Tone Generator: Just a fuzz in a feedback loop right?

[Hot_Rats]

yeah? then what would be the best choice for the fuzz in the loop? cheapest i mean. i dont think i need control over fuzz or volume just pitch.

[Greek Acorbat]

I've never tried a fuzz in a feedback loop (or anything else for that matter   ) so I don't know how it changes pitch and so I won't know what's required for that.

But for a quick fuzz the best idea would be to throw one together yourself. You could try something like Colin's PU and strip it right down. Like just use a 386 with pins 1 and 8 shorted. If the clipping isn't hard enough you might try a couple of silicon diodes to ground on the end. You could certainly do something like that with a part count of less than 10.

[Greek Acorbat]

You may need to buffer it however. I tried putting a feedback loop onto a breadboarded 386 circuit I was trying out a few weeks ago. All I got was a nasty clicking sound. So maybe a buffer would help with that (? Colin?).

[expanoncolin]

No no no, IMHO by far the easiest tone generator is a 555 one-it does output an uneven square wave and nothing like a good sine wave, but when the waveform is unimportant and you just need a tone 555's do the job quite well, and you can get them at your local radioshack, or from me, I have about 30 extras lying around.

Here's a good schematic:



The frequency range is a bit high, as you can see, but it can belowered by changing the value of C1.  I'd personally go for a .22uf capacitor.

If you wanted a volume control, I'd just put a 100k or so pot to ground right before the output's hot wire (you'd be replacing the speaker with a 1/4" jack on the schematic).

If you really want to do a fuzz in a feedback loop for a tone generator, then by far the easiest would be the easy face:



Youd then basically just want to put a pot wired as a variable resistor from the input's hot connection to the output's hot connection.  Normally the pitch is changed via the gain or volume knob.  You'd want to put the output coming from after the variable resistor somewhere, and then have a 100k or so pot to ground to control the level.

The problem with this is that it's pretty unpredictable, not very amplitude stable, and not an easy to slap together design because of the trannies.

The 386 is certainly good for making a fuzz like that.  Try wiring it like this:



You can ignore the 250uf cap, and you're going to want to put the 10uf cap in there.  Replace the speaker with a jack.

You'd then want to put this at the output, right before the jack:



Good luck!

-Colin

[Hot_Rats]

Thanks for all the help. im goin with the 555s.

ive been playing my muppet babies keyboard (like a casio VL-1 with out record mode, same cheesey song an everything) with my toes as i play guitar and its getting really difficult. i think if i put 5 or 6 tone generators in one box with easier to push foot switches i can get the job done better/easier. like a basspedal system.

[Greek Acorbat]

Ah, if that's what you're planning to do with it then I imagine that a dedicated tone generator would be a lot more predictable than a fuzz in a feedback loop.

That 555 circuit looks pretty funky, I might give that a go sometime.

Colin, out of interest, do you happen to know why I was getting clicking with a feedback loop on the 386? I haven't heard of that happening to anyone before.

[expanoncolin]

Ah, if that's what you're planning to do with it then I imagine that a dedicated tone generator would be a lot more predictable than a fuzz in a feedback loop.

That 555 circuit looks pretty funky, I might give that a go sometime.

Colin, out of interest, do you happen to know why I was getting clicking with a feedback loop on the 386? I haven't heard of that happening to anyone before.

Clicking?  How do you mean?  Did it just click once, or constantly, or what?

-Colin

[Greek Acorbat]

Continually. Altering guitar volume changed the frequency (as in clicks per time rather than pitch) of the clicks. The loop was simply a 470K pot taken from before the input cap to after the output cap.

It kinda befuddled me.

[expanoncolin]

Continually. Altering guitar volume changed the frequency (as in clicks per time rather than pitch) of the clicks. The loop was simply a 470K pot taken from before the input cap to after the output cap.

It kinda befuddled me.

Interesting, perhaps you were creating a square wave oscillator as shown on the schematic.

-Colin

[Greek Acorbat]

Hmm, it's this kinda time I wish I had an o/scope. I might mess around with circuit a little more if I get a chance to.

[expanoncolin]

Hmm, it's this kinda time I wish I had an o/scope. I might mess around with circuit a little more if I get a chance to.

http://ebay.com

The answer! :flehan:

-Colin