How often do you change your output tubes?

[Shark Diver]

I go with my ears. Ya ya, they're typically deaf in the grand scheme of things - but if my amps start to sound like they're lacking in sizzle, or bottom end, or the frequencies that made me love 'em to start with; and I find myself squeezing more and more out of the EQ/preamp to get the amp to a certain place - it's glass time.

You mean you don't try new pedals, cords, guitars, amps, speakers, cabs, etc... Where's the fun in that?

 

[spirit7]

I go with my ears.

That said, my Mark IV hasn't had new tubes since 1994 (previous owner, bought by me last year) and still ROARS \m/ !

-C

 

[rupe]

Just listen to your amp. Does it sound different? Less forceful, less dynamic, lack of clear highs, presence of flubby lows, dull sounding in general? Replace your power tubes. As much as people would like to make it a scientific phenomena (and it is), your ears can cut through all the "tech talk" and tell you what you need to do.

That said, tube life will vary greatly depending on the amp (all else equal). I can get a year or more out of EL34s in a Marshall type amp, but those same tubes will only give me 2-3 months in my Matchless Chieftain.

 

[MississippiMetal]

That said, tube life will vary greatly depending on the amp (all else equal). I can get a year or more out of EL34s in a Marshall type amp, but those same tubes will only give me 2-3 months in my Matchless Chieftain.

That depends on hours used, How cranked you typically run the amp, B+ voltage and bias-point. It's not simply an "amp-to-amp" comparison. Now that being said, the Chieftain was NOT designed to maximize tube life. In fact, it was designed to basically eat tubes in favor of the almighty tone. If you can afford that kind of valve turnover, cool. I like mine to last a little longer than a few months, personally.

 

[blackba]

I go with my ears.

That said, my Mark IV hasn't had new tubes since 1994 (previous owner, bought by me last year) and still ROARS \m/ !

-C

MarkIVs are easy on tubes, as they are usually biased pretty cold. Although my mark IV has gone through 2 sets of 6L6's since I have had it (about 10 years), but mine has a bias pot.

As to the original question, if you are worried about the power tubes, swap in a new fresh pair every 6 months, if you hear a big difference in tone, then order another backup set and get rid of the old tubes. If you don't, then put the old tubes back in and run for another 6 months, than repeat the process. Pretty soon you will get an idea how long they can go.

 

[supersonic]

Just reporting back. Had my tubes changed by my tech. They definiately were worn, sounds much better now.
It's a Friedman Marsha 100w JJ EL34s' FWIW, tubes were 18 months old. Think I'll change them again in 9 months.
I'd like to be able to change my own, my tech says he runs them for 24hrs to burn them in, then re checks the bias.
Is it something that you guys do yourself, or just leave it to the pros?
Thanks for the input.

 

[rupe]

That said, tube life will vary greatly depending on the amp (all else equal). I can get a year or more out of EL34s in a Marshall type amp, but those same tubes will only give me 2-3 months in my Matchless Chieftain.

That depends on hours used, How cranked you typically run the amp, B+ voltage and bias-point. It's not simply an "amp-to-amp" comparison. Now that being said, the Chieftain was NOT designed to maximize tube life. In fact, it was designed to basically eat tubes in favor of the almighty tone. If you can afford that kind of valve turnover, cool. I like mine to last a little longer than a few months, personally.

Which is why I said "all else equal" and based my comments on the OP's statement of "amp that gets used regularly at gig volume".

 

[Laars]

I'm with the other answers of, " my ears usually tell me". You'll start changing your settings to compensate, which is a sign you need to change them. If I miss those signs, one will die in the middle of a gig. Guess its why I like multiple amps live, and I keep spare tubes with me. Tubes are why too much money to just change based off of time alone.

My amps only go to my amp tech when I'm changing types of tubes or range of the tubes. If I stick to the same type, and range# (groove tubes) I don't bother with having it re biased every time, and just change them myself. When I fire up the new tubes, I pay attention to the center of the tube and look for red-plating or a "cherry" plate glow in the middle of the tube. This will happen when a tube is incorrectly biased, causing the plate to overheat. This shows the bias is way off and will not last long if rebiasing is not done.

The Tube store has a good article on this. http://thetubestore.com/blueglow.html

photo from the tube store article.

Guess its why I've been stuck using Groove tubes. I can change tubes, and not worry about spending $80 on a rebias if its not necessary.

 

[blackba]

Just reporting back. Had my tubes changed by my tech. They definiately were worn, sounds much better now.
It's a Friedman Marsha 100w JJ EL34s' FWIW, tubes were 18 months old. Think I'll change them again in 9 months.
I'd like to be able to change my own, my tech says he runs them for 24hrs to burn them in, then re checks the bias.
Is it something that you guys do yourself, or just leave it to the pros?
Thanks for the input.

I bias the amps myself using a compubias, but I also have a background in electronics (not in tubes unfortunately). IMO its worth getting a set of bias probes and knowing how to check the bias.

 

[MississippiMetal]

I bias the valves and burn them in at idle for a minimum of two hours to allow them to adjust to the operating conditions of the amp, periodically checking for signs of trouble (red plating, significantly drifting bias, etc.) At the end of the burn in, I check the bias again, if it's drifted more than 7mA in either direction, I'll adjust it and leave them for an additional half an hour to see if it drifts again. If it doesn't, good. Amp is ready to roll. If they do, then I know I need to keep an eye on those tubes in the coming weeks to see how they are going to hold up.