Help Debug this huge sounding Fuzz circuit

[John Lyons]

Ok, last try here. Can anyone try this out and let the forum know your findings.

http://mrdwab.com/john/XORUS.html

This circuit produces a huge range of square wave textures.
I think it can be taken further But I'm in need of a sharper mind.
Check it out and see what you think you can come up with.
There are a lot of details on the site.

Thanks
John

[Sir H C]

Why not a switch to change some of those .002uF caps to something bigger? That could do some more fun things.

[digi2t]

Hi John,

I've been getting ready to build a DOF, when I came across this page;

http://mrdwab.com/john/XORUS.html.html

It states that the gating is fixed, but the sound clip link doesn't work. Seems to be an updated version of the page you linked in your original post.

I'm just wondering though, is the sound clip a straight DOF (as per Tim Escobedo's original schem), or the XORUS? It is the sound clip from http://www.mrdwab.com/john/soundclipspage.html, which is also the source for the older page, that is driving me to put together a DOF.
I would like to know if I should be building a XORUS instead. If so, I'll have to update the vero layout I just put together.

Thanks,
Dino

[R.G.]

At least on reason it gates because pin 1 is not held at any DC level at all. I think it would improve the gating issue to hold pin 1 at half the power supply with a pair of resistors or other bias supply. This holds it firmly inside the linear range of the gate, at neither a logic 1 or 0, so smaller pushes make it saturate higher or lower. It would not hurt to look at the biasing on the 2N5088 to make sure it's not gating as well.

A more organic solution would be to use some DC feedback from pin 3 to pin 1 to let it set its own middle-of-the-road bias voltage. Half the power supply is approximately correct, but won't cure gating completely for all instances of CD4070. You can keep the gain high by splitting the feedback resistor in two and using a cap to ground, same trick as used on the 5088.

You may need to lower the power supply voltage to avoid it pulling too much supply current, as with CD4049 based distortions. Frankly, that might be an advantage overall, so that's a good place to start looking. And I'd stick a resistor in series with that output volume control to see if I couldn't cut the max signal level back to a volt or two. There's plenty of gain in a guitar amp to make a volt or so of input signal be as "gainy" as you like, especially when the input is fed what's primarily a rectangle wave.

That ought to get it tamed a bit, and perhaps suggest some more directions to go.

[Solidhex]

That 10k on the emitter of the 2n5088 seems sort of big. Lowering it would give that stage more gain of course if that's would help get the effect you want.
Whoops! Wait. According to the diagram of the transistor the output is being taken from the collector but the "E, B, C" lettering contradicts that.

[John Lyons]

Woah, timewarp! 2006 in the house! 
It's been so long... thanks for the ideas RG. If I get time I'll
revisit this.

[clamup1]

this thing sounds awsome, ill have to wait on building this one, too many pies in the oven   

[~arph]

Ok, warpspeed two now..

Any chance of this schematic and accompanying soundclip showing up somehwere?

[pinkjimiphoton]

~arph, surf a little here, maybe you'll find something..sorry, don't have time for much spelunking, but i know at least some of the links work

peace

[~arph]

  I've tried that 

[pinkjimiphoton]

weird, the archive link is gone? or did i forget to post it? lol

[timd]

Yeah, what is it called?

[digi2t]

I've built the Digital Octave Fuzz, which is a scaled back version of the XORUS. As a matter of fact, it's the same as Escobedo's Stupid Cmos, but with a voltage divider supplying pin 8 on the IC.

It's got MASSIVE square wave fuzz, with the voltage divider really helping with the gating. My biggest beef is when I turn down the Fundamental (mosquito fuzz, but big volume loss), but I've always had the idea of adding a simple booster circuit (Beavis or Muzique), and changing the Fundamental pot to a dual gang. Turn down Fundamental /turn up booster type arrangement.

I just need to find the time to get at it though 

[timd]

Anyone have a schematic?

[John Lyons]

Here is the schematic.

[~arph]

Thanks John for digging this one up!

Very interesting

Regards,

Arnoud

[~arph]

I was expecting different gain stages.. along the line of this:



Not sure if that works by the way..
The idea is the same as your regular inverter gain stage. By tying one input of the XOR to V+ you make it an inverter.

[timd]

Thanks John!