Tube warm up proof?

I've often heard people say that tube amps need to warm up before they can reach their full potential, but I'm wondering if anyone has any measurements to back up that claim. It seems like if it were a real phenomenon than it must manifest itself in some output response of the tube amp (frequency response, distortion, etc). As far as I can tell, no one has posted any measurements of a tube amp over time (immediate, 5 min, 10 min, etc) which could easily support or debunk this common belief.

I am currently trying to conduct this experiment myself using RMAA and my Vali2 with an Electro-Harmonix 6CG7 tube and at some point in the next week or two, I will probably post my own results either to this thread or in the unsanctioned measurements.

Edit: I didn't realize how much people would get caught up on the "debunk this common belief" stuff. The purpose of this thread was more to try to gather specific information about the effects of tube warm-up time on performance characteristics. ie, I was trying to see if anyone else had taken these measurements and found any interesting correlations between warm-up time or tube temperature versus things like frequency response, thd per frequency, impulse response, etc. I was just hoping to drum up responses by making it sound like a "myth-or-fact" proposal, so that's completely my fault. Apologies for the lame headfi style call-to-action.

 

Ok

 

Don't know about measurements but the argument is easy enough to understand. Tubes have a filament that needs to be on in order for the tube to conduct a current. The amp will literally not work without this filament on. Without a fully warm filament you will not get enough current, which is why you want a tube amp warmed up.

There are some tube amps that allow you to turn on the heaters and high voltage supply separately. However I don't know if I would do the experiment. I have heard of electrical arcing occurring when the HV is on before the tube is fully warm.

SS amps have a bit more doubt to me but tube amps needing to warm up is uncontroversial in my opinion.

 

Ah, don't worry there are already folks who've been awarded the Nobel Prize for their work in demonstrating the temperature dependence of emission current density. And don't let the Vali2 speak for all tubes or all tube amps. ZDS owners already know to allow at least 5 minutes unless they happen to enjoy the microphonic pinging of their power tubes that results from their thermal expansion during warm-up.

 

Alright, I'll bite. Tube amps need time for the tubes to warm up; they really don't sound their best the moment they're turned on. If you don't hear this, you might as well just buy an O2 and live in ignorant bliss.

What's next, are we going to debate that the sky appears blue, and get measurements as to which colour it actually is?

 

Can you really not hear the difference?? Actually, can you hear any difference between amps at all? Or is that another 'common belief' that needs to be examined...

 

This should not be a standalone thread. I admit it doesn't really fit in the all purpose advice thread, since it isn't exactly advice being sought. Maybe we need an "all purpose one-off questions" thread? Maybe this can be moved to the unsanctioned measurements thread and tacked to @doublea 's measurements once they arrive?

That said, @Cspirou nailed the technical explanation. Another helpful waypoint in your journey of discovery: old televisions. You are probably too young to remember televisions that ran on tubes, but they used to exist. Same kind of tubes. The picture usually started just as a horizontal line, and sucked until the tubes were warmed up. You could literally see the difference.

 

You're a sneaky one but I won't fall for it, my ninja like intellect protects me. When you categorize something as "blue" that's just a construct of your internal processes. There is no proof that your blue is my blue, what constitutes "blue" is entirely subjective. Your blue might be my red and I dare you to prove otherwise.

HaHa!

 

Exactly. This is such pointless HF crap.

 

I have an amp with tubes, an audio technica. It's extremely clear that there's a huge difference between when the amp has just been turned on and 5 minutes later. I tested it by listening to it immediately after turning it on and waiting 5 minutes before listening to the amp (just to eliminate the hypothesis that my ear adapt to the sound of the amp in the first five minutes which I had heard about but seemed extremely unlikely).

The difference is clear (it doesn't sound good at the beginning) and it makes complete sense since the filament is not warm yet. It's really one of the most uncontroversial truth about electronics.

 

The tube amplifiers I have heard have worse dynamics when cold. When I switch my EC on sound starts to appear like sound source would travel out of a cave. When you think about it, its stupidly logical. Electron emission rate speeds up with temperature.
There are other mechanisms that will interfere with tube warming up. PSUs usually stabilizes for some time for one.

 

Just to add, I encourage these questions and his measurements. A lot of people don't know about tubes and why you would want them.

That being said I did start a thread in the measurements section for exactly this sort of question which is totally ignored.

http://www.superbestaudiofriends.org/index.php?threads/measurement-requests.367/

 

Go to HF and ask Castle of Argh, he'll tell you.

 

O2s don't use tubes...

 

Hell, on my WA5 when I'm running my (mesh) rectifiers and the 300B power-tubes, they will ping loud enough as they expand and reach thermal equilibrium that you can not only hear it through the headphones via microphonics, but you can hear them through the backs of the headphones as raw, direct sound!

 

Haha, I didn't realize I was coming across in this way although it makes sense after re-reading my post. I was more curious about the specific effects that warming up has on a tube amp. Maybe some oscillatory patterns in the frequency response that level out, maybe thd goes down in certain frequency ranges as a function of time/temp, etc. Sorry for making it seem like an all-amps-sound-the-same post, I really don't feel that way at all.

Edit: updated my main post with an edit to try to clarify

 

It's an interesting question I suppose. I don't think there is any debate as to IF tubes need to warm up to sound their best I think more the question is what is it that is happening as far as their output as they warm up. IE, does distortion decrease, frequence response level out, etc. I'm not sure how the information would be useful but I think that is something that I have not seen someone measure.

 

What I'd like to know is the difference between a tube being fully warmed up as per manufacturer's specs or recommendations vs. opinions on the "true" ideal operating state of the tube.

For example Schiit saying after 30mins the tubes will be fully operational (don't quote me on this I don't remember the exact time Jason recommended) as opposed to somebody telling you "No, for the BEST experience you need to have the amp on for at least 4 hours."

This isn't so much a dig at those audiophiles as it is a query on the justification behind it, though I guess it comes back to the 'audiophile knows more about electronics than the engineer designing said electronics' thing.

 

<LOUD PINGING NOISES>

 

I'm getting PTSD from the original Vali 1 ringing pre-fix.
(Just kidding, it wasn't THAT bad)