Pros: Outstanding sound quality, extremely high value, solid construction, no compromises design
Cons: May be too large for some people, requires a 30-60 minute warmup to sound its best
In a nutshell: if you are looking for a multibit chip DAC, in this price range there is nothing that even compares to the Audio-gd ACSS line flagship. If you find the term multibit confusing, search the forums for "Delta Sigma vs Multibit" (they are two competiting DA converter chip architectures). Using 8 expensive R2R PCM1704UK DAC chips in a balanced configuration and a proprietary DSP with fantastic performance (in the latest V5 update!) in a no compromises design, it´s in its league of its own. According to many it can compete with gear way over double its price, but this of course depends on your subjective sound signature preference.
DESIGN & BUILD QUALITY: three R-cores, discrete design etc. Actually just take a look at the internals of the box and compare it with any western DAC the same price range. It really speaks for itself. The REF7 is a fine example of perfectionist engineering taking no compromises. The aluminum case is sturdy and utilitarian, but isn´t ugly either. You´re paying for what is inside and that is really something special. It´s hard to overstate the value of this product. Arrived in perfect condition. The only minus I can think of is that it´s too big for some people, for example if your audio gear is on your computer desk. Another is maybe that it requires a 30-60 minute warmup to open up the sound. But believe me, it´s worth it :) Some might find the looks too ulititarian, but a prettier chassis would bring the price up...
VALUE: off the charts. Western companies cannot compete in the same price range. A truly unique product - Audio-gd is one of the very few companies in the world that offers affordable PCM1704UK chip based gear. Best audio purchase I´ve ever done.
AUDIO: superior resolution, imaging, huge rock solid soundstage and a pitch black background. Never sounds digital or harsh like most Delta-Sigma DAC products. Very natural sound with the best bass performance I have ever heard - goes extremely deep and controls everything with an iron grip. The take no prisoners design attitude shows here.
On the negative side, it is not a very forgiving DAC. If you are going to play bad recordings, the REF7 will sound bad. But play some Diana Krall, Mark Knopfler or Pink Floyd, and it will sing! Some also might want a bit more dynamics in the sound, and more punch in the bass. The R2R sound has a touch of nostalgia, it´s richly textured and effortless, but at the same time it does not have the Delta-Sigma sense of dynamics. Then again this DAC has none of the digital harshness Delta-Sigma type DAC´s so often exhibit.
Everyone knows the law of diminishing returns. For me the REF7 is the sweet spot. The price/performance ratio here is exceptional, and for me. I no longer think about upgrading this part of my chain at all. That´s the highest praise a DAC can get.