? about tube burn in time

[Mwin35]

Hello i'am new too tube gear and just bought my first tube preamp.
How long does it take to burn in new tubes?
Thanks for the info

[Peter Wieck]

François Yves Le Gal wrote:
> On Tue, 12 Sep 2006 00:22:22 -0500, "Mwin35" > wrote:
>
> >How long does it take to burn in new tubes?
>
> Despite what you can hear and read everywhere, there is no "burn-in" period
> for tubes. They are usually fully tested at max specs - a form of "burn-in"
> allowing to separate the wheat from the chaff - by the manufacturer and/or
> the distributor and won't incur changes in use. Of course they will age
> while in use, but you can expect thousands or even tens of thousands of
> hours of service in a well designed and well built preamp.

True as far as it goes. Here comes the "however":

Some tubes are just not very good. Depending on the ethics of the
manufacturer, the screening processes of the instrument/equipment maker
and/or the simple luck of the draw, what you get inside your new
pre-amp may just be not very good tubes. Or, some of the latter-day
Chinese companies simply test the tube to see if it lights, then out to
the loading dock.

As François states accurately, no amount of burn-in will cure these
sorts of defects, although you might be told just that. As an aside, it
has been my experience that catastrophic failure in a "new" tube
typically happens within the first 48 hours of use and/or the first
sustained use. But not every manufacturer is the present incarnation of
Western Electric, most use a form statistical batch testing with many
tubes not tested at all. THOSE will require a burn-in, but that will be
a few hours.

I commonly advocate that power output tubes (NOT what is in your
pre-amp) should have their bias checked (if applicable) for the first
20-30 hours of use, just in case. But, François is right again when he
suggests that tube life will be many thousands of hours in a
well-designed instrument.

Cutting to the chase, if there is something about the sound of the
pre-amp that you do not like, and all things are otherwise equal, it
may be the tubes. If that annoyance lasts more than a few hours of
use... 10 at most, those tubes are BURNT IN, or as burnt in as they
ever will get. It is a pre-amp, typically not a stressful environment
for a tube. After that 10 hours or so (at most), they won't get any
better.

Peter Wieck
Wyncote, PA

[Ian Iveson]

Mwin35 asked:

> Hello i'am new too tube gear and just bought my first tube preamp.
> How long does it take to burn in new tubes?
> Thanks for the info

What does "burn in" mean, do ppl think?

To me, "burn in" takes a component or an assembly to the edge of, or
beyond, its normal operating limits for a relatively short time. A
"soak" is carried out within normal conditions for a relatively long
time.

Anyway, it will cut a long story short to assume that you are
concerned about sound quality rather than reliability.

Let's assume your preamp is so optimally designed that it only sounds
its best when the valves' characteristics are exactly as specified.
Also assume that the valves are so perfectly manufactured that they
all match those characteristics for most of their lives, and that they
have already been burned in by your supplier, but not soaked.

Broadly speaking, a valve's characteristics will change most rapidly
very early in its life. It will then stabilise to a gentle pace of
degradation.

Consequently, your ideal preamp with ideal valves will improve for a
shortish while, sound its best for quite a long time, and then slowly
decline. In normal domestic use, perhaps a week or two and a couple of
years. Depends on the valves and their operating points.

In reality you will be lucky to hear any difference, for better or
worse.

Why do you want to know? You can't do anything about it anyway. If you
can't hear it getting better, assume it won't. If you can hear it
getting better, it could just as well be your perception is changing,
and in either case it will soon settle.

Unless you have control over the circuit, or you want to get into
swapping, or "tube rolling" as they say (why?), don't fret.

cheers, Ian

[Tom Schlangen]

Hi,

> How long does it take to burn in new tubes?

It depends. Usually, new small signal tubes have
no burn in time to speak of.

For larger ones, it can take its time. The worst ones
I ever encountered were some Zaerix 807 and Siemens
QE06/50, both actually produced in the former USSR,
but from different plants.

They needed >48 hours of simmering at about 80% Pd until
plate current stopped to wander around. No chance to
match them before. (At least not what I understand
with the term "matching"). After that, they stayed rock
stable during about 300 hrs of operation by now.

Tom

--
When in doubt, use brute force.
- Ken Thompson

[Phil Allison]

"Mwin35
>
> Hello i'am new too tube gear and just bought my first tube preamp.
> How long does it take to burn in new tubes?
>


** It is YOUR gullible, audiophool brain does the " burning in " - not
the damn tubes.

Go back to the whatever audiofreak's lunatic asylum you escaped from -
TROLL.




........ Phil