Re: Tell Me About the Boss SD-1
Boss got this right a long time ago.
C6 mod does add some treble but to my ears it is definitely not an improvement. It just adds white noise in the highs.
Changing c3 can add some bass, but the more bass you add, the looser and woolier it gets.
Increasing the gain reduces the bass, so if you double the gain, you also need to double the bass to get it back to where it was initially.
The other downside of adding gain is that you can end up with the "bypass bleed" thing that people complain about.
BAsically, boss got the recipe right.
HAving owned both vintage boss od-1 and sd-1, i actually prefer the sd-1. I dont know how or why, but it is punchier and less compressed than the od1. Also, ABing a vintage sd-1 with a fulltone fulldrive (basically a hod rodded sd-1) believe it or not, the original sd-1 just hands down slays it. Ive been a fulldrive user for many years and its a great pedal, but just put the two side to side, ignore your bias about true bypass, mosfet mode, flat mids and all that extra stuff. Ignore your USA made bias. Ignore the boutique cred and use your ears. The SD-1 is the all time champion. Easily.
So yeah SD-1 = win.
I even prefer it to the much raved about 808 tube screamer and the analogman brown and silver mods. I prefer the stock vintage sd-1 over any of the mods ive done myself including some kits from monte allums etc.
Basically, roland threw a ton of money into research and development back in the day and they got it right. The buffer works. The knobs are out of the way of your toes. The pedal even feels good and doesn't make a popping sound. Hell, they even worked out that assymetrical clipping sounds great so they patented it before ibanez built its first tube screamer. I love tube screamers too, but prefer the boss. Its the business for working musicians. 
Caveat...its been a while since ive used one of the new taiwanese sd-1s, but given that there is pretty much no change to the circuit im sure they are just as good as the old japanese ones.
Bone stock, vintage boss sd-1 is something you will have to pry from my cold dead fingers.