Are feedback circuits difficult or overly involving?

[lowvolt]

To be clear, what I am asking about is something that can be engaged with a footswitch that will produce "feedback sounds".

Is that something that can be simply added to (let's say) an OD circuit?

Thank you.

[nocentelli]

You *can* simply connnect a wire from the output of a dirt pedal back to the input to create instant feedback. You can have a switch to cut this feedback in and out, and maybe a pot to control the amount of signal that is fed back. You can run it back via a resistor and cap to ground to alter the tone of the feedback signal.

The problem with these methods is the unpredictability and instability of the feedback: it's very often just an annoying whistling tone behind everything you play, and often highly interactive with your guitar's volume + tone pots. You might like this. A better way of accomplishing this is a dedicated looper pedal with a feedback switch and pot: Beavis audio has a design, or search for "krok feedback pedal". Both are simple 3PDT loopers with a switchable feedback path with level pot. Put a selection of pedals in the loop, then engage them and their output is fed back into the input alongside your guitar signal. Electonically generated feedback is much more interesting if it is fed back through delay, chorus, phaser, reverb etc which colours the sound and gives a bit more interesting texture than basic oscillation.

I would suggest breadboarding a simple OD/distortion/fuzz circuit, get it working, and then experiment with a feedback path, or just have a go at building the Beavis/Krok pedal: It's a nice simple DIY starter project with a few simple parts.

[lowvolt]

You *can* simply connnect a wire from the output of a dirt pedal back to the input to create instant feedback. You can have a switch to cut this feedback in and out, and maybe a pot to control the amount of signal that is fed back. You can run it back via a resistor and cap to ground to alter the tone of the feedback signal.

The problem with these methods is the unpredictability and instability of the feedback: it's very often just an annoying whistling tone behind everything you play, and often highly interactive with your guitar's volume + tone pots. You might like this. A better way of accomplishing this is a dedicated looper pedal with a feedback switch and pot: Beavis audio has a design, or search for "krok feedback pedal". Both are simple 3PDT loopers with a switchable feedback path with level pot. Put a selection of pedals in the loop, then engage them and their output is fed back into the input alongside your guitar signal. Electonically generated feedback is much more interesting if it is fed back through delay, chorus, phaser, reverb etc which colours the sound and gives a bit more interesting texture than basic oscillation.

I would suggest breadboarding a simple OD/distortion/fuzz circuit, get it working, and then experiment with a feedback path, or just have a go at building the Beavis/Krok pedal: It's a nice simple DIY starter project with a few simple parts.

VERY informative .... thank you very much for your willingness to help.

[Thecomedian]

Do you want to make a pedal that mimics what happens in this video?

http://youtu.be/luURyH9fzhk?t=1m50s

http://www.ultimate-guitar.com/forum/archive/index.php?t-235067.html
http://en.wikipedia.org/wiki/Audio_feedback#Deliberate_uses
http://electronics.howstuffworks.com/gadgets/audio-music/question263.htm

[lowvolt]

Do you want to make a pedal that mimics what happens in this video?

http://youtu.be/luURyH9fzhk?t=1m50s

http://www.ultimate-guitar.com/forum/archive/index.php?t-235067.html
http://en.wikipedia.org/wiki/Audio_feedback#Deliberate_uses
http://electronics.howstuffworks.com/gadgets/audio-music/question263.htm

Yea, I suppose.  So I guess you're suggesting I check the other links then.

[nocentelli]

Those links are all concerned with acoustically-generated feedback, which is simply a matter of turning up the gain and pointing the guitar towards the speaker. As I read it, OP was asking for a pedal to replicate this.

[Thecomedian]

I thought it might be what they were looking for. Apart from nocentellis advice, I wouldn't presume how to do this successfully, but the links might have some value in understanding the intended behavior that should go on "in circuit".

It could probably work well on a Wah-like pedal.

[lowvolt]

Y'know, I've been thinking about how to set up a proximity trigger of sorts.  Something like a theremin that I could actually have some sort of actual control over pitch and volume.  There are some great CV type controllers that provide control over voltage by simply moving a hand (or guitar headstock) near the controller and somehow producing pitched feedback.  Perhaps I could fret a note, simply sortof "tapping" it, then adding a boatload of gain via a "feedback circuit" brought in with a momentary footswitch and controlling the gain with the proximity device.

So, step on the momentary footswitch to increase the gain by a truckload (via the "feedback circuit"), fret/tap a note to control the pitch, and move the headstock towards the proximity device to have some control over the amount of gain.  Add some "theatrics" to make it believable and call it done.

I've seen Joe Bonamassa do some incredibly bitchen stuff using a Moog Theremin simultaneously with a feeding back guitar.  He creates these soaring/seering sounds when the guitar's pitch and the theremin's pitch go in and out of perfect intervals relative to one another.  Sometimes the two are producing perfect fifths (or pick any perfect interval) and other times the two are producing dischordant intervals.  It's quite inspiring.  It was one of his performances that got me to thinking about something along those lines.

Back to the feedback circuit with gain controlled by a proximity controller.  Is this possible without building an entire modular synth?  I am pretty well versed on modular synths, and I know I could rather easily create a simple synth setup that would use the proximity controller to control a VCO's pitch and volume.  But I'd rather try to create the same effect using a guitar's sound rather than a synthesizer's VCOs.  Basically using some sortof feedback circuit to produce gobs of gain and sustain (Along with a well designed OD/Dirt circuit) and then use a proximity controller to create the volume control.  So essentially creating feedback ... controllable feedback .. without the need for overwelming amounts of amplifier volume to do it.

Any ideas?

[Pojo]

There's always the Boss feedback pedals. It's way over my head how they work though.

http://www.diystompboxes.com/smfforum/index.php?topic=96906.0

[deadastronaut]

fender runaway...

http://www.youtube.com/watch?v=LaMEdWHiLno


be nice to know how this works...hmmm..