I was fortunate to make contact with Todd Langer around 1993 in his original shop in Oakland, CA and had him wire up my first guitar rack. He did a minor mod to my MP-1 preamps, offered me his 3TM mod for my ADA MP-1 preamp, and turned down Todd's offer since I wasn't in the know about his 3TM mods or his Marshall amp mods. I just knew he designed the ADA MP-1 preamp and was given a phone number on where to find him. I know my friend, Bob Coons, an awesome jazz/fusion guitarist, still owns his Langner preamp and it kills!
Fortunately, the guys over at the ADA Depot reverse engineered a Langner ADA MP-1 3TM modded preamp and created a better version of his 3TM mod tube circuitboard. I was fortunate enough to scrape the money together and had Bob Metzger (aka Hairston on the ADA Depot) install his 3TM tube circuitboard and fixed all the issues with my MP-1 preamp. I also bought another ADA Depot 3TM mod MP-1 preamp as a spare. I don't own the DCP-1 preamp or a Langer modded Marshall amp head, but I love my ADA Depot 3TM mod MP-1 preamp. It's a shame he quit building/modding amps and passed away a few years ago. Todd was really on to something with his amp mods and amp builds.
Guitar George