For those looking for more details on the innards of the bda-1, I have some nice pics for you (hosted at image shack). Yes -- the first thing I did was attack it with a set of precision torx drivers and my digital camera
. What can I say -- I'm a bit of a signal processing and electronics nerd -- and now I have created the nerd porn for the rest of you
(I just took the lid off and took pics -- didn't actually touch anything inside.)
For those wondering about the upsampling, they're using the TI (Burr-Brown) SRC4392 for the sample rate conversion -- while it can do any rate conversion from 1:16 to 16:1, they're restricting it to 2x and 4x upsampling. (This is likely wise -- non integer multiples need alot more math done on the signal, and it's very hard to completely avoid aliasing and other problems that can crop up). For those wanting all the gory details on how the re sampling works, Have a look at the datasheets for this chip at;http://www.ti.com/lit/gpn/src4392
Or if you're really adventurous, have a look at the patent covering their technique at;http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7,262,716.PN.&OS=PN/7,262,716&RS=PN/7,262,716
If you look at the pics, you can clearly see how they have separated the digital and analog ground planes -- most signal traces are surrounded by ground traces. (Look to the right of the dacs for the analog signal traces for an example of this.)
Oh -- I almost forgot -- it sounds *amazingly* good. Fantastic precision, detail and control.
(It's connected via balanced cables (canaire 4 star) to a BP-25 w MPS-1, and then with balanced cables to a 4B-ST-Pro. The speakers are PSB Stratus Gold-i, bi-wired with 10 gauge belden speaker wire.) Source is from a Mac Mini, toslink fibre -- digital output on the mini set to 44.1khz -- their available output rates are 44.1, 48 and 96 khz -- the latter two require non integer upsampling and the software that does that on the mac (in OSX 10.5.5) is not up to my standards. The upsampling on the BDA-1 is very very good -- The difference is very subtle -- with it on, the soundstage seems slightly laid back -- with it off, the sound stage feels a bit more in-your-face, and perhaps I'm imagining it, but I also might hear a tiny bit of "graininess" that is not there at all when the upsampling is on -- I'm not sure whether I like it on or off better -- and I can't tell with alot of source material. Clearly I am going to have to do alot more listening
The source material is ripped from CD, and stored with apple loss-less compression.
(for those of you with a mac, go to "Audio Midi Setup" in Applications>Utilities, and set the output sample rate to match our source material -- 44.1/16 for ripped CDs, and 48/24 for almost every dvd. -- I can definitely hear their upsampling when playing through the FrontRow software -- and I don't like it.)
Ok -- here are the pics -- click on them to embiggen