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Bob's octave fun

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10/17/2000 1:11 AM

Bob's octave fun

Since this circuit is starting to gain cult status on this board I had to join in on the fun. The fact that it is cheap, easy and all stock Radio Shack helped. I was wondering if anybody was yet to perform any cool modifications yet. Any recommendations , esp from the sonic youth realm, would be greatly appreciated. This thing already produces some great distortion with the gain cranked.

Cheers
JMF

10/17/2000 5:29 PM

I've done 2 mods to my octaver. The first mod is to put a 0.1 uf poly cap between the V+ and the ground. It should be as close as possible to the actual chip, ideally straddling it from the V+ on the one side to the V- / ground on the other. This prevents oscillation and lowers the amount of noise. The second mod is to add an extra gain control, the traditional LM386 style. Connect the positive side of a 10 uf 16 V electrolytic to pin 8 and connect a 100K pot between the negative side of the cap and pin 1. With this mod, you can really give is a hell of an output boost, plus more easily change just how fuzzy the signal is. Hope that's of some help.
-Dan

10/17/2000 5:51 PM
aron	Thanks for the mods Dan!

10/17/2000 8:19 PM

quote:
"The second mod is to add an extra gain control, the traditional LM386 style. Connect the positive side of a 10 uf 16 V electrolytic to pin 8 and connect a 100K pot between the negative side of the cap and pin 1."

That's clearer than the app-note I have.
Thanks, Dan,

-Eric

10/18/2000 5:31 AM

Hey, Alien Dan, I did your mod and I love it!

The folks at my local Music Go Round loved it, too.

Prior to the mod I took the unit along with the newly built FF clone to a jam night. After the band quit playing , I plugged into a Super with those 2 boxes to demo them to a buddy of mine. Within a minute, there were about 8 people all standing right around there to check it. Lotta smiles. We passed the guitar around to different players- everyone becomes a little Hendrix-y when presented with those sonic colors.
The units got a buncha thumbs up.

10/18/2000 11:07 PM
Dan	Glad to know you guys like it . You can get also get some pretty interesting (almost synth-like) sounds by driving it with an autowah. -Dan

10/18/2000 11:42 AM

This is starting to sound like fun. I've got an LM386 laying around in my parts bin - I knew I'd have a use for it some day. Also got an electrical junction box waiting to be stuffed with these wonderful Radio Shaft parts.

Question for anyone playing with the LM386 gain control: Did you still have to drive it with a fuzz box when you cranked up the LM386 gain?

I love simple stuff like this that sounds good. Thanks for the schematic and sound sample, Aron!

Doug

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