What are your impressions of MU1 internal DAC vs external DAC? I believe, I read somewhere that you were using a Total DAC, is that still the case?
The MU1 doesnt have an internal dac, it is a D to D only via an AES/EBU connection to a dac. Yes, I have a Totaldac D1-Tube-Mk3 which has three dac ladders per channel and a two tube 12au7 output stage. I have played around with the Grimm upsampling at 4fs, 2fs and then disabled. It sounds quite good with each and its really dependent on the recording. For instance, I happen to almost seek out a well recorded 16/44.1 recording over some (I repeat, SOME, not all) higher resoluton versions of a given piece of music. It seems there is something really special when the Grimm gets ahold of a really good 16/44.1 file and runs it through its 4fs upsampling and outputs it to 24/192. Quite special to my ears.
Seriously though, I went through all the right brain, various iterations of the options and I have just left it on 4fs and forget about it. I just listen and enjoy these days.
Indeed, the Merason utilizes two Burr Brown 1794a dac chips in dual mono. To many ears it competes well with well executed R2r ladder dacs. I mentioned it as a very well built but no frills non-oversampling option with an excellent output stage for very reasonable money. At least it used to be very reasonable money at ~$5k...its now an $8k dac.
The Grimm firmware updates are well done, you are correct. I must admit though...I just dont hear "night and day", "a veil has been lifted", "my wife walked into the room and asked what I had changed", "my jaw dropped" kind of comments I read all too often. It just sounds great. BUT....so did the Aurender I demo’d and while the Grimm MU1 clearly outperformed the Innuos Zenith Mk3 that I owned at the time, I was never unhappy with the Innuos. In my system, I appreciate the Grimm remote volume implementation almost as much as some other independent components as my amplification of choice doesnt have a remote volume control.
Some rumors of the MU2 are a little off the mark. I have heard, although unsubstantiated by anyone with good knowledge, that the dac section for the MU2 is (once again, rumor) being contributed to by Bruno Putzey of Mola Mola Tambaqui fame. Evidently they are good friends and have collaborated in the past.