How are tubes to be purchased in general?

I'm not familiar with the biasing process for Rogue amps but some amps have a bias trimpot PER TUBE (CJ) which makes tube matching less critical. My ARC VT100 MKII amp had just one bias trimpot PER FOUR tubes. In this case tube matching is more important.

You can buy matched pairs or matched quads from most tube dealers or just a single tube. If just one tube blows, I would probably buy a matched pair anyway and just keep the spare handy. Over time, you'll probably own several sets of tubes anyway! I have KT-88's and 6550C's that I like experimenting with. It's part of the fun.

As for expense, in all honesty I have never had a tube blow or wear out on me yet but I've only been playing with my tube gear for about 1 year. Even if you had to replace ALL your tubes in 1 year (not likely) thats a small investment compared to the quality sound you'll enjoy with tubes.

I've tried ARC VT100 MKII, Conrad-Johnson Premier 11a, Classe CA-200, Classe CA-300 (bought and sold used). So far I like the CJ the best. And so far I still like the original 6550C tubes. Have fun!

Agree with the posts above. Nice to measure the voltage (bias) running in your tubes - get a meter. The only time you are going to run into trouble is if your tubes are running hot and some amps change over time. Not like Sand amps where you plug them in and never think again for 10 years. Get to a local club or post on the audioasylum.com tube section. Someone will have your amp and will be able to tell you just how to take readings and what they should be. I think you will find the audioasylum site invaluable if you are new to tubes.
Good Listening!

Over the last 7 years I've owned two different all tube setups and I've had it pretty easy when it comes to tubes. I've never had a failure and the tubes were not expensive. I have Rogue equipment now and the amps are auto biased (you don't do anything). My only qualm with tube amps is that they produce a lot of heat in the summer. A small price to pay. Btw, I just purchased two quads of Electro Harmonics 6550 tubes from Triodeelectronics.com for $99.90/quad as an upgrade. The original tubes still work fine. I'll test the new tubes in a year and if they're ok then keep on truckin with them.

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.

i'll try and help--i dont own tube hifi but ive owned lots of tube guitar amps over 20yrs..
if a output tube goes early on deffo check the bias and change the tubes in a QUAD i wouldnt just change one---if ya cant find a quad buy 2 matched pairs and put one tube from one pack in first then next to that put one in from the other pack soforth---i change my power tubes once a year frequent use if i use the amp more than usuall in a year i change them in 9 months time.......
pre amp tubes last a lot lot lot longer so you probally wont want to change them unless you feel you must(anyways they aint exspensive unlike pwr tubes)
check out a guitar magazine/paper called ''vintage
guitar'' and there are so many ads from places that sell all sorts of tubes in quads pairs ect JJ,SOVTECK,SVETLANA, ECT ---in my own experience i thought the russian tubes sounded a bit better than the chinese tubes like RUBY...
some help maybe..cheers