I have been testing all sorts of playback devices and have been surprised to find that I seem to get the most pleasant sound quality out of a Mac Mini with a USB cable directly connected to my DAC, using Roonbridge in exclusive mode.
The sound quality is very pleasant: no harshness, space and depth, natural sounding, etc…
This is surprising as it goes against some of the beliefs I held:
OS is High Sierra, which is not particularly “optimised”
no fancy usb reclockers/filters between the player and the DAC
I do have the Uptone Audio kit installed on my Mac mini (mid 2010 model) and use a linear power supply
My DAC does not use the USB power.
I have a shielded rj45 cable with a grounded switch (à la Swenson).
But I do not even feel any of those little tweaks explain the results.
Would be interested in hearing of other’s experience in the matter.
My DAC is the EC Designs Mosaic UV. I have a hypex stereo amplifier, and Harbeth bookshelf speakers.
I setup my audio system with Roon about a year ago. I have a Mac Pro 2010 as the core and a Mac Mini 2012 as the endpoint with USB out to my DAC as in your configuration. The Mac Mini took a dive about 2 weeks ago and I’ve been using an iPad Air 2 as the replacement endpoint while I try to figure out where I want to go with a new permanent endpoint.
The iPad sounds surprisingly good to me (as did the Mac Mini), but I’m not happy about the inconvenience of having to wake it and launch Roon every time I want to listen to music. I’m only interested in endpoints that do not have a built-in DAC because I’m happy with mine. My research brought me to the ultraRendu, the sms-200 ultra and a replacement Mac Mini.
I have not demoed the ultraRendu or the sms-200 ultra, but I’m curious if you have and could compare either of them to the sound of your Mac Mini endpoint. I feel the same as you regarding the sound quality of the Mac Mini endpoint. For all the reasons you mention, it shouldn’t sound that great but it does (at least to me)!
I already keep the iPad’s display set to never sleep which is doing the same thing. I always shut off the iPad manually when finished for the session to prevent the screen from burning. Is that not an issue on the iPad’s display (iPad Air 2)?
I can’t speak for John S of course but I have learnt a lot from him and I would guess this (quoted) is a big reason for your observations, more-so than the Mac Mini itself.
I noted very similar observations as you when I once had my NAS (Linux) acting as both Roon Server and USB source, with a direct USB cable connection to my USB DAC.
With the stock SMPS it sounded very bright but when I took a 12Vdc linear PSU from somewhere else in my system and used it with the NAS, the sound was noticeably smoother.
One reason may be due to linear PSU’s typically not having, what John calls ‘high impedance’ leakage currents and typically having low levels of low impedance leakage currents. Whereas he has found SMPS’s that he’s tested have both high and low impedance leakage current components.
Again, this was a direct USB connection to my USB DAC in my setup at that time. When I later moved the NAS to the other side of the house, using the linear PSU to power it was a waste.
But overall similar observations to you, regarding using a linear PSU to power your USB source.