Feed back loop question

[SysCrusher]

 When I built Jack Orman's Son of Screamer, I couldn't figure out why the tone control wasn't working the way it should. Come to find out I had a bad solder joint on the feedback loop on the second stage. But the tone was really cool except the tone control. Is there any harm in not connecting the feedback loop?

BTW: Jack's Screamer kicks ass. I went out and bought the Wylde overdrive on a whim and it got returned after I compared it with the Son of Screamer.

[George Giblet]

You can connect things up anyway you want.

I'm not clear on what you left off.  I'm guessing the tone control wire that goes to the opamp's - input was left off.  Roughly that will make the tone pot act like the normal tone control in the full cut to 12 O'Clock range ie. the 12 O'Clock to Full will be lost.  So it still works - the full cut to 12 O' Clock region might not do that much.

The MXR Zakk Wylde Overdrive (ZW44) schematic is available together with layouts.  It's mostly an SD1 with different tone control caps:

http://www.diystompboxes.com/smfforum/index.php?topic=53522.msg406736
http://www.geocities.com/hmeffects/Wylde_Schematic_001.jpg

[SysCrusher]

The output to -input was left off. It sounded really cool; open in your face and not so compressed. Just the tone control wasn't what it should be but I think I can get around that.

It's been on my mind for quite some time so I'll have to build another with no feedback on the second half.

[chunks717]

I would say (without looking) that you probably removed the op-amp negative feedback which would put it in open-loop gain mode, which would be MUCH higher, (like 20,000 or so?! but less bias/gain/frequency stable etc).....which would also account for the change filter response.