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?
As I have always done, I listen and enjoy the burn in process. Part of the key to enjoying high end systems is to witness first hand the changes that occur as things settle in and form the new sonic envelope and space. The same goes for speakers, cartridges and cables. Hey, you have a great system, play it, enjoy it and listen.
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
Just listen to the music and stop worrying about it.
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.
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.
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?
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.
Whart, The ARC gear I have has been with me since about the early 70s. I have the D 75 and D51 amplifiers and the SP-1C preamplifier which was WZJ's first preamp, I believe. The original face plate it came with said "Electronic Industries." I later got the one I now have which says Audio Research (its a rack mount plate). I'd love to hear some of their new equipment, but now-a-days they are way out of my league.
Did you ever listen to the D75 with the speaker wires reversed from the normal connection? Their literature says the D75 (and the D51) was "an INVERTING amplifier - the output signal is 180 degrees out of phase with the input signal." From that statement I've always listened with the speaker wires reversed (at the amplifier) from the normal amp to speaker connection. The resulting sound is simply seductive. You hear more detail, delicacy, and atmosphere than you would ever hear with a standard connection. I asked ARC about this and they confirmed it saying some people preferred to listen to the amp that way. I wonder how many owners of that amp never really realized this and the potential it produced. I listen to it this way all the time.
Kisawyer: Man, you are really one of the few! They should reserve a place at the museum for your system. The D-51 was a sweet little amp. I vaguely remember the SP-1, honestly can't say if I ever heard it. You are right, of course, that the products were branded Electronic Industries early on- somehow, I pulled 'Pelpoe' out of my, ahem, ear? I couldn't remember the connection with that name- I did a quick search and they bought him out early on, but I think that was really before ARC. You also know that some of his first amps were basically heavily modded Dynaco St 70's, right?
I doubt i ever inverted the leads- I used the amp with my old Quad ESLs (which weren't quite as old in 1974), and I think i just used the 16 ohm tap. I also vaguely remember something about a floating ground, but I may be misremembering that. It has been a while. I still have all the packing and literature that came with mine (I need to hunt for the screwdriver) so I will dig down when I retube. I need to replace the barrier terminals- they have had their barriers broken off since the 1970's when the amp was in active use- i just never got around to replacing them, and ordered new terminal strips from ARC which arrived yesterday, along with a new set of power tubes.
The company, as you know, went through a variety of 'sounds' over the years. They even introduced a failed solid state product at one point- i think they called it the 'analog module'- they were sealed modules on the circuit board that were 'like' tubes- I don't think that went very far. And of course, they had their 'white period' when the tube stuff sounded drier and less euphonic. I've heard the current Ref stuff and it sounded great on big dynamic speakers.

You should let the company know if they don't already that you are still running these pieces. It would be an interesting PR exercise for them to show an owner who has had their equipment for 40 years and still enjoys it.
That's very cool.
Whart, ARC does have a museum for their products. Anyone in the Minnesota area are told to stop in. I had mentioned to them on several occasions that I owned the SP-1C and they asked if I would send them pictures of it for the museum, which I did. It sounded like they were still working on what will be on display there, so no literature or photos of the place are available yet.
Here is another story you might enjoy. WZJ personally delivered the preamp to me and an audio friend in Milwaukee back in the 70s. We all three listened to it through my friends Bose speakers. We treated Bill to a prime rib dinner at my friends home to thank him for making the trip down and bringing the equipment. Those days are long gone!
Also, I remember going to a high-end audio store Chicago back then to hear ARC's Dual 100 amplifier. It was a monster, having two huge chassises and a large number of tubes.
Heard the story about ARC’s evolution experiment in sound over the years.
I've owned a Marantz 10B, (which I stupidly sold), had a pair of KLH Model Nines (which I stupidly sold), run by a Marantz Model 15. That never worked well, and made me a devoted tube man. Later, I owned the A&D mercury uni-pivot tone arm (which I....), and finally a pair of Infinity Servo-Static One speakers. The Infinitys’ were great, but they were made out of "bubble gum and tape." Sounded terrific when they worked. The company’s service at the time was horrible. Arnold Nudell had a great product, but very unreliable. I still have two pairs of them in non-working order stored away.
Try the amplifier/speaker lead reversal if you get your ARC amp running. I'd be curious to hear what you think.
You were really there. I remember the KLH 9- I grew up in Pittsburgh and the store which had the highest end stuff was Opus One. Tasso Spanos, the owner, was a KLH 9 devotee. (I think this was in the days of the Janzen tweeters) The 10B was, for me, the fish that got away- a friend promised to get for me, - one that had been on display at a showroom in NYC for years since new -but it never happened. I only met WZJ once, briefly, when I worked as a drop out in an audio store. (I was probably about 19 or 20 at the time). And i certainly remember the Servo-Statik but never heard one.
I was always pretty cautious about using any amp with the Quads, but once i get the Dual 75a retubed, I will probably run it through a set of dynamic speakers first and will try the phase thing. Best,
Bill Hart
Whart, Hope you don't mind another audio story. Since you mentioned Opus One, here is another.
My friend owned/co-owned the audio store "Opus Two" in Memphis, TN. When I visited him back in the early 70s, they had rack mounted Marantz Model Nines (two), 10B and 7C preamp all arranged in a very attractive wood paneled wall. It was stunning to see.
He also had the KLH Nines.
I was helping out one day in the store and in walked Isaac Hayes. He was very shy and was interested in the new "audio chair" that had just become available. It was the chair which had speakers enclosed within a “cocoon” type of arrangement. Isaac asked the price of the chair was and was told it sold for $700. He reached into his pocket, pulled out a wad of money, rolled off seven one hundred dollar bills, and then asked, "Does it come in red?"
Love it. I think i remember that chair. Issac Hayes was the man. Great story, you could do a blog of audio days gone-by. It would be fun to read.
Keep 'em coming.
We visited Memphis recently- the bbq was phenomenal, we went out to the 4Way for some soul food, and of course, we did Graceland and the Sun Studios tour. I thought Beale St. was disappointing- at best hard rock blues, no country or delta blues or any other kind of blues that we could find. Some of the storefronts were great, but the city had a very dangerous vibe (I lived in NYC during the crack-crazed 80's, and know what 'edgy' is about). Too bad, cause it has the potential to be a little jewel of a city- nice architecture, the locals were cool, and man, that bbq! You could smell it when you woke up in the morning in town.
Whart, Memphis. My old audio buddy from Milwaukee lives outside of Memphis. When I visited him and his wife about five years ago, we went to Memphis. You are right about your impression of the place. I didn’t care for the city.

I was floored, however, by the beautiful architecture of the homes there (especially East Memphis), and could not believe how much one got for the money in a house...at that time. The homes were beautiful.

My friend was a MacIntosh guy. He had a Mac C-22 preamplifier and 2105 power amplifier. I use to get jealous that his Mac would drive his KLH Nines while my Marantz 15 would clip and cause fuses to blow in my Nines. He also had a Marantz 10B.

There was a rivalry between MacIntosh and Marantz fans during those heyday years at the beginning of high-end audio. You could see it in the advertising literature of the day. Ads in Audio, Hi Fidelity and Stereo Review magazines showed Mac equipment in the home of some rich guy with a black Herman Miller lounge chair and ottoman. One got the sense of “being rich and owning MacIntosh.” Even the gothic font in their name denoted class!

The Marantz crowd beamed with pride at the beautiful brushed gold look of the equipment, and the quality finish. The 10B was simply “Da bomb” as the kids say now-a-days. And, the Marantz crowd believed that their gear sounded better than MacIntosh. I still have some of those old magazine ads in a scrap book somewhere.

Besides WZJ (who I consider the Steve Jobs of audio), the other guy I’ve been impressed with is Dr. Roger West of Soundlabs. I met him at a CES show in Chicago sometime in the 90s. Listened to his speaker and was quite impressed. He is a very nice person, having taken the time to talk. He apparently worked at Electronics Industries and knew WZJ.
Didn't know about the West-Johnson connection. Remember Dayton-Wright?
Of course i remember the old McIntosh stuff- even owned a few pieces along the way.
why don't you email me at bill@flyingreptilemediagroup.com
We can connect offline.