Pros: Great, un-coloured sound, plenty of options, solid built, doubles as a DAC, plenty of digital I/O, balanced output, fantastic DSP.
Cons: Some may find the sound a bit boring. Threatened by newer DACs so best value second-hand.
I hadn't intended to get this. I was offered it in trade for my HD-800s (plus cash), which, out of curiosity, I ended up agreeing to.
I hadn't great expectations as I'd heard some less than stellar comments about the DacMagic from people who had a lot of gear experience. However, I was most pleasantly surprised when it arrived and I plugged it into my Audio-gd Phoenix, that it shared much of the "just the music" presentation of my Audio-gd Reference 1. More usefully, no matter how I connected it digitally, from optical straight from my MacBook Pro (usually the worst option) or via the Audio-gd Reference 3 re-clocking and up-sampling digital converter, I haven't been able to detect a significant difference in the quality of the output when used as a DAC.
I'm still experimenting with settings to see if I can detect which, between the 840C and my Audio-gd units, can handle up-sampling and dither best, something made all the more difficult as turning on up-sampling lowers the analogue output volume.
The good sound is no doubt due to the excellent DSP which handles the up-sampling and other features, leaving the actual DA chip to do only the minimum. DAC makers are only just waking up to the critical importance of the digital input, moving away from the less than great options, especially for USB input (read: DacMagic's crappy USB input) and taking more care to get this right from the start (eg: The Ayre DAC).
I have no doubt that this is one of the key reasons this CD player sounds so good, alongside the solid case and well-thought-out electronics. The output stage, though containing a number of OPA2134 OPAMPs which, in typical cheap DACs presents a dull and lifeless sound, have been incorporated in a manner that the output doesn't sound like a typical OPAMP-driven circuit at all. Someone with more knowledge of these things will have to explain why this is, as I don't understand it well enough.
Ultimately, if I were to fault it, I would share the conclusions of Hi-Fi Choice's review. Some may find it un-musical, if neutral is not your cup of tea in your source components. It has a slight treble-boost in the sound, not readily noticeable without careful comparisons with other gear and it isn't anything like the very sharpest, detail-wise. However, it does manage to be feature-rich without compromising the sound and a good investment for headphone listening.
From time-to-time the 840C shows up second-hand for considerably less than its retail price. That makes it a serious bargain in my book. It will slaughter the popular choices such as the Benchmark DAC 1, Lavry DA-10 and others without a doubt, but may be fighting an uphill battle with the newest Sabre32-based DACs around the same price new, such as the Wyred DAC 2 and Audio-gd units, as it is a few years old now. I've given it 4 stars for value as a result -- 4 stars new, and 5 stars second-hand.