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12AU7 burn in

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blueflog

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12AU7 burn in
« on: 31 Mar 2013, 05:25 pm »
Hi,
I plan on installing 4 NOS 12AU7 tubes soon. On average, how many hours does take to burn in new tubes?
Thanks!
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JakeJ

Re: 12AU7 burn in
« Reply #1 on: 9 Apr 2013, 07:34 pm »
20-100 hours.  A lot depends on your systems resolution.

Just my .02 based on experience.
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K Shep

Re: 12AU7 burn in
« Reply #2 on: 9 Apr 2013, 10:35 pm »
Quote from: JakeJ on  9 Apr 2013, 07:34 pm
20-100 hours.  A lot depends on your systems resolution.

Just my .02 based on experience.

Is it your experience that in those first 20-100 hours as the tubes "burn-in" there is an audible change?
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FullRangeMan

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Re: 12AU7 burn in
« Reply #3 on: 9 Apr 2013, 10:43 pm »
Usually if the tubes have to show a manufacture problem, it should appear in this initial 100 or 200 hours period.
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medium jim

Re: 12AU7 burn in
« Reply #4 on: 9 Apr 2013, 10:43 pm »
Quote from: K Shep on  9 Apr 2013, 10:35 pm
Is it your experience that in those first 20-100 hours as the tubes "burn-in" there is an audible change?

It is mine that they or any tube will audibly change during the burn in. As the gases fully form, the edge goes away.

Jim
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TJHUB

Re: 12AU7 burn in
« Reply #5 on: 9 Apr 2013, 11:37 pm »
I just broke in several pairs of tubes.  All of them seemed to take 150 hours or so to fully become clean and clear sounding.  They changed the most over the first 50 hours, but they seemed to gain in clarity over the next 100 hours.  One pair of tubes I didn't like after 50 hours was more acceptable after 150+ hours.  Of course they still got pulled. 
« Last Edit: 10 Apr 2013, 03:23 am by TJHUB »
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JakeJ

Re: 12AU7 burn in
« Reply #6 on: 10 Apr 2013, 07:35 am »
Quote from: K Shep on  9 Apr 2013, 10:35 pm
Is it your experience that in those first 20-100 hours as the tubes "burn-in" there is an audible change?

Yes.  Plus I agree with Fullrangeman, and Medium Jim and TJHUB apparently have had the same experience.
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Ericus Rex

Re: 12AU7 burn in
« Reply #7 on: 10 Apr 2013, 11:53 am »
For me, the biggest and most noticeable change has occured in the first 20-30 hours.  Then the change is more subtle after that.

If you want to know what's happening during this break in there's a section in Bruce Rozenblit's new book that explains the process, probably more deeply than you care to know.
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K Shep

Re: 12AU7 burn in
« Reply #8 on: 10 Apr 2013, 07:01 pm »
Quote from: JakeJ on 10 Apr 2013, 07:35 am
Yes.  Plus I agree with Fullrangeman, and Medium Jim and TJHUB apparently have had the same experience.

Actually Fullrangeman said problems show in the 100 to 200 hours. 
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JakeJ

Re: 12AU7 burn in
« Reply #9 on: 10 Apr 2013, 07:23 pm »
Yup, that's what I was agreeing to.  My post was confusing, sorry about that
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FullRangeMan

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Re: 12AU7 burn in
« Reply #10 on: 10 Apr 2013, 08:14 pm »
Quote from: K Shep on 10 Apr 2013, 07:01 pm
Actually Fullrangeman said problems show in the 100 to 200 hours.
I mean say under 100 hours or so. Of course it dont grant the tube will came to a benign death.
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