I have been using the digital coax output from my Sonos ZP-80 player into my Altmann Attraction DAC as my main digital source for a while now. The operation and ease of use is great, as is Sonos tech support, as told in my previous review a few months back.
Last night my friend Sol came over to let me hear his new 15W SS integrated amp. It sounds incredible, his best sounding amp yet. When Sol was here we used a CDP as transport so he could spin CDs without ripping. The amp sounded clear and powerful, extremely detailed, yet smooth and musical. I was very excited to spend some time with it listening to my weird music.
After he left, I hooked up the Sonos as transport and was surprised to hear the sound change. More details in the upper mid and high frequencies at first, especially on softer slower material. Recorded tape hiss became more obvious, and massed string sheen was brighter and distracting. But as the signal got louder and more complex, the sound from the DAC was harsher and more etched. On wide open passages it was very noticable. I was tempted to blame the amp, except that it sounded so good just an hour before. Maybe my wife is right - I am crazy???
I had been aware of some edginess in the system for a while. Someone suggested it might be the Altmann's 2134 output stage opamps so I was becoming more aware of it and blaming the DAC. I did not hear it when listening to FM. With Sol's new amp adding significantly more resolution the edginess became more obvious.
Thankfully, I was of sound mind enough this time to remember the 2 different digital transports instead of blaming the amp. This afternoon I compared the Sonos digital output to two different CDPs. My stock Samsung HD-841 universal player, and Sols Marantz CDP. They both sounded identical as transports - smooth, rich musical, no harsh edge, but plenty of detail and texture. The Samsung analog also sounded pretty good playing the SACD layer, but not as good as Altmann on redbook. Putting the Sonos back in, the hyper detailed treble returned along with the annoying edge.
The upside is that the Altmann is exonerated. The downside is I gotta figure out what's up with the Sonos. To be clear, we're talking very subtle stuff here, it took me a year of listening and even 4 g2gs of comparing digital sources before I finally noticed it while using a handmade prototype amp of incredibly high resolution. But ANers listen at this level of resolution, so it's worth discussing. I still intend to buy more Sonos for the house, but I will have to get one souped-up for the hifi.
The Sonos digital output mods from Cullen and Empirical spring to mind, they both suggest that hardware mods really bring the Sonos to life for digital transport. Squeezebox supposedly benefits from digital mods too. Cullen implicates some specific parts in the Sonos that need to go. I guess I'm surprised that any transport is different than any other. But as I continue to learn, in audio everything little thing matters.