Here's my version of analogmans DS1 Pro mod. Although baligtad kami, my mod currently is only implementable on Taiwan-type DS-1's, while his is applicable only to Japan and early Taiwan-type DS1's. In time, after I put in more research on the pinning and other parameters for the Japan DS-1, I can then implement this on Japan DS1's. However, those things are really rare these days, so maybe it won't be worth it too much.
It involves, among other things, placing a daughterboard that carries a higher quality IC chip, my favorite high-impedance input IC which is gorgeously sensitive and does emulate the sound and player response of a tube amp. The daughterboard covered in masking tape is the one that carries the chip. You can also swap it out with other chips like OPA2164's or NE5532's depending on your taste.