We've sold vintage tubes on 'bay for a decade (tekdesinc) and also are designing high-end tube gear. There's 4 categories to this question:
1. raw new modern small signal tubes: definitely breakin for 100-200 hours depending on brand. If cryo'd halve the time. (cryo is a good idea BTW as the thermal exercise also linearizes the raw metal structure).
2. raw new modern power tubes: this is difficult as you don't want to burn their limited lifespan so breakin for 50 hours until critical listening +/- 50% depending on brand. If cryo'd halve the time.
Next 2 are for vintage tubes as they are rarely unused, typically 95% are used and already 'broken in' per se.
3. vintage small signal tubes: since these have probably been sitting around, breakin for 10-20 hours depending on brand. Sylvania, RCA, GE require 150-200% more time as they have commercial alloys. WECOs rarely need more than a couple of hours before listenability, but like wine they age nicely.
4. vintage power tubes: again this is difficult as you don't want to burn their limited lifespan so breakin for and hour or two. Always warn power tubes an hour + before listening to avoid severe stress to the metallurgy.
1. raw new modern small signal tubes: definitely breakin for 100-200 hours depending on brand. If cryo'd halve the time. (cryo is a good idea BTW as the thermal exercise also linearizes the raw metal structure).
2. raw new modern power tubes: this is difficult as you don't want to burn their limited lifespan so breakin for 50 hours until critical listening +/- 50% depending on brand. If cryo'd halve the time.
Next 2 are for vintage tubes as they are rarely unused, typically 95% are used and already 'broken in' per se.
3. vintage small signal tubes: since these have probably been sitting around, breakin for 10-20 hours depending on brand. Sylvania, RCA, GE require 150-200% more time as they have commercial alloys. WECOs rarely need more than a couple of hours before listenability, but like wine they age nicely.
4. vintage power tubes: again this is difficult as you don't want to burn their limited lifespan so breakin for and hour or two. Always warn power tubes an hour + before listening to avoid severe stress to the metallurgy.