I see three identical current sources (per channel), but I haven't designed with those FETs so I don't know what current they are set at. You can look up the tube data sheets to find the heater voltage and current draw. Here is (I believe) the most popular tube data sheet locator:
http://tdsl.duncanamps.com/I have some misgivings about the RIAA, but it's not my design and I don't have time right now to study it carefully.
