sell to get here) for example.

Not having seen my things for a long time I had forgotten but I still have that street amp thing to finish.

And I saw an old intercom phone in a junk shop in town that I'm thinking could become some kind of talk box/ring mod/guitrumpaphone deal.