[AdamWill]

Well, now I have my HF-1s that cost rather a lot more than my sound card and amp put together, I feel a little upgraditis coming on, and am thinking about getting the Headroom micro stack (in a couple of months, when I'm rich...) as a neat, simple wham-bam-done solution (especially since I run Linux, which more or less rules out getting a significantly better sound card for less than $lots and lots). One thing I found while randomly Googling about the Micro DAC, though, is a thread on Audio Asylum which suggests that it would be 'limited' to 48KHz through the USB connection. The dude sounded like he knew his stuff, so I'm sure he's right, but I have one simple question - does that mean, a la Creative soundcards, it will _only_ do 48KHz and will resample everything else to fit, or does it mean it will do all sample rates _up to and including_ 48KHz? I don't do anything other than normal CDs, so if that's the case then it's fine, but I don't want it to be resampling. (I can always use the optical connection, but then I have to keep my sound card, and I was rather looking forward to my single PCI slot being free for something else). Anyone know?

 

[TheSloth]

It will accept any standard sample rate up to a maximum of 48khz through USB. That is simply due to the bandwidth limitations of USB, and 48khz is the data limit for a USB connection. It will accept higher sampling and bit rates via optical and coaxial connections.

So, yes, 48khz is simply the maximum sample rate via USB, not the only sample rate. There is no upsampling or resampling going on the micro DAC. Just some very sweet digital conversion. Enjoy!

 

[AdamWill]

That's not the explanation the guy on audio asylum gave - it was to do with a specific component in the Micro DAC itself (as a clarification follow-up, he specifically said it _wasn't_ the case with all USB DACs, just the Micro). The USB 1.1 standard gives 11Mb/sec theoretical maximum transfer rate, which does come out around 48KHz uncompressed audio, true, but USB 2.0 gives 480Mb/sec, plenty of head room

. So presumably, at least from a bandwidth standpoint, a USB 2.0 DAC could get way up to 192/24 and higher.

I tell you what, I'll dig out the thread in question:

http://www.audioasylum.com/forums/pc...ages/4309.html

"A few things to mention gleaned from the blurb, since the USB input chip is a 2902, the USB is limited to 48KHz/16 bit, period. The other sample rates, bit depths must be for the S/PDIF input only."

"Hi Ed,
oh no, just the ones that use the 2902 or similar chips are stuck at 48KHz.

Anything that uses the 1020/3200 can handle many different rates and bits, the 2700 series can handle 44.1 as well as 48, and thats just the TI chips. Other makers have the same thing, some run only at 48 others run at multiple frequencies. The 1020/3200 are the most flexible, but they require microcode which generally increases the cost."

 

[Teerawit]

To quote Headroom's website:

"It has a coax and Toslink optical digital input and accepts 16 to 24 bit word length, 44.1kHz, 48kHz and 96kHz."

USB is only limited to 48 kHz because the Micro DAC runs on the USB1.1 protocol.

However, 96 kHz is the limit for optical/coax connections.