Thanks for kind words and for your understanding, Analogguru.
And thanks for the great mod. I'm off to test it on a Marshall JCM800 and with humbuckers, and I expect it to perform impressively in that setup.
First, the difference between a stock SD-1 and this mod is (IMHO) a large one. I've never heard a stock SD-1 before this one came to me, and I didn't quite like it - "unflexible" sound, that's how I've heard it. Pretty harsh. OK as a tube amp booster ("Drive" at minimum, "Level" cranked) and that's about it.
Enter this mod. As I prefer red LED diodes in the clipping stage, I find that this configuration brings out "the good" in them, in an almost exemplary manner. There's that "nice fuzz" in the bass part of the tonal spectrum, there's that dynamic in the sound (play soft and they will be almost imperceptible, hit the strings hard and they will start to "cut"). Compared to my Turbo Rat, there's more mids, in a good way (just about enough, any more and the pedal would sound less transparent). Overall, the sound seems much "softer" and "bigger", it "flexes" more, and "the color" of the note changes as it drops. Now the pedal "thickens" the singlecoils nicely and takes you to the "Marshall JMP Rock God" land with "Drive" cranked.
I wish I had the time to "clean" the power filtering a bit - I find this pedal, as well as a lot of Boss pedals, "on the noisy side" when compared to any DIY booster/overdrive which has, say, a couple of strategically placed tantalums and metal-film resistors - so I'll have to see how prominent would that amount of "Boss hiss" be in an live setting. If I have to guess, I'd say it'll be manageable, especially with humbuckers.
Overall, a nice, just-about-enough-sharp, thick rock drive which is "on the civilized side" (ie. not too much distorted), and a very "ear-pleasing" one in that context. Like a bodybuilder with a tie. Bruce Wayne of the pedal world.
Yeah, as soon as I've seen the mod (developed by Analogguru, with red LEDs and so on) I knew it'll be at least a good sounding one, and it turned out in a "I can see why someone would pay $1000 for that sound, if he wanted an ear-pleasing rock drive".