How do you burn in new tubes

[maxg]

I am a bit confused by this thread. Are we discussing burn in or warm up?

To me Burn in describes the change of a tube (in this case) with age. In theory the tubes performance is an arc. Initially, as the tube "runs in" or "burns in" its sound improves. For a relatively long period of time it then stays effectively constant in performance and then towards the end of its life the performance degrades to the point the tube fails completely.

This is an effect I have not noticed to date with any of the tubes I have run (6550 WE Sovtek, KT88 (JJ), 6550C (Svetlana), EL34 (EH). That is not to say it did not happen - it may have done - but to me, at the time, the tube just played as a fairly constant level of quality until the day it failed and was replaced.

On the other hand if we are talking about warm up for a tube this is something I have noticed, and even measured!!

To me - warm up is the time it takes the tubes to stabalize once the power has been switched on. This, as far as I can tell, is a real effect and something I have observed.

When Tsakiridis showed me how to bias the tubes with a meter he was very clear that I should allow the amp to warm up for a good 10 minutes before making adjustments. On power up - I started measuring immediately and noted that the mV values I was getting no each tube was miles away from what it should have been. As time progressed these changed, apparently almost linearly as the tubes warmed up. After about 5 minutes (I wasnt timing it) they seemed to start to settle around the values I had been told they should be. After 10 minutes they appeared to be rock solid.

After biasing I left the amps on for another half hour or so and then re-measured. The results were just about identical give or take a digit (120 mV on initial measurement - now, say 121 or 119 - probably at the limits of the accuracy of the meter anyway).

I have never dared to play music through the tubes immediately after powerup so in all honesty I cannot say that this stabilizing of the tubes has an audible component - but judging by what is going on in the electronic measurements I would be amazed if there were none.

Of course it does occur to me that my careful biasing may have drifted off from the orginal settings over the 2 months or so that have passed since I last biased.

Could be another cause of run-in....although that suggests the sound shouldbe getting worse - not better.

As a final note - I used to leave my amps on all the time. A fairly recent flame out (previous thread in this forum - with pictures) persuaded me that this was not a good idea from a safety point of view. Now I turn the amps on about half an hour before I start listening. Has there been a change in the quality of sound? Can't tell - too many other sundry changes in the system during that time, but as the sound is better now (to my ears) than it was previously it is certainly no night and day issue.

[maxg]

"My best guess on tube break in is that it is psychoacoustic and not physical. But frankly, most people hate that answer. "

Psychoacoustics seem to be interesting. They are oft quoted as the reason behind hearing a huge number of things in audio - from differences in CD players, a preference for vinyl, changes due to cabling etc. etc. - even for the preference for low power SET amps.

My question is this:

Assuming, for the sake of argument, that a huge amount of what we hear is psychoacoustic if it is repeatable and brings more enjoyment to the listening of music, does it really matter if there is no underlying physical cause?

Ultimately I do not take the term psychoacoustic as derogatory when used to describe my observations, or those of others. Music is not merely sound, or even a collection of sounds. Music is emotional impact. It stirs the soul, moves the mind (and body on ocasion). It is all about psychology. Purely psychological impacts, therefore, of a change brought about by a component swap (for example) are as real to the beholder as changes brought about by demonstrable physics, biology and chemistry.

Of course there is always the simple fact that science itself is a moving force. what cant be explained today can be tomorrow, and then contradicted the day after. I just read (on CNN I think) about a group of scientists that have just "transported" a couple of ions - ala Startrek. Apparently they have particles that are related even though separated by distance - when one changes the other one does - even when there is no direct connection between the 2. Spooky science - according to Einstein.

[Parrot]

A lot of psychoacoustics is focused on trying to find the underlying physical cause and figuring out how things are processed in the brain. Nobody gets anywhere if he just settles on "It's all in the mind." That's more of a pop psychology thing.

Concerning the Star Trek-like transporting: Imagine the insurance.

[NOSValves]

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On 6/15/2004 9:27:49 PM edwinr wrote:

Yes it makes more sense to switch on and off as you please, as I have always done. I have friends who leave their gear switched on all the time (or so they tell me - although none run 300B's). I had a thought about the debate about tube rolling. I think ultimate tube sound is more influenced by transformer limitations rather than the actual choice of tube or whether PP or SET (not that I have much SET experince). If transformer design and quality is top notch only then would the selected tubes be able to show their full potential. My amplifier is definitely low to middling in quality (Jolida 202b) and any tube rolling I may do would be more for fun than a serious attempt to improve sound quality.----------------

You have a very good understanding ! The transformer is the last thing to touch the music !

[Colin]

I think MaxG is on the right track, perhaps all we are talking about is drifting bias, it may NOT be possible, but we should all measure the bias settings first, during and then afterwards then we could talk about tube warm-up

BTW, I will let my tubes stay on all weekend, but during the week, I turn them off

[radiob]

Try hooking it to 220v, it will speed up the "break".

[mike stehr]

To the cathode/heaters or the plates?

220 on the heaters would be fun to watch.

Aren't tubes "burned-in" at the factory, then tested and sorted?

I kinda assume once the amplifier chassis circuit/tubes are all up to operating temp, your "broke-in", usually around a hour.

(Like Mark said.)

And the 100 hour break-in theory with some coupling capacitors. Can a guy aurally remember what characteristic

sound the coupling capacitors had in the first hour, when it is the 100th hour on the circuit?

It would seem to me that the capacitors should be broken in within that time frame when the circuit and chassis come up to operating temperature, who knows.....

IMO, ear break-in plays in a bit. The local audio friend and I seem to agree our ears can get used to things rather easy.

I dunno, just make sure the tubes always have good emissions. When they die they die.

You can leave them on all the time and have the safety risk, and the tubes are still burning up life.

Or you can stress them out on thermal cycles, killing emissions that way, it's a balancing act.

I hate having to turn on my triode amp and only listen to it for a couple hours, the damn thing takes a hour to warm up. I like running it all day when I can.

That's why I have junk console amps, so I can beat the piss outa them for short term listening sessions.