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I need help with my simple little effect idea.


merthurian
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Hi, i don't know much about electronics. But i don't see why this wouldn't be simple to do..

(I'm not very good at explaining)

I want to build a circuit that can chop the signal from my guitar at a variable rate.

(between about 1 and 100hz ish)

I want to have a bypass switch, and to be able to control the rate with a pot..

Can anyone give me any advice on how to build the circuit and where to get the parts from?

Thanks

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i think your looking for a Gate.

a gate cuts off desired frequencies, like an EQ or a hi/low shelf, but the gate eleminates a frequency instead of lowering it or raising it like an EQ.

so say i want to cut the lows on female vocals cause i was picking up a 60hz hum in the studio, then slap a gate and adjust it so anything less than 300hz is cut out.

that what your looking for?

t

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A gate is normally based on level/volume, rather than frequency. The reason gate pedals help to reduce hum in a setup is that if you set it so that it cuts off the signal when it's "only" the hum (the volume produced by playing even a light note is usually greater than the volume of the hum). When you're not playing notes, blissful silence. If you're using a distorted tone, the hum gets lost in the distortion. But if you listen carefully enough (or if you do it with a clean tone) you'll still hear the hum in there, while you're playing.

What you've described could theoretically be accomplished with some sort of gate, but I don't know of any gates that respond to frequency. That doesn't mean they don't exist! I just haven't encountered any in my amateur meanderings. What you're describing is usually accomplished with a high-pass EQ setting.

That said, it IS a gating effect he's looking for, but rather than an auto-gate set to close/open depending on volume, he wants one that will just open and close automatically, at variable rates which he wants to set with a knob.

Greg.

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I don't think i've explained it very well.. (my fault) it's a lot simpler than that.. i don't want to alter any frequencies..

Imagine having a toggle/kill switch that switches itself on and off at a variable rate.. between once a second and 100 times a second! I don't need it to respond to frequencies.. just kill the output from the guitar at a variable rate.

Has anyone here has used Cubase? i'm after the same effect as the Chopper plug-in.. But i'm only really interested in the square wave..

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i think that he means like an automatic kill switch that turns on and off at a set rate, so you can make it sound like an open note is actually being hit a lot of time, when it fact its still open

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OK, here's a simple down and dirty way to do it. Build a variable square wave oscillator (with the frequency range you want) with a 555 timer and use it to drive the LED of an optoisolator like a Vactrol, and connect the LDR between the hot and ground terminals on your guitar. When the timer output goes high, the LED will light, causing the LDR to decrease in resistance, essentially shorting the signal to ground. The slow response time of the LDR should keep switching noise to a minimum, and the timer circuit could be wired separately so it was completely isolated from the audio path. Enhancements would be buffering the input and output, could be as simple as a JFET source follower on both ends of the Vactrol, or using a VCA in place of the Vactrol. Like I said earlier, you can look at RG's Variable Stuttering Pedal over at Geofex for an example using Opamps and a JFET. It's pretty simple, the trick is going to make it reliable and quiet. Good luck.

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i recommend waiting for ansil to find this thread, and all of your questioned will be answered B)

but i do know that tremolo pedals aren't particularly expensive to build :D

hmm sorry didnt' realize i was being paged.. thougth i already did this thread i already have a nice choppy tremelo you can set it via two knobs and a 555timer.. use a cmos one if you want to make it low power.

i use it to drive a led ldr combo.. with a fixed resistor on the output.. if you set it just right it will chop it at that slow of a speed and also you can adjust it on how hard you want it to chop it,

personally i would mount the chop control on the back of a picguard with a small trim pot as once you get it in the right place no one ever moves it that i hav emade these for.

let me see if i can find the scheme

btw you can build this on the back of a quarter if you are good. on a nickle if you are real good. and well on a dime if you are me.. lol

http://www.geocities.com/austenfantanio/we...gout/mytrem.htm

feel free to look around there that is wehre most of the stuff is that i am weeding out. http://www.geocities.com/austenfantanio/weedingout/

i have limited bandwidth however so goodluck

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Sorry Couple more questions...

What is the 'Gain Stage'? .. and what voltage battery do i kneed?

a gain stage is the part of the circuit with the tube/opamp/transistor that actually amplifies the sound. Usually in a distortion pedal you'll see a few of them linked together to add more gain to the sound. In an amplifier, you see quite a few of them.

I wish I could explain it better than that, but my verbal skillz aren't that mad...

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9v batterie and a gain stage is like a single opamp gain of two. you can do without it.. but it helps out a little

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Actually, you could probably get away with a buffer like a unity gain opamp or a JFET source follower - Although both are technically "gain stages", they wouldn't actually boost your signal, just minimize interaction with the LDR to avoid losing highs from loading. A J201 source follower would take 5 components (two caps, two resistors and the FET), and give you more than 5 volts p-p for headroom with very little current draw. Put one before and one after the LDR, you've got a robust, simple circuit that should be quiet and well-behaved.

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