How many hours do you get from your Ref 10 6550 tubes?
 

How many hours do you find you are getting from the 6550 tubes in your Audio Research Ref 10? When did you decide to replace them?

(mine sound great after 2500 hours which seems surprising, though half those hours are idle).

Fwiw, the manual says: "The vacuum tubes inside your Reference 10 are quality tubes and with normal use should not need to be changed for approximately 4,000 hours
of use."

Sometimes we don't recognize gradual changes occurring over time. Did you swap in a new pair of 6550s to compare to the one's with 2500 hrs on them?

I did. At 2500 hours they haven't lost anything compared to new ones.

What are others experience?

My Ref5SE manual also has this statement this but does it refer to the 6550 or the 5 6H30s ? - or both ? I read somewhere the 6550 should be changed more frequently.

I have more experience with this now. It depends a bit on how resolving your system is but most 6550’s will lose their pizazz after 1000 hours. It’s critical to have a fresh set to determine if you should replace them. Swap in the new after 1000 hours and see if you hear a big difference. If not, stay with the old until you do

Where did you get your 6550's. ARC? I have heard good things about Jim McShane, but never bought from him. Thanks.

I bought from him several times. Jim McShane is a reliable tube dealer.

6550 in Ref 10 is critical in forming the final sound. I have tried around 10 different 6550’s. The best is still Tung Sol old tubes. The black plate is top of my list. The tubes tend to degrade around 2000 hours. I have used up a few sets already.

I see a pair of 6550 NOS, NIB for $440 on ebay. I have no experience buying these thing from other than dealer/manufacturer. Anything I should be aware of? Thanks.

Be careful. If you are not expierenced in buying NOS tubes, stick to a known reputable dealer.