Me too, I connect double REL T/7i to the ground of each M1200. Never tried floating black wire…
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I think Rel recommends floating ground for balanced amps. I am almost certain this recommendation applies to class D amps too.
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Correct
The REL instructions say to float the ground BUT if there is a hum issue find a chassis ground screw and use that connection point to attach the ground wire. https://www.youtube.com/watch?v=3F5WTOu60hE&t=78s
Attention to the design details of dual binding posts and chassis grounds making sub hookups easy is one of the things I appreciate about PSA amps. 
I’ve always used PS Audio’s ground screws to hook up my REL SHO/S3 subs on both the BHK and M1200 amplifiers without any issues.
REL manual says, with mono block amplifiers Class D balanced, to let the black wire floating or to connect it to ground.
From REL website:
Along with our friends at Peachtree Audio, the NAD folks also added an old-fashioned knurled chassis ground bolt which makes it even easier than we described to obtain true ground on this style of amp. We salute these customer-centric companies.
In the case of a chassis ground bolt like this, please DO connect the Black wire to this bolt”
I think the same rule is valid for PS Audio M1200s.
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Actually I have no hum at all and SQ is very pleasant. Just a little bit of hiss from tweeters only if I stay very close with ears to speakers.
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And I was thinking there were going to be more reviews of the M1200. I should know better, LOL
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I bet the hiss was there before, but please report back if you rollback. Cheers!!
Yes the hiss was present since BHK Preamp and M1200s first time entered my system, together the same day (and they brought the magic in my home!)
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Right there with you - as per my identical technical situation, but more importantly, THE MUSIC.
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Yes, the BHK Preamp to M1200 monoblocks is a wonderful and magical combination.
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I agree.
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In Germany the „biggest“ Hi-Fi Magazine elected the M1200 to be „unit of the year“ !!!
Congrats to Paul’s team.
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Happen to have a link or publication name?
I just completed 420 hours of Burn in on my new M1200’s
Was oddly cool placing them in standby before i headed to work this morning
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How do they sound?
They sound great!
Though embarrassed to say i dont appreciate a huge sound difference from compared to new.
Perhaps hard to appreciate as its a gradual process.
But love the amps…glad i chose to send the M700 back
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Glad you’re enjoying them! They do run pretty darn cool, even after being on for a long time. Just like the 700s, they hardly feel warm even at loud volumes.
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I have an update on the M1200’s. I have 2 speaker systems and 2 amp/preamp combinations that I use. Today I did something different and contrary to how the system has been connected before. I connected the Conrad Johnson PV10 preamp, via rca interconnect, to the Infinity Modulus crossover box and then to the M1200 amp, powering the sonist Audio Concerto 4 speakers. The Infinity sub was turned on, but with the sub volume down to zero. Also connected a Y split interconnect to the left and right outputs of the preamp so that the SVS subs could be used (instead of the Infinity sub). I chose to connect the Infinity crossover box into the system so that the high pass filter could be used on the Sonist speakers just as an experiment, as there was too much upper bass in the system. With the Infinity crossover in the system, everything below 140hz is cut off from the main speakers.
The subs are normally connected to the BHK Pre via rca, with the xlr going from the BHK to the M1200, with the speakers playing full-range and with the subs set to not play music above 40hz, but there is too much upper bass in the system that way.
All I can say is wow!!! The musicality is excellent. The system does not have too much upper bass with the active crossover in the system, and the midrange of the CJ preamp combined with the M1200 is truly wonderful. Female vocals are smooth and clean, violins sound like violins, saxophones sound like real saxophones. Even the audience clapping on Ben Webster Live in Copenhagen sounds realistic. The only downside is the front to back imaging isn’t there like with the BHK Pre to M1200 powering the Infinity Modulus. But if front to back imagining is the worst tradeoff, that’s something that can be lived with for now.
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Thanks for this great review!
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