Marantz PM Ki Ruby vs Musical Fidelity M6si

Ruby owner here (integrated first, followed by SACD player): I’ve been extremely pleased with both pieces, but especially the amp, as I’ve shared in other posts here & on Hoffman’s board.

I did not audition the MF; I’m sure it’s a fine unit.

To summarize, I find the Marantz open, fast, non-fatiguing, with a very good phono section & headphone amp. A little while back I switched in an old iron lung power cord (and a new Amazon sourced hospital grade $15 power cord); I continue to shake my head as to just how good this thing sounds. Believe I’m in for the long-haul with this one, I can squander my $$ on other things now...

Looking at both Rubies together as a system, the convenience of a common remote to control the amp & silver disc spinner has grown on me and girlfriend; she’s comfortable using and enjoys listening to the system. (Think long-term, big picture here..) I can use the DAC in the SACD with a streamer. Food for thought, esp with the prices on the amp coming down.

Hope this helps, feel free to pm me with any questions.

@p3ga thanks for the detailed review. Funny enough, I have a very similar setup. I use the node 2i for streaming but is hooked to a marantz sa8005. I bypass the node dac and what a pleasant difference it has made. Everything is so much more musical and non fatiguing.
I’m fairly clear about the ruby but I’m also getting a decent deal on the PM 10 (still considerably more expensive than the ruby).
Have you had the chance to try the pm 10 by any chance? Is it worth the extra dough or should I stick with Ken’s last work of art with marantz ?

I did not try the PM-10; at the time I was looking, I could not justify it at full tariff, so it never entered the thought process. I'm confident that it offers some advantages over the Ruby integrated, especially at the price delta between the two. I might, however, need to spend a retirement-postponing amount on speakers & peripherals to appreciate the difference between the two.

I hope you have the opportunity to try both and would be interested in your findings. 

@p3ga  guess what.. I got the Pm ki ruby. Arrived yesterday and I have spent a few hours with it.

initial impressions, nothing ( and I mean literally nothing) sounds harsh at even very high volumes. Treble is definitely rolled off but there’s still plenty of detail. Mid range and bass are excellent. Vocals are gorgeous and bass is tight and fast. With the musical fidelity 5si, often times I couldn’t go past a certain point with a lot of tracks before it got bright and fatiguing. Don’t take me wrong, MF is a fantastic amplifier, I was considering going for his bigger brother 6si. Very lively and energetic sound. Very musical too. Was a bit too revealing for my dalis esp when playing tracks with a wide dynamic range.

Anyway, the negative seems to be the flip side of the pro. Everything sounds a bit darker and sometimes unexciting.  It’s too early to come to any conclusion but these are just my initial impressions.  Does this make sense?

what changes do you think I should expect as it burns in?  
Thanks again for helping me pick this amazing and unfortunately, underrated amp. I’m elated even with the way it is right now.

I am done looking for perfect measurements and clinical sound. I just want engaging music and the PM ruby shines on that front. Great work by KI!

Well congratulations on the new addition to the family!

There was some break-in time, I recall more extension in bass & highs after a few weeks. 
In one of the posts above, nonoise mentions power conditioning: I can attest to the fact that the Marantz likes & appreciates clean power.The amp is revealing enough that you should be able to hear a difference in ac cables: A Pangea will make the amp sound dull and lifeless; the Amazon iron lung jellyfish  (<$20) really opened up my system:
https://www.amazon.com/CableWholesale-10W2-51506-Green-6-Feet-Hospital/dp/B0069FLXLU
There's hundreds of others, I stopped there as I'm satisfied. For now :)

FWIW, I am using the Canare 4s11 speaker wire & Audio Envy interconnects from the Ruby SACD. An Audioquest Powerquest 3 protects all from voltage irregularities. Happy camper here.

Hope you enjoy the amplfier as much as I have mine.