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Output tubes burn-in

I just replaced the 6550 output tubes in my Audio Research Dual 75 power amplifier. The new matched pairs (and regulator tube) came from Audio Research.
The last time I did this, I burned the tubes for 20 hours before listening since I've read that it takes that long for the music to sound good. This time, I'd rather listen right away rather than waste 20 hours wating for the "magic" to happen (it really does), but I wondered if a straight 20 hour burn-in is the way to go. Or, if you kept listening until you hit 20 hours, would the result would be the same (music sounding better)? In other words, is there any advantage in strictly waiting for a continous 20 hour burn-in period? Any comments based on experience?
kisawyer
whart's avatar
whart
3,016 posts
 
Pretty cool that you have and still use a Dual 75. I have a Dual 75a that i bought from a dealer in around 1974 and have maintained it over the years, had it recapped, etc. several years ago, and just ordered a new set of output tubes from ARC. I don't really use the amp anymore, but have kept it for sentimental value. Out of curiosity, what did you use to plug into those quarter inch jacks to bias the tubes? I have a meter, so that's no big deal, but I'm not sure how those jacks are wired.
And, fwiw, different tube equipment would seem to react differently to burn in, in terms of sound. I just retubed my SET Lamm amps, I really could detect no shortcoming in hearing the new tubes, in fact, the amp probably sounded better. In burning in my new phono stage recently, (an Allnic) it took forever, and the sound changed dramatically over time.
kisawyer OP
24 posts
 
Whart, Years ago, a friend gave me a Weston milliamperes meter device. Connected to it is a "banana" plug that fits into the balance and bias ports on the Dual 75. I follow the biasing insturctions outlined in the ARC Dual 75 insturction manual. It works great.

I'm "Old School" and have owned this amp since it first came out. I've heard that ARC built only 130 of them.
kisawyer OP
24 posts
 
Tpreaves, That's the problem with listening...once you hear/hit that "magic" sound, you always want it to be there. Isn't that what we audiophiles strive for in our listening?
arh
366 posts
 
Listen while you burn in. It won't make any difference. In most cases the results of burn in is small except for speakers. Enjoy
Alan
whart's avatar
whart
3,016 posts
 
Thanks, Kisawyer. Yep, even back in the day, you didn't see those much.
I suspect the really early ARC stuff, including the Pelpoe(?) Industries equipment that WZJ first made, is extremely collectible these days. I owned alot of ARC stuff over the years, had the companion SP 3-a-1 preamp, then eventually went to the SP-10mkii preamp, which I used for a long, long time. Also a succession of amps, including D- 70mk ii, and Classic 60, all of which I used on my Quads. I kept the Dual 75 a for some reason, and used to use it in my home theatre system, which was at one point all tube amps. Kinda got warm watching a movie. :)
The company still makes really good products, and provides amazing support, with that mid-western sincerity that seems so out of place in NY- but I find kind of endearing.
I still have a bunch of older equipment that I eventually need to restore, including a pair of Quad II amps, a pair of vintage Decca ribbons and of course, my original Quad ESLs. Just a question of time, money and priorities.
Thanks for the info, and continue to enjoy your amp. I kinda liked the build style of the Dual 75, with that gap in the cage.
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