PFUKR250 - Dearmond Square Wave

[matmosphere]

Made this one for Pedals For Ukraine. Didn't think I would get it done on time.

It's a Dearmond Square Wave (which is basically a 250 anyway) but I used a LM308 (with a 100pf cap soldered between legs 1 and and 1n695 diodes. I also made several changes to the capacitor values to try and make it more bass friendly.  So I guess that makes it a Sub-harmonic Rat-ulator 250 right?

It sounds really gnarly and cool on guitar, but the volume has to be cranked to almost max for it to reach unity gain and I didn't have a 500kC for the gain pot so I used a 500kB so most of the control there is in the second half of the sweep. I think it still retains some of the 250's vibe though. If I had to do it again I'd make the volume be an internal trimmer and make sure I had a reverse log taper pot for the gain.

Anybody have a suggestion to increase the output volume? Might wait to post it to see if I can get that sorted. I think the diodes are clipping pretty hard and it's really throttling the volume. I tried several different sets of diodes but nothing sounded anywhere near as good. Also tried stuff with a tl071, sounded different and good as well, but I like the lm308 a little better.

The artwork on this one actually comes from a manhole cover in Kyiv that I have been wanting to put on a pedal forever. It's clearly a high voltage take on the Ukrainian Trident logo.

[harryklippton]

That looks really cool. I always try to take notes on stuff that I find visually inspiring

[mauman]

Anybody have a suggestion to increase the output volume? Might wait to post it to see if I can get that sorted. I think the diodes are clipping pretty hard and it's really throttling the volume. I tried several different sets of diodes but nothing sounded anywhere near as good.

(Schematic here for the mostly similar MXR Distortion+: https://www.electrosmash.com/mxr-distortion-plus-analysis )

You're right, the limiting factor on output level is the forward voltage drop of your Ge clipping diodes since there's no gain stage after the clipping stage.  You could try diodes with a higher Vf than the 1N695.  If you don't like Si diodes or LEDs, here are some other options from Jack Orman with nice response curves:
- MOSFET or Zener in various configurations, http://www.muzique.com/lab/zenmos.htm
- Add a clipping saturation control to your current diodes to raise the Vf, http://www.muzique.com/lab/sat.htm and http://www.muzique.com/lab/sat2.htm

[benny_profane]

Looks great! Dig the inspiration behind it too. You could try doubling the diodes so there is a parallel set of two series diodes each way. That'd get you up to Si Vf territory while retaining the Ge texture.

[EBK]

You could try doubling the diodes so there is a parallel set of two series diodes each way. That'd get you up to Si Vf territory while retaining the Ge texture.

Yeah, that's what I did.  Look here for lots of great ideas:
https://www.premierguitar.com/amp/mxr-distortion-plus-mods-2651041927

[Thewintersoldier]

Looks great Matt!

[storyboardist]

That looks fantastic Matt!

[Bio77]

Awesome build!  I also have some pictures of manhole covers from traveling   You run across some cool ones in other countries.  The ones in my neighborhood all just say sewer..pretty boring 

[harryklippton]

Awesome build!  I also have some pictures of manhole covers from traveling   You run across some cool ones in other countries.  The ones in my neighborhood all just say sewer..pretty boring 

Wait you have manhole covers in your neighborhood? 🤣

[benny_profane]

Awesome build!  I also have some pictures of manhole covers from traveling   You run across some cool ones in other countries.  The ones in my neighborhood all just say sewer..pretty boring 

Wait you have manhole covers in your neighborhood? 🤣

You don't cover man holes in your neighborhood?

[matmosphere]

Awesome build!  I also have some pictures of manhole covers from traveling   You run across some cool ones in other countries.  The ones in my neighborhood all just say sewer..pretty boring 

Wait you have manhole covers in your neighborhood? 🤣

You don't cover man holes in your neighborhood?

There was one a manhole with no cover on the street right by my old place for a long time. Somebody put a chair sticking out of it so cars didn't drive into it before it was fixed. The chair disappeared after a while but the hole stayed for a long time. I kept watching it waiting for somebody to fall in, but no one did thankfully. My street wasn't busy at all and everyone knew it was there.

[blackhatboojum]

Damn nice looking build.

[jjjimi84]

Looks great and it sold quickly!