How many hours on BHK preamp tubes before replacing?

Just wondering at what point do most BHK preamp owners replace the tubes? Not sure if it makes a difference what tube you’re running, but I’m using the stock tubes that came with the preamp.


I’m almost at 2000 on my BHK amp and preamp. I’ll probably change them at 5000hrs. I’ve heard you can go up to 10k but that just seems like to many. Lol

Waiting to hear others opinions…

I’m at 1293. A 1000 of those hrs were used breaking the preamp in 13 months ago. Replaced the tubes in the BHK 250 when the preamp was at 931 hrs. So only 362 hrs on the amp.

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5000 hours is about right on small signal tubes.

Here’s a link from Upscale Audio.

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My plan is to replace them at 5k hrs. You can probably go longer, but it’s not very expensive so why not get fresh tubes knowing that the BHK will perform at it’s optimum?

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I replaced the tubes in my BHK 250 a year after I purchased it, and I noticed an improvement in the sound. Not sure how many hrs I had on it, but I’m guessing less than 2000. I know I put a 1000 hrs on it burning it in, plus regular use. Purchased the BHK preamp roughly a year later, so I was then able to keep track of how many hrs I put on the second set of tubes in the 250 over the last year, which was only 362. So now the question is, will the BHK preamp also benefit from replacing the tubes every year, like the 250, or is there a reason why it’s circuitry would be easier on tubes?

Let your ears be the judge. Premium, industrial grade variants of certain tube types, the 6922 for example, were intended for 10,000 hours of life. I’ve never tossed any good pair of tubes prematurely based on a hard and fast rule of thumb. It can even depend on the specific pair you’re using. When you can hear they’re starting to get noisy, replace them. Otherwise, leave a good, proven pair of tubes in your BHK Pre and enjoy.

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That’s the plan. I’ll purchase another set and replace them, and listen. If no change, then I’ll have a back up pair on hand. Just curious what others have noticed on tube life.

That’s exactly what we recommend doing. Generally, you shouldn’t have to think about replacing them before 2000. Once you’re past this mark, do a swap test and see if there’s much change, if not, swap back and keep rickin’ with the old ones.

Though they are fairly low current tubes in the input stage, I’m skeptical if people can consistently get 10,000 out of them.

I like to swap every couple months or 500-600 hours of play. Mostly to mix things up a bit, it’s fun to hear the different signatures, and it’s a good way to check if the current ones are getting near the end.

I have ~12 sets of relatively inexpensive tubes. I enjoy all I keep and sell off those I don’t.

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Depends on the tubes you are using. As noted previously, NOS such as the 6922/7308/CCas have a heater life of up to 10k. Newer mfg tubes much much much less. Obviously, the NOS are more expensive and those of us who have happily dove into that rabbit hole want to get the most out of their “investment.” If in doubt, change out the tubes with a fresh pair of the same and see if you note a difference. I recall Paul noting in an unrelated topic about how his ears got so used to the sound, when he replaced the particular component part he was shocked at the difference, as his ears had grown accustomed to the slowly degrading sound.

I keep a new set of spares of the same tubes.
Once a year, I switch the new ones in. If I hear a difference, I leave them in and mark the old ones as used spares in case one goes bad.