How often should I change tubes based on hours used? I am using 7dj8s in both. Thanks!
Depends on the individual tubes but 10,000 hours for input tubes is not unheard of. Best way to know if they are ‘done’ is to swap them and listen.
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Buy spares. When your existing tubes don’t sound as good as your spares, leave the spares in.
Repeat every 5000 hours.
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5000 hours is a good estimate, although as Brett said you can get 10K, especially with 6922, or 7308. A factor in longevity is how good the tubes were they when you installed them. A set of pulls would wear out more quickly than unused NOS.
When the tubes sounds less crisp (muddy), install your replacement set and compare. It should be evident.
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Let your ears, rather than hours on the clock, be your guide. When you begin picking up the usual symptoms of a pair of tubes going south, elevated noise floor being one, replace them. My experience is a really good pair of tubes can be hard to find and, depending on your preference for NOS or new production, expensive. I decided a long time ago I’m not going to retire a great sounding pair of tubes based on some hours of use rule of thumb, especially if they’re exhibiting no evidence of distress. One other point to consider, the number of hours of use you get out of any pair of tubes can be dependent on tube to tube variations during manufacturing. Tube ratings, such as the canonical ‘10,000 hours’ for 6922s, should be thought of as only a rough guide. Not gospel.
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Thank you for the help. Using 7dj8s now - got them from Upscale but Kevin now won’t sell to anyone who didn’t buy gear from him. I found 6 elsewhere and ordered for future use. So far all sounds great!
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Matsu Nationals? That’s a nice 7DJ8 variant.
I have a set of those, they sound fantastic in the BHK 250 and just terrible in the BHK preamp.
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Refreshingly good answers, everybody!
Burger - I can only guess you weren’t buddies with your recording engineers back in the day 
The Talent…
I use them in an Audio Horizons tube buffer. Pretty much any 6DJ8 variant works.
Beefy, why do you say that?
Hmm , interesting. I had 1700 hours on my pre and it was suggested by at least one if not two PSA folks to replace them. No issue, I got new tubes and some peace of mind and as a bonus they are not really expensive. I kept them in case of immediate need in the future… I guess it’s not an exact science by any means.
Sorry - weren’t you a Voiceover guy? The 'ole memory ain’t what it used to be.
Most of us love NOS tubes. The tubes in my Decware amp are roughly 50 years old and they sound great, just as I was hoping. And they were checked, matched, certified delightful by Steve, the man himself. But they’re friggin old. And the MTBF (mean time between failure) can’t be calculated because of their age, only predicted—to last at least until breakfast. Hell, at 71 my MTBF is not much better. So I keep spare tubes (and I eat salmon and salads). And I don’t flip out when the tubes sh$$t the bed, so to speak. Keep spares.
Tubes are an artifact of passion. And with passion, you give, you get.
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I was and am. But don’t see the connection to the guys you mentioned?
My best,
Bob
I was suggesting that, as a longtime voiceover artist with studio experience, you would have known about tube life.
But y’know…The Talent tend to be out of touch with regard to these things. Waltz in and do their thing and leave us to make it work.
Ah, NOW I get it.
I always wanted to get there early and check out the gear. But that isn’t the gig. Lanes. Stay in your lane.
My best,
Bob
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You haven’t become your own engineer? Been a long time since I had to have a VO guy go to a studio or come to mine.
Oh yeah – studio in home – Neve powered.
Back in the in-studio day, I never wanted to leave – wanted to hear the spot/project come together, wanted to hang; but, esp in LA, it was job done, thank you bye!
My best!
Bob
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