How do you know when to change tubes?

I have a tube integrated amp, to be specific an Audiomat Prelude Reference Mk II. Since I acquired my streaming capability about nine months ago with the addition of a Naim Uniti Core and Audio Alchemy DDP-1, I have been playing music almost every day all day. A rough calculation would be about 1000 hours since I started streaming, but I can’t remember the last time I changed tubes before that, other than it seems years ago. I keep waiting for signs that it’s time to change the tubes. And worrying about it. What sort of clues do you all listen for that tells you it’s time?

You know it’s too late once you reach Mornington Crescent :grinning:


I’ve got a Quad integrated valve amp. When it started making a kind of scratchy, metallic sound when playing music, a bit like mobile phone interference, back to Quad it went, and they replaced the output valves. It was about seven years old at this point, and not used sparingly. Oddly enough the night before the scratching started I remember thinking my system sounded particularly good, so maybe I’ve got tin ears as far as the audible signs of valve degradation are concerned.

:small_blue_diamond:Echolane,.you wrote…“What sort of clues do you all listen for that tells you it’s time?”

:black_small_square:This is hard to know,much like with a cartridge.
It is degraded slowly,…and hearing gets used to it,only when it starts to sound really bad…dynamics poor,lack of energy and may also start to give distortion etc.,so you hear that it is time to change.

Different tubes also keep different for a long time,…it can range between 3-4000 hours up to say 10 000 hours.
Manufacturers usually specify how long a tube lasts,but it can vary greatly.
However,…knowledgeable tube-traders are usually able to test the condition of the pipes.

Otherwise you may have a new set of pipes at home,and quickly test against the old ones.
If the new ones aren’t “burn in”,…you can still hear if it’s time to change.

Had you lived in Sweden,I had been able to help you test your pipes,…but unfortunately you probably live somewhere else.


The best small signal valves, usually used in the pre-amp section can sometimes last for many thousands of hours. However, power amp valves generally have a much shorter lifespan, although it will depend how hard they have been pushed in the design of the amp. For example, many years ago I had a valve amp that used eight EL34s but was nominally rated to output around 40-50 watts per channel. That meant the tubes were hardly ticking over and they lasted a long, long time before needing replacement. If you’re concerned then ask your dealer to test them for you - I assume a dealer in valve amps would have the facility to also test valves.

:small_blue_diamond:Exactly…It’s these that can last for up to 10 000 hours,as I wrote in my previous post.

Also keep in mind that the same tubes,but from different manufacturers sounds different,…there can be a big difference in soundquality.
A savvy tube-trader can probably advise you on this,when you need to change tubes.

You can also get advice on this on various tube-forums,…you soon notice who is knowledgeable on these forums.
Richard mentioned EL34,…it is a normal end-stage-tube,and the difference in soundquality between different Manufacturer can be great.

So ask for advice how different tubes play before buying new tubes.


i have an ear tubes pre. I was told that tubes need to be changed after around 3000 hours. I run nos tubes. In general, for a dac or pre, it’s between 3000 and 10000 hours. For a power amp, it’s 1500 and more.
What are the tubes inside your audio alchemy?

I live in California USA. Unfortunately, it’s a long way from Sweden! The closest I come to Sweden is in ancestry as my father was Swedish. He has names in his family tree like Nilsson, Persson, Svenson, Nilsdotter, Persdotter, Svensdotter, that sort of thing. I also stream a lot of Swedish TV programming via MHz Choice, which I like a lot. I’ve always wanted to visit, but that’s unlikely now.

But back to tubes: I tried to change tubes myself last time and I messed up. I think I harmed some of the sockets in my other tube amp, an Audiomat Arpege, by inserting the new tubes incorrectly. Fortunately I had an instinct something was wrong and I didn’t go on to ruin the Prelude too! I was trying to spare my husband the chore of carrying my 50-60# amp to my Audio repair fellow. At this point, several years later, I would especially wish for you to be in my neighborhood because my husband has slowed down a lot and is really showing his age at 82. I am so afraid he will drop my precious amp.:weary:

I did find the receipt for my output rubes; they are EL34s. Hopefully, I’ll get at least another 1000 hours out of them. But I’ve been a little concerned because volume seems variable all of a sudden. The other day I thought my music sounded way off, though on subsequent days, I’ve heard nothing sounding off.

Oops, Sounds like English humor, which sadly, I don’t understand…

That’s the problem, age has caught up with my husband and I’m a tiny thing, so it’s no easy chore to carry my 50-60# amp into our auto for transport. At moments like this, it makes me somewhat regret investing in a tube amp, though I was a lot younger at the time and the transport problem never occurred to me. Regardless, I love it and am glad to have it.

I’m the sort that could get really immersed in tube rolling, but it’s completely impractical to pursue if I can’t change tubes myself. My audio repair fellow says they need calibrating too, which is just another impediment to experimenting on my own.

:small_blue_diamond:Echolane,…Naturally,calibration…I forgot to mention it.
Two things to consider below…

  1. Knowledgeable tube-traders do this,.they always match the tubes to each other,before they sell any tubes to you.

  2. Regarding Calibration,…Some tube-amps have “Auto-bias”,.then the calibration is done automatically.
    Check it out if you have it on your tube-amp.

But in order not to complicate it to much,…if you have been happy with the soundquality,so buy the same tubes.
I get the feeling when I read your answer,…that you used your EL34 for quite some time.
Also,…you’ve played,you thought…1000 hours only this year.
If it is properly understood,new pipes would be good.
If not your “audio repair fellow” living too far away,maybe he can get past and change the tubes for you,…It doesn’t take many minutes if you prepare a little.

:small_orange_diamond:Echolane,…Great to hear,…and that you see on Swedish TV.
We have a TV-program every fall on Channel 1, which is about American people who are looking for their Swedish roots and relatives.
It’s called in Swedish “Någonstans i Sverige” and is a series of 10 programs every fall.
You may have seen it.

But in sunny California, it’s also pretty nice to stay :wink:.


Actually most Brit’s won’t understand the humour of this either! If you look at “Mornington Crescent Panel Game” in Wikipedia, you will see that it is a non-game with no rules but nevertheless it is played in each episode of a radio game show. The first person to mention Mornington Crescent (tube or metro station) wins, but only if someone else was just about to say it too. So timing is everything…


Hi Echolane,

The Audiomat Prelude is auto bias so you don’t need to buy matched tubes. It is fairly straightforward to replace power tubes as there is a small notch at the base and there is only one way they will fit when inserting them into the socket.

:small_blue_diamond:cat345,…Great that you checked about Auto-bias.
As you say cat345,…EL34 is unable to mount wrong,but if I understood it correctly,…so they were yet wrongly mounted
That is why it is an uncertainty in this,as I understand it.

But Echolane,…buy new tubes,I get the feeling that your tubes has reached its end.
That feeling seems you also have,…otherwise you had not started this thread.
In Addition,…EL34 is quite cheap tubes,.so better to switch more often and have 100% soundquality.



I can usually hear when the tubes on my Schiit Mjolnir 2 are on the way out, the sound degrades quite fast. In th US you have a great choise of tubes much better than the UK, get a new or NOS set and do a roll and see if you hear a difference, match sets of tubes sets are the best and never go down in price.

That is really good news! Thanks much.

Good advice and will do.

As for my other tube amp, the Audiomat Arpege, I did something wrong in inserting tubes and I damaged the sockets on some of the tube sites. As I recall I think I unseated them somehow so it’s tricky now to change them. That tube amp is at my computer and rarely is used now so the tubes don’t need changing very often. Which is very sad because the Arpege has a wonderfully warm tube sound and paired with the Spendor S3/5 Monitors there, music sounds almost indescribably beautiful.

I don’t know much about tubes, but that is one thing I do remember, to get matched sets. But deciding which brand to buy is another thing. I’m just not in a position to experiment and have to rely on the advice of my trusty audio repair fellow. He sold me both my tube amps and his personal listening preference favors analog (LP and r2r) and almost all tube gear, so I tend to trust his advice.

Your answer makes me smile, so that’s a good way to start my day!