Just bought an MU-1. I've only had it 36 hours so I'm going to refraim from drawing conclusions but initial impression is very, very positive.
I spent most of the morning reading this thread quickly and there is so much information in it that I had to skip over some of the bunny trails it goes down and will probably go back through it a bit later. But great info here. I especially appreciated the discussions by @nyev and @ghasley .
My old streamer is an Innuos Zenith MkIII. My DAC in a Chord DAVE and with the old streamer I use the Chord M-scaler so count me in the pro-upscaling camp. I'm not going to sell this gear yet as initial impressions can fade. I'll put it back in service in a week or so and that should confirm. Of course with the MU-1 I don't use the Mscaler. Interestingly I was able to remove the following equipment from my rack: 1. Innuos streamer. 2 Chord Mscaler. 3 NUC with Roon core running on it. 4. Farad LPS for M scaler. 5. LPS for NUC.
I don't have a good AES cable so I'm listening to a $50 amazon cable I could get overnight. I decided last Sunday to look at the Grimm. 60 minutes later I decided to try one, and 2 hours later I had bought one used. It shipped Monday, arrived Wed, and I'm posting this on Fri. I have a better cable from DH Labs coming tomorrow but will look at higher end cables. But just the step up to DH Labs from amazon should be big.
I pulled the fuse and the Grimm has a 500mA input fuse which is very small (sizing of fuses by OEMs is more Kentucky windage than science). It is my opinion that this one is sized very tight to the load (even though the load is very small). That's the long way of saying that I recommend a fuse upgrade. I upgraded the fuse this morning and the improved detail and dynamics was obvious.
I'll post more after I've had more time to listen. I updated my system in my profile this morning so you can see what other gear I'm running if you care.
Jerry