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How Long to Burn-In Western Electric 300Bs?

I have a new pair of reissue Western Electric 300Bs that I am running in my Morrow Audio SET amps. I read some comments in a Stereophile column published a number of years ago in which the reviewer discussed a very protracted burn-in time for the tubes. The reviewer had experienced a dramatic change in the sound of his WE 300Bs after a burn-in period of several hundred hours. He later ran into the principal at Western Electric (Charles Whitener) at a trade show and inquired about the manufacturer's recommendations with respect to burn-in of the tubes. In a follow-up column, the reviewer relayed Western Electric's suggestion that the tubes require a minimum of 500 hours of burn-in.

The Stereophile follow-up column goes on to say that the Western Electric 300Bs require a much longer burn-in period than most tubes because WE chooses not to use calcium oxide in their filament coating. WE apparently believes that calcium oxide shortens the filament life. The downside of this approach is that it apparently takes a LONG time for the filament to burn in without the calcium oxide acting to accelerate the activation of the barium in the filament coating.

For those of you running Western Electric 300Bs in single-ended amps, I would be interested in your experience with respect to burn-in. Were there truly significant changes in the sound of the WE tubes hundreds of hours into the burn-in process?

Frankly, I felt that the WE tubes sounded excellent right out of the box, and I can't imagine there will be significant improvements. Nonetheless, I'm curious about others' experience.
cincy_bob
jeffreyds
115 posts
 
I have a pair of WE 300Bs with ~ 400 hours. For the first hour or so the sound was compressed and congested. After the first hour, the sound opened up. Beyond that, I haven't noticed much change in sound quality. The strange blue glow at the top of the tube becomes far less pronounced after a couple of hundred hours. Other than that, no changes to my ears.
philefreak
423 posts
 
IMHO, about 250 hrs is what you can hear. 500 hrs may be the true time for 100% break-in but, as far as what you can detect,the first 30 hrs will be the most noticable from then on it gets less noticable as the time rolls on. Enjoy your WEs. They are the best 300B tube still by a long shot.
pawlowski6132
592 posts
 
Herman; I'm no chemist so, the how's and why's regarding "calcium oxide shortening filament life" and "...activation of...barium...filament coating." Mean nothing to me. Heck he could be making those words up and I wouldn't know it.

My point is, through two new pairs, I've never heard a noticeable difference after this so-called burn in. Let your ears tell the truth.

While I'm willing to give the benefit of the doubt to the scientists that in theory, these things are true. I don't think it has a practical impact and can be heard through all the real-world daily fluctuations in sound quality happening on a daily basis (electricity quality, quality of the recording, tube quality in other components, needle wear, etc.)

As an analog, that's like saying Google's stock will go up if everyone in the company wrote smaller. In theory, they would use less ink, buy less pens, save on office supplies, expenses would go down, income would go up, market would recognize this increase in productivity and want to own the stock, increasing demand and increasing stock price.

In reality though there's too many other things going on overshadowing the small immaterial impact or, in other words - baloney.
cincy_bob OP
270 posts
 
Thanks for your input, guys.

Joe, in the end, what I think you are saying is that you have not experienced noticeable changes in the sound of the WE tubes in your system. Fair enough. There could be many reasons for that, including the nature of the specific components comprising your system and the type of music you enjoy.

Personally, I am hoping that there is some evolution in the sound of the tubes in my system, as the treble brightness I am currently experiencing at roughly the 40-hour mark is not pleasant when listening to classical music where strings predominate. On the other hand, the sound of the new tubes is already heavenly with vocals and with most jazz.

Time will tell, I suppose...
pawlowski6132
592 posts
 
Hi Bob; don't underestimate the impact of rectifier, input and driver tubes. Honestly, those tubes can affect final sound just as much if not MORE than power tubes.
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