Re: DS-1 Mods
The standard DS-1 mod that everyone knows is the Keeley SEM (Seeing-eye Mod) and Ultra. It's available various places on the web if you want to buy the parts and do it yourself. I owned one for a while and found it a big improvement, but a bit... too polite? Subdued? Something like that.
I presently have a DS-1 into which I installed a Monte Allums Recto mod kit. It too, is a big improvemet over stock. I thought it got even better when I put one of the stock diodes back in, in place of Monte's 1N4002. I payed it a bit today - it has a big whompin' bottom, and a fizzy top end that says, "distortion" rather than "overdrive", which is really the whole idea, isn't it? (Not nearly as fizzy as a stock DS-1). It has better picking dynamics and a more transparent sound than the stock pedal, a trait that's shared by the Keeley. The Recto Mod's fat bottom sort of lends a "big stack" tone to a smaller amp, although it's a bit flubbier than a real full stack. With the distortion maxed, it reminds me of Randy Rhodes.
If you want to buy your own parts instead of a kit, look at IndyGuitarist.com - they have several DS-1 mods with sound clips. Look for ErikH to chime in here, too; he gave me a lot of help with mine.