GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Melquiades Amplifier
In the Thread: Is it the time to change those tubes?

Post Subject: Is it the time to change those tubes?Posted by Romy the Cat on: 10/2/2011

I do not have a lot of equipment that uses vacuum tubes I have a phonostage and power amp that are tube based. The phonostage used 12AX7 that in there from 1999 and I think they will survive me. The power amp use gas tube 0A2, the output triodes 6C33C/YO186 and drivers 6E5P/6E6P. Dealing with tubes I kind of always in defense about the state of the tube and I do not know when to change them.

I do have tube testers and can measure anything miserable. In some cases I observed that mutual conductance, cathode emission of pate current were gradually lowering and it was reflecting that the tube get weaker. In some case I have seen that the same type of the tube after a lot of working still hold the specification as it was brand new, just taken out of box. And I am taking about the tubes that have seen a lot of use. My power amps run a lot and the 6E5P/6E6P driver tubes are used in there not in very spearing way – at 7W on plate. I have seen some tubes that looked absolutely fried but worked, sounded and measured perfectly. I always in defense what to do with them.

My initial idea was to put time meter in the power amps in order to monitor how long the tube work. Sine I have 6 channels and 11 tubes in each amp with different degradation rate then it does not appear too practical to me. I keep a log where I wrote when I replace each tube. It was useful and I was trying to get a year from a tube. Then I abandoned the log as getting more experience I can very accurately estimate how long the tube worked by evaluating the density and character of darkening glass on the tubes sides.

Still, the initial question still remains not answered. What to do with the tubes that worked own period and still perfectly operational. I was not able to see any sonic differences or any other advantages to change them. What is your take on the situation?

The Cat

Rerurn to Romy the Cat's Site