There is the Opto plus and the Ultra plus mods Allums does for CS-3. From the description I didn't get is the Ultra plus mod an improved Opto plus design or is it something else. I think I don't like optical compressors. Well I didn't like Diamond comp too much, but this stock Boss CS-3 sounds really nice to me. I guess with Allums mod I will get rid of the noise and gain some warmth, but I don't know which one to choose.. Thanks for the input!