Logan Sound - Wah Anti-Wah

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puppiesonacid
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Post by puppiesonacid »

flood wrote:hey there puppiesonacid,

i have built this circuit, albeit a very long time ago. it didn't do much for my guitar - i think i should have tried putting a buffer before it, but sounded kinda cool with a drum machine.

when this thread was opened, i revisited it and simulated it in circuit maker. changing the cap cvalues, or misbalancing them makes a huge difference to Q. i got some very interesting waveforms.

i will probably BB this circuit soon, with an added distortion stage to follow it. i actually came up with a layout for it in eagle - wah, distortion, volume and two 6 position switches but lost it due to data corruption. probably better that way, since i tend to make layouts for things whose function i'm unsure of.

will pop out the ol' breadboard this week and see what i can find...

Flood, do you mean you built the anderton version? when you say you'll get the breadboard out, do you mean you'll try the Logon Sound? :hmmm:
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flood
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Post by flood »

hi,

this was one of my first ventures into DIY, around 2002... i got the parts together and built a small crappy prototype using the anderton circuit, that surprisingly worked off the bat. i simulated the frequency responses only recently though. sadly, i don't have the simulations anymore, because the software i used does not work on mac - i changed systems...

as far as i can tell, the anderton and logan versions are functionally identical. i would prefer to use a dual opamp, for the simple fact that i do not have any single opamps and i save a bit of space too. :)

so the question as to which version to build doesn't really arise...

sent you a PM; will post more if i get the time this week to give it a run. cheers!
In the interest of full disclosure, I am Animal Factory Amplification.
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RnFR
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Post by RnFR »

bahump...

any luck with this circuit?
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earthtonesaudio
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Post by earthtonesaudio »

I noticed a couple questions regarding whether the filters sweep or are fixed and simply "panned between." With this topology, each filter is swept, in opposition to the other.

You don't often find schematics for sweepable bandpass filters, but check out the "single op-amp bandpass filter" here: http://ourworld.compuserve.com/homepage ... /opamp.htm and you'll see the one Craig Anderton used.

The resistance-to-ground between the feedback capacitors is used to sweep the sound. Less resistance to ground means less negative feedback at the frequency determined by the caps, so the tone gets brighter... and at the same time, less resistance to ground means a higher roll-off point for the highpass filter created by the cap on the (-) terminal, which reduces bass and causes a perceived increase in brightness. I've seen this filter type called by the name "multiple feedback" and perhaps this is why.
rocklander wrote:hairsplitting and semantics aren't exactly the same thing though.. we may need two contests for that.
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Post by RnFR »

thanks for the link- i think it might help me get away from my opamp phobia that i currently have. i think it stemmed from a dislike of diode clipping distortions and OD's, but there are so many other cool things to do with op amps, and i'm starting to feel like i am limiting myself. i'll give it a good look.
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Post by puppiesonacid »

when I built this on vero, I couldn't get the guitar signal to pass but I could hear the pot pan between the two circuits, any ideas as to what I did wrong?
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Post by Fuzzer »

I had an idea similar to this, have everything to build it through this vacation period, two bespeco weepers in series, you adjust each one with apot, or adjust both of them at the same time with a dual ganged pot, or do the wah anti wah thing with one of the halves wired backwards and the other one wired normally.
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Post by sinner »

Description of this is so similar to WahFull, before M.Fuller edited his page with his concept for fixed wah. There is a shot of trace side on effectsdatabase.com not much helpfull, but hey! at least it's something ;)

Cheers
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