What’s wrong with just playing them when you want to listen, knowing the SQ gets better every time you do so? I assume that you keep the M1200 longer than 100 h of listening pleasure. As you say, they do not sound horrible, even right out of the box.
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I have always listened to my gear during the burn in
process…the shortest about 50 hours…more typically
300-400 hours the longest was 1000 hours but still
listened during the process…though frustrating as it
was…still listened…
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Agree with @davida I always listen while the rig is burning in, I like the changes and the development of the sound over time and the moments where it comes together, wouldn’t not want to be there for that. Would be like missing the kids first steps!
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Thanks for the response sand. I think your 400 hour mark sounds quite reasonable. Sounds like folks start to hear a bit of a break through at 250, but need another maybe 200 to get through all of it.
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Couldn’t have said it better myself aiki.
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Absolutely nothing is wrong about that. Some want to skip that step so we’ve offered a practical and proven way to accomplish that.
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I was curious to when most have noticed the amps reached there optimal performance. 400 hours or more sounds sensible.
I don’t have any reason to think M700s are identical in this regard, but it seems likely more improvements are to come in mine beyond the 300 hour mark I’m at now, especially since the vast majority of those hours were spent at very low levels while I was doing other things.
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The M1200s weigh 2x the M700s. Obviously, larger power section, which is probably where most of the burn-in / break-in takes place. My M700s took about 200 hours, not more. The interconnects and power cables took longer!
400 h average listening time 1/2 to 1 h a day. That would be 1 to 2 years. Time to roll the tubes at optimum, nice perspective. EAT in Czech Republic make Great tubes (and turntables).
1/2 hour to an 1 hour a day of listening is like eating two potato chips out of a bag, not possible. Lol. My stereo is on 4 to 10 hours a day sometimes more rarely less! 
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Ok I’ll let you go with 2 potato chips but no more before dinner 
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That’s quality listening though, the stereo is also connected the entertainment system. I forgot that. Off course that burns the equipment in too.
I received my M1200s in May, 2020… They’ve been driving the very effficient Serenity Super-7s until about a week ago when I reinstalled my Vienna Acoustics Mahlers… The M1200s drive the 89dB-inefficient Mahlers VERY well… Removing the Super-7s simplified my system; the next step was to add another multichannel Emotiva XPA Gen3(1) to get the of 200-Watt mono channels to five to biamp the Mahlers and single-amp the CC speaker…BUT…my thoughtful wife observed that while simplication and saving a couple-thousand dollars are admirable goals, continuing to love the sounds of my system is a more-important goal… So the M1200s are still in the system, and the system is still making beautiful music.
The Emotiva rear.
FWIW, the Mahlers’ MR/treble crossover included a 310uF(!) bank of film caps acting as hi-pass (at around 70HZ if I recall correctly) filters for the identical-looking upper-bass and the upper-bass/MR drivers… Removing those caps improved the transparency of the speakers significantly, AND the two upper-bass drivers have never rattled(2). 
I considered rewiring the bass drivers (dual 9s on the outsides of each box) to be driven directly by the poweramp channels and driving the poweramps’ bass channels with an active Dalhquist DQLP-1 filter (which I’ve had for decades), but the quality of the bass driven passively as they are is SO good I decided against that.
.
.
(1)…to the 11-channel XPA-11 Gen3 that’s driving the center and all-10 surround and ceiling speakers
(2) But then again, I’m not an eardrum-smashing dideebopper!
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This is off topic but I was wondering what speaker cables you are using for your surround speakers? Thanks
Beautiful wood cabinets. Are you using subs in your theatre operation?
Something very much like this.
https://www.homedepot.com/p/Southwire-500-ft-16-4-Grey-Stranded-CU-In-Wall-CMR-CL3R-Speaker-Wire-56911645/202316386
16g.-times-4 when paralleled becomes 13g.-times-2. I also used this stuff for the bass-only cable when I rewired the Mahlers years ago. In that case, 16g.-times-4 becomes 10g.-times-one, and I then used two cables, one per pole.
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Thank you, but I wish they were darker (I bought them used)… IIRC, Mr. Vienna Acoustics called that veneer ‘flame maple’.
SWs are a pair of Rythmik F18s…
Used only in multichannel mode, they’re driven by the pre/pro’s dual LFE outputs, which, of course, are mono but separately adjustable… They’re used only as SUBwoofers and not woofers, with the low-pass filters set to 25Hz… They are quite effective for low-frequency effects and the occasional multichannel SACD that drives the ‘.1’ channel… The Mahlers have quite-good-sounding bass extended well into the 20s, so the SWs are not needed for music.
It’s time for a little update. I have been doing a lot of listening and comparisons to the other amplifiers I have in house…namely the VTV purifi monoblocks with tube input buffer, Bel Canto Evo and the Benchmark AHB2.
To be honest, I was struggling with the M1200’s. Following my initial, very good impressions, the amps just didn’t seem to open up the way they should. I thought more burn in may be needed, so I crushed them for four more days both with speakers connected and without them connected and my preamp feeding the M1200s a maximum signal. This seemed to bring up the lower mids and upper bass a bit, filling in what I had initially perceived as a hole (more like a divit), in that frequency range, but I was still lacking the holographic imaging that I was consistently getting from the VTV amps. I also noticed that the soundstage was huge, almost too large, with the M1200’s, and the ambient hall sounds much more prominent than on the other amps. A prominence that seemed out of place in the balance with musicians and vocalists at center stage.
This frustrating experience made me reflect back on my “tube-fest” days and I remembered one instance where a particularly well regarded amp had similar sound anomalies. Back then, I thought I was going insane for not liking it, that is, until the designer told me that one of the input stage tubes may have gone microphonic. Hmmm…could this be the issue with the M1200’s? I happened to have a pair of Herbie’s Ultrasonic dampers on hand, so I cracked open the amp cases to see if the Herbie’s might settle these tubes down. By the way, with cases wide open, I got the chance to appreciate just how well built these are and observe the attention to detail - like the vibration damping material used on the caps and transformers… nicely done PS Audio. While inside, I also noticed that one of the tubes was a little loose - not fully seated in its socket. It stands to reason, to me at least, that the horizontal mounting of a tube may exacerbate vibration problems - think lever and fulcrum, angle of momentum, you know, “science!”… So I applied the Herbies, buttoned them up and had another listening session —and… the sound was utterly transformed! Without a doubt, the tubes were the culprit. The anomalies I had identified before were gone. The soundstage was still larger than the other amps, but it was now glorious, not ridiculous. Imaging within the stage was now approaching Star Trek “holodeck” quality with excellent inner detail. I was overjoyed! Finally, I was hearing what the M1200’s are all about…that great initial impression more fully realized. I tell you what, I was really excited and decided to take this tubes/vibration experiment as far as it could go. I broke out the 'ole Townsend Seismic Sinks and the Black Diamond cones and added them to the mix. Once again, a smaller, but nevertheless, notable improvement. Herbies dampers are like the sledge hammer and the other stuff are more like scalpels.
I finished my experiments by ordering up a matched pair of the Genelex Golden Lion AU7’s. These are one of my favorite affordable AU7 tubes and it just so happens that it has a more squat and robust build than the PSVane. I’m still ruminating on the lever/fulcrum/momentum thing and I don’t know if it really applies here, or if a better pair of the PSVanes would eliminate the distinctions, but holy cow!.. these Ruskie tubes sure do sound fantastic. Your mileage may vary. I’m just happy that I can now hear the M1200’s in their best light (for me).
I don’t want to entirely give away my upcoming review, so I won’t get into all the subtleties and details, but I am willing to stick my neck out and state that I can’t find any weaknesses with the M1200’s and that in many respects, it is easily the best amplifier I’ve heard in my listening room. They are staying in my system for the long term and I guess that now makes me an official PS Audio guy.
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Great intro to your anticipated full-on review.
Thanks Stuart