2. amps-preamps
  3. 157326-90616

Tube Rolling

When do you change tubes on amplifiers? Bought an Audio research VSI60 used 18 months ago. Have no idea the age of these tubs. Think the amplifier sounds good but maybe there is more sound hidden? How do you know if drive tubs or power tubs need replacing?
titus1
tuberist
951 posts
 
Titus, 6550 power tubes, correct? It's always a good idea to have a spare set on hand...you never know.  So, try some new 6550s and see if you can hear a difference and like it. Tubes take a little burn in time, IMO these are probably "settled in" with 50 hours or less of play. Let us know what you do.
titus1 OP
18 posts
 
Today I use Tung Sol KT 120. 6550 and KT88 also fit.


millercarbon's avatar
millercarbon
12,531 posts
 
Nice amp by the way, very similar to mine. I change tubes when they blow, start acting up (funny noises) or sometimes just when they're very old. One set went a good 3 years, maybe 4, in my Melody. https://systems.audiogon.com/systems/8367  That one time the dynamics did improve when the new tubes went in. Not like it seemed to lack before, but it was noticeable with the new tubes. This only happened that one time when the old tubes were very, very old. 

Different brands have been used over the years. JJ, Svetlana, Sovtek, Tung-Sol, Electro-Harmonix, basically all of these except the GE https://www.thetubestore.com/power-tubes/6550-tube-types The Melody uses KT88 and before that I used KT88 and 6550, they are very similar with KT88 being just a bit more liquid and deep. JJ is the most liquid and deep of the others I have tried. Even so not a lot of difference even from the best to the worst. 

Early on, because of all the stories, I tried replacing tubes that didn't need replacement. What people call tube rolling. Tube rolling is buying tubes you don't need to buy. Which I can understand the attraction to calling it tube rolling. Tube rolling rolls off the tongue way better than buying tubes for no good reason. Anyway I did try buying tubes for no good reason. Which is how I know that's what it should be called. Its not that there isn't any difference. There is always a difference. But for the same amount of money you could buy an Orange Fuse and have it be not merely different but incredibly better, and with money left over.  

Also there seems to be no correlation between what you pay and what you get. I have had the most expensive tubes sound bad and blow in a week, and I have had the cheapest tubes sound the best and last forever. And everything in between. Tubes are like records- you pays your money and you takes your chances. 

This is all power tubes I'm talking about. 6550C and KT88. Not that it makes much difference. They sound different yes but in the big picture what matters is power tubes get replaced because they wear out, while input tubes get replaced because, well you tell me they seem to last forever. 

Putting it all together, for you with a used amp the smart thing to do is buy a new matched set of power tubes. I'd go with JJ they're the best value in my experience, both in terms of sound quality and reliability. If you are really into it get a set of input tubes for the same reason, to have a spare set. Also who knows they may sound better. (Or not.) Either way now you have a spare set which is what I have come to see as the main benefit of the whole exercise. 
More to discover