How are tubes to be purchased in general?


I have never had a tube power amp. Although I have a tube preamp (AI3) it is relatively unfussy with tubes. If a power amp has a matched quad set of tubes, how do you replace them if only one goes bad? Most are sold in matched pairs. How many do I have to keep around for emergencies? Do all four ever go bad at once, or can I just pop in one or two. I talked to the manufacturer (Rogue) but the rosy picture of tubes lasting years finds me a little bit skeptical. Of course if this question is like an owner of a gas guzzler car wondering if he can afford the gas (tube replacements) please tell me so or to go get a SS amp. It's just that a cheap pair of matched KT88's/6550 go for about $70.00 new, two monoblocks mean 8 tubes so that is $280.00 investment.
drjjpdc

Showing 1 response by emfoods0d89

If you are careful and don't do anything stupid (hooking up speakers to a powered up amp...) then they will last you years. I have a bunch of amps with very old tubes. My EAR amps got 10 years out of the tubes without ever blowing them. After some time, the sound lost some dynamics and it was easier to distort at loud volumes. I tested the tubes, ended up replacing them for very little and expect many more years of use. Try www.tubesandmore.com or www.thetubestore.com to get an idea on tube pricing.
By the way, it is best to replace worn output tubes in pairs/quads. You also want to make sure that both channels have the same quality tubes or you will notice a difference. Tube biasing helps but, if you push them hard the older tubes will stand out.