Do old valves need running in?

I had a pair of Shuguang 6SL7G Treasure series valves in my Cary's until one of them started emitting a very high pitched squeal (not microphony). I pulled them out and put them in a drawer which was a shame as I thought they sounded very good indeed (better than RCA etc). Since that time I've been running a lovely pair of vintage Tung Sols bought from a member of this parish and have been very happy with their open airy sound, good bass but also a slight hardness in the mid. So yesterday for some reason I decided to try the Shuguangs and put them in - no squealing but also weak bass and a degree of confusion soundstage wise. Basically not how I remembered them. As they've been in a drawer for around 4 months my question is do they need running in again? Or is my memory fooling me?

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Originally Posted by farflungstar

Basically not how I remembered them. As they've been in a drawer for around 4 months my question is do they need running in again? Or is my memory fooling me?

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Beginings of Wisdom therin.

Self-Analyse.

Well the answer is yes. After a couple of days the Treasure 6sl7's came back on song. Wow. Some great listening - better depth, slightly sweeter highs - until today when the same tube began emitting the same high pitched whine. Bugger. So out they came and back in went the tung sols.

This has confirmed how great the Treasure 6sl7's are - but I don't wanna blow 290$ for one of them to go tits up again. Hmmmmm....

Very old valves can need "running in", more a case of hoping the gettering will absorb any gases released from the internal structure over time really, and not always successfully. We're talking valves over 25 years old here and usually more like 50 though.

Well the treasures aren't that old jez but they changed significantly over a couple of days - no not accusomisation. I'm a bit pissed as the whine didn't happen for the last week of play - until today! Bugger.

With nothing to lose Adrian put the offending valve in the freezer for a day, take it out until room temp, then repeat.

See if it still whines afterwards, if so use as an ornament :)

Really - freezer? ok will try that.