One of the drawbacks of tubes is that they need to be changed after a certain period - going from 1000 hours in some tubes to 10000 hours for others types, sometimes depending a lot on the equipment.
How do you check for the need of tube replacement in your system?
I have a home made dynamic tube tester and check mainly for transconductance - I measure it and record it when I buy new tubes, but sometimes I feel that I am replacing the tubes before it is needed. Modern Audio Research equipment have an hour counter and advise to replace after a typical use of 4000 hours for signal and 2000 hour for power tubes.
Some people advise to check for variance of plate resistance, but I could not find any evidence of correlation between its variation and tube life.
My VTL MB750's tubes last longtime. As they have B+ fuses, time to replace the tubes is easy to establish - the first two time it blows a fuse I replace the faulty tube and fuse, at the third fuse I know it is time to replace the twenty four 6550s ...
How do you check for the need of tube replacement in your system?
I have a home made dynamic tube tester and check mainly for transconductance - I measure it and record it when I buy new tubes, but sometimes I feel that I am replacing the tubes before it is needed. Modern Audio Research equipment have an hour counter and advise to replace after a typical use of 4000 hours for signal and 2000 hour for power tubes.
Some people advise to check for variance of plate resistance, but I could not find any evidence of correlation between its variation and tube life.
My VTL MB750's tubes last longtime. As they have B+ fuses, time to replace the tubes is easy to establish - the first two time it blows a fuse I replace the faulty tube and fuse, at the third fuse I know it is time to replace the twenty four 6550s ...
