I am a bit fanatical about the DS-1 pedal all the sudden. They kept sending me made in Japan and made in Taiwan models with the rare diodes and op amps, that just sound great. But finally they sent one with the shitty Mitsubishi op amp so it's time to do the Keeley mod.
This post is a disambiguation. There are a lot of online "tutorials" bout how to do this Keeley mod yourself, but there's a lot of vague information about the clipping modes.
After an afternoon and evening of sleuthing and experimentation let me say this. The "SEEING EYE" mod is simply replacing one of the stock dioes with a 3mm LED which is visible on the "TONE" word on the case, you drill it out with a 1/8" bit, and glue it in, and that's the SEEING EYE mod.
The ULTRA mod is the switched part. With the switch in the "up" position this second diode is the stock diode, a 1N4148. The "all seeing eye" glows brightly, and the sound is very similar to the standard BOSS DS-1 tone, but with Keeley's wonderful refinements. When the switch is down, you put a second 3mm LED in series with the stock 4148 diode, for the "ULTRA" mode. The Ultra mode is the down switch position and there is a diode in series with an LED for the second clipping diode only. Along with the standard Seeing Eye mod. The Seeing Eye glows less brightly in this down switch position. The sound is much, much louder and the clipping is reduced, along with more bass frequencies being heard.
So to wrap it up, the first diode is permanently replaced with the Seeing Eye 3mm LED in the TONE text, and the second diode is replaced with a switching array that allows to you to go between the regular stock 4148 diode. And a second position (down) which gives the Ultra mode of a 4148 diode in series with a 3mm LED which is not visible, it exists inside the case.
This is a wonderful modification for the shitty newer $20-30 DS-1 you can find used with the annoying sound. The older Japan and Taiwan models with the Toshiba op amps should not be modified, they sound wonderful. But with this Keeley setup, the newer DS-1 can sound each bit as good. I especially like the Seeing Eye mode. The Ultra mode is a bit off-base from how a DS-1 usually sounds, so I will have to find a use for it. I am guessing it could prove useful as a bass guitar distortion. The Seeing Eye mode is more of a general refinement of the stock DS-1 sound.
You can see my photos below for the pedal I modified, and the full list of Keeley mod instructions on a piece of notebook paper. I also would recommend trying an older Japanese style DS-1. I would also recommend the Wampler mods that are available online in instructional form. I did the "JCM" and "18 Watt Marshall" mods and they are both pretty cool. Now I have to pick a favorite! Or not... I have 5 orange pedals sitting here now!