Contact Oritek audio, Stuartbmw3. I just got back my modded ST 70 last week. Ori replaced the whole board, disabled the ultralinear mode, and made it a Triode(single-ended)with 18 watts. He uses no feedback. The live feel of the amp is fantastic! His price is the best also(You should hear his pre/dac, which beats many $3000 preamps.). It's all discrete components. In fact, I tried to put a review(sort of)of his Stereo 70 over the weekend on Audiogon. You can't go wrong with his amp. Please give him some time to work his magic, as he usually doesn't offer this work. As I remember the Stereo 70, this doesn't sound like it. It is very detailed(more than my Nuforce's), dimensional, fast-it just sounds more like music than what I am used to.
ST-70 modifications
I tried a search, but had surprisingly little luck in finding info. I have a stock Dynaco ST-70. I am looking for opinions on what mods are recommended. I am thinking Curicio, Welborn/Kimmel, Van Alstine, Triode Electronics....etc. Looking to replace the driver board and the quad capacitor at a minimum. Thanks for your input