Tube warm up proof?

Maybe it was the "proof" bit that startled people. Any reasonably awake listener can hear that they change as they warm up. It sounds like you're curious to measure how they change- rather than just show that they do?

 

I mean, it probably wouldn't be THAT hard to do a 10 second sine sweep measurement at 2 minute intervals to see whether the actual measurements change over time, and draw a graph based off of the results.

 

I have also noticed my Valhalla 2 sounds better when the tubes are warmed up. Could it just be a placebo effect? Perhaps, however I had my Valhalla 2 turned on for a little over an hour before I listened to some music (I usually just turn it on when I am ready to listen, I usually don't let them warm up for more than a minute or so) - but it certainly seemed to me that after I had the Valhalla on for a little over an hour, the music and sound was much better. Keep in mind, this was before I found this thread so this thread didn't influence me at all, but like I said above, maybe it is simply placebo effect, but to me , it certainly seemed like the Valhalla 2 sounded better after the tubes were fully warmed up. Of course I have no way to measure this or prove somehow that it improved the sound quality, but to my ears, it did seem to make a noticeable difference.

Side Note:

About how long is it recommended to let the tubes warm up to get the best sound from the tubes? Like I said above, except for last night when I had them on for a little over an hour before I listened to some music, I usually just turn it on when I am ready to listen to music, I never really give them more than a minute before I start listening - so what is a good amount of time to allow the tubes to warm up to get the best sound from your tubes?

 

Here are a few notes.

Tubes require thermionic emission to operate, which is provided by the filament heat. As the temperature rises, thermionic emission increases. The tube will continue to change characteristics until thermal equilibrium has been achieved. Several years ago I made some thermal measurements of my Bottlehead Crack as it warmed up. Here is a graph of the data:



For those interested in further information about tube basics this link might prove useful:
http://www.john-a-harper.com/tubes201/

 

Thank you for the info @atomicbob very useful!

 

While I'm not savvy enough to make any statement about how the temperature changes will affect the electrons, and thereby the actual 'sound', it seems that anything more than 30 minutes is probably overkill in terms of warmup time before you can 'enjoy' the bottlehead. 50% of the total temperature change appears to happen within the first 2 minutes anyways, and ~95% within 10 minutes, so 10 minutes is probably a fair 'good enough' point as far as the literal warmup goes. Turn on your tubes, go get a drink, make some popcorn, and then enjoy.

 

Just a uninformed, anecdotal observation, but I've noticed more differences that I'd associate with "warm up" in my desktop solid-state amps than I have with, for instance, the DNA Sonett. Make of that what you will.

Personally, I suspect that such changes are highly dependent upon an amp's overall design, irrespective of whether it utilizes tubes or transistors.

 

Two minutes is just enough time to pour a glass of your favourite vice. Ten minutes until it hits the brain. The timing sounds just about perfect...

 

I don't know if it's the tubes being warmed up or the LSD crossing the blood brain barrier, but my hd650 taste really yellow right now. Much more yellow than they did when I first sat down.

 

Sorry to go off topic here, but is your username a reference to anything in specific?

 

In the old days (1950s) there was no argument about this stuff. You turned on the TV, wireless or radiogram and waited. Never mind the quality of the sound, there wasn't any until all that stuff warmed up. And it took multiple seconds. Or longer with temperamental stuff that could suddenly spring into life when you'd almost forgotten you'd even turned it on. Given this experience, I'm prepared to believe in tube warm-up being a real thing. But then, so is imagination. And so is bias, as in my childhood experience left me still unreasonably put off valves fifty-five years later .

 

I've seen people around here claim that the Jotenheim loses a bit of "glare", after being on for a few days, which I found interesting. I haven't noticed it myself, but I'm willing to believe it, plenty of people with good ears around here who are good at spotting such things.

I tend to give my tube amps about ten minutes to warm up, which is no hardship.. enough time to make a cup of tea and settle in for comfortable listening. The Jot just gets switched on with the rest of the room as a matter of course- so how warmed-up it is varies somewhat. I feel like I should pay more attention.

 

"How do you test the hypothesis that tube temperature affects sound?" This question is probably less important than, "Why would you test the hypothesis that tube temperature affects sound?" Just enjoy some time with your music instead of feeding audiophillic paranoia and time-wasting rituals.

When I had tube amps in the past I usually started listening within a minute or two of turning on the amp. It sounded fine to me and I didn't really notice a huge change in sound while they warmed (with the exception of graphite plate tubes, which "pinged"). Make of that what you will. If you habitually warm up your tubes for half an hour and listen for an hour, you're wasting a third of your tubes' lifespan.

 

The service life isn't a simple function of runtimes, it is a combination of run times and number of heat-cool cycles. You get one heat cycle every time you turn the unit on - whether you run it 30 minutes or the rest of the evening. It is a bit like the lifespan of a lightbulb left constantly on vs. one that is frequently switched. That may be why light bulbs almost always fail when you first turn them on, rather than after they have been on for a while. Other examples of the combination of starting and operating stress include the mileage accumulated by a car that runs "road miles" vs. one used for short trips, or a battery whose life is expressed in number of charge cycles rather than hours of use.

Shiit seems to promote the idea of leaving things powered by hiding the miniature on/off switch at the back of the unit in the middle of a mess of cables.

 

Some of my favourite computers ran for months. Might have been years if they hadn't been turned off and restarted.

 

Why do we even have all these measurements then? Why do we compare the different modded HD650's FR, distortion, and CSD measurements with those of stock 650s? We can clearly hear the differences between them, so why not just enjoy them and forget about measurements?

I think OP had a legitimate measurement request. I think it'd be interesting to see what exactly changes in the distortion and FR graphs between a cold tube amp and a warm one. Just like how we can point to a headphone FR graph and say "see that bump at 7khz? That matches the sharpness of the treble I hear. And that 3rd order harmonic distortion in the bass is making it a bit less snappy than I'd like." I would love to see someone measure a cold tube amp and a warm one and see what exactly changes. And see if we can associate the changes seen in the measurements with the changes we hear.

 

I whole heartedly agree that measurements have value. I also think that it would be interesting to find out the relationship between sound and tube temperature. Moreover, I'd love to ascertain whether or not these differences are audible and the types of people they are audible to. If I could understand the graphs and measurements present on SBAF I'd use them to inform my buying decisions. However, any interest I have in tube warmth would be academic. When I want to listen to music I don't always plan the time and prefer to start listening right away. Call me a philistine or ignorant.

Anyway, never mind me. In case you've not gathered already I know next to nothing about gear. We all need to know when it's time to stop analysing, and just lean back to enjoy our music.

 

Agreed... I just turn my amp on when I get home from work and leave it on until I go to sleep. I listen to it whenever I feel like it and not worry about tube warm up.

 

Unfortunately I don't have a way to take reliable temperature measurements at the moment, although I'd love to try that as a follow-up at some point. My working assumption right now is that time has a strong enough correlation with temperature to be useful. I currently have about 15 data points but I realized I wasn't playing any music between tests so the tube might have cooled during that time.... I'm hoping to be able to get enough data (and analyze/organize it enough) to be able to post some results this weekend. Schedule's a bit tight at the moment, but fingers are crossed!

 

Yes, enjoying music is a given. And of course, measurements and answering questions are academic (we're doing it to satisfy our curiosity). But I really don't think this kind of measurement is something that falls in the realm of "it's time to stop analysing, and just lean back to enjoy the music." It seemed like your other post was discouraging answering the question "What are the measurable changes of warming up a tube amp?" but I get where you're coming from now.