If you have read our webstie then you probably know that we have an AD30HTC in the studio and this is Bob's favorite for preamp tubes paired with JJ EL844's. This kit uses a matched quad of the JJ EL844's and a JJ GZ34 for power. For channel one we use a gold pin long plate ECC803S for V1 and a balanced gold pin ECC83S in V3. In the second channel we use two gold pin ECC83S's with one balanced for V4.