Earthquaker Devices Grey Channel

This is the 400th layout on the blog. Kinda hard to believe I've drawn up that many. O_O

The cool dudes from Akron cooked up the Grey Channel, a dual overdrive based on the classic grey spec DOD 250. The 250/Distortion + circuit is one of my favorites and it turns out it's one of EQD's favorites as well:

It is based around a classic hard-clipping gray box overdrive (subtle hint, huh), one of my all-time favorites. Coincidentally, this is the very same pedal that got me started building pedals and launched EQD. It is two channels of a simple hard clipping overdrive that leaves the character of the guitar and amp intact. The Gray Channel retains the classic warm overdrive sound and expands upon it with several clipping options and bigger bass response. Each channel has 3 clipping modes. The Green channel- “Si” (Silicon clipping diodes), “Ge” (Germanium clipping diodes) and “N” (no clipping diodes). The “Si” mode will be bright/loud/fuzzy and has a natural tube type break up. “Ge” mode is a little looser with more lows and warmth and less output. “N” mode acts as a clean boost until you hit roughly 1 o’clock on the gain, at which point it’ll start to saturate the op amp into a biting, loud distortion. Phew! Still with me? Cool, onto the modes of the Red channel. Here, you’ve got “LED” (LED clipping diodes), “FET” (Mosfet clipping diodes) and “N” (again, no clipping diodes). “LED” mode is the loudest, cleanest and most touch sensitive/least compressed. “Mos” mode is the most compressed with a tighter crunch; the biggest hesher of the group. And finally, the “N” mode is the same clean to crazy loud op amp distortion set-up as the Green channel. With a couple of switch clicks you can go from your bypassed tone to warm break up to over-the-top gnarly grind and any/every combination in between.

Using the above info from the EQD product description, I've come up with a work-a-like to the Grey Channel. Using the Grey Spec 250 schematic as a base, I drew up 2 of them using a single 1458 IC (a dual version of the 741), increasing the value of the input capacitor to 22n (feel free to adjust that to taste) for extra bass response and including the various clipping options outlined above. I also changed the value of the gain pots from C500k to B1M, which is a fairly common mod to 250/Disto + circuit.

You can wire two separate on/off footswitches if you want, but if you want to wire it like the original with a master on/off and then channel selection, wire it like this:

Connect X to X and Y to Y. If you want to use a bi-color LED in place of D2-3 you'll need to wire it like this.