Ironic and timely that this thread has been resurrected. I am planning to replace the ARC supplied 6550 WE tube in my PH-8 phono pre. The 6550 WE has 2000 on it and its time. Not having read this thread, I went ahead and bought a "modern" Tung Sol 6550.
I realize this thread is about the Ref 3. As stated, I will be rolling the PH-8 PS tube. I'll report back with my reactions. Just thinking out loud -- I wonder if the 6550 PS tube in the PH-8 phono pre makes as much difference as tube rolling in the Ref 3.
Btw, I used to own the Ref 3 and have since swapped it for the Ref 5 and then the Ref 5 SE. I mention this because I think the Ref 3 was and is a **great** linestage. IMO, while somewhat different sounding than the Ref 5 (not SE), both are (were) great linestages. I think the SE upgrade does take the Ref 5 to another level, but I gotta tell ya -- the Ref 3 is a classic.