Biasing Ref 110

bonzo75

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Feb 26, 2014
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Hi, my Ref 110 is with KT120s, does anyone know after roughly how many hours of play you need to bias these?
 

mep

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Apr 20, 2010
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If it has been awhile since you last checked your bias, just hook up your meter and check the bias readings. If they need to be adjusted, just adjust them.
 

DonH50

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Jun 22, 2010
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+1.

The (maybe just "my") ancient quickie rule was 1-10-100 -- check at 1 hour, 10 hours, and 100 hours. 1 hour to catch any initial burn-in drift, 10 hours after they have settled a bit, and at 100 hours they should be in "long-term" mode. I would check every few months after that, which might be 100 - 300 hours -- whenever I thought to do it. Some tubes would drift very gradually then change rapidly at EOL (end of life); others seemed to drift slowly at first then a little faster as they aged until they died.

Just a rough guideline; some will check after every record or CD, at least until they tire of it, and some will check when they replace them and never again. The 1-10-100 rule worked pretty well for me over the years.
 

bonzo75

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Thanks guys
 

microstrip

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May 30, 2010
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+1.

The (maybe just "my") ancient quickie rule was 1-10-100 -- check at 1 hour, 10 hours, and 100 hours. 1 hour to catch any initial burn-in drift, 10 hours after they have settled a bit, and at 100 hours they should be in "long-term" mode.(...)

Don,

Although I broadly agree with the timing my wording would be different for ARC modern amplifiers - 1 hour for temperature and amplifier stabilization, 10 hours for leaky tubes and 50-100 hours for burn-in. I have measured several sets of 6550C and KT120 during burn-in with my burn-in and matching jig and found sometimes they take about 30 hours before fully stabilizing bias.

If people get tubes already burn-in from ARC they can follow ARC instructions.
 

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