Posted by bcherry (M) on August 19, 2010 at 20:29:28

In Reply to: RE: State of the Union - Asynchronous USB DAC - Caveat Emptor posted by Thorsten on June 29, 2010 at 11:53:08

192KHz/24Bit – When It Is and When it Isn’t:

There seems to be considerable confusion what "192KHz capable asynchronous USB DAC" really means. To make sure you get what you think you're getting, please consider the following.

192KHz/24Bit is easy to explain: end-to-end 192khz/24bit data stream. 24/192 in>>>24/192 out

1.DAC chip:
It is a device that capable to accept a digital audio data stream at a sample rate of 192KHz and with 24 Bit word. Such a device is capable of very wide dynamic range, in theory 144db, in practice >110db.
If you are buying a "24-Bit" DAC expect better than 110dB Dynamic range for the actual DAC Chip. If it’s not…it isn’t

2.USB:
The data stream must pass through the DAC USB chip subset which also must be 24/192 capable. Most aren’t and if they aren’t, the 24/192 DAC is wasted. It isn’t.

3.USB Driver:
If you want 192KHz/24Bit to work properly across the 24/192 capable USB you have to write your own driver for Windows and OsX. So, if a USB DAC claims to be 192KHz/24Bit but does not come with its own Driver CD -- it isn’t.

4.Asynchronous:
Just as important to high quality music as delivering a bit-perfect 24bit
192khz data stream is the role of the clock.

The USB audio device needs to have its own on board audio clock and not be linked to the PC Source for its clock (when the DAC is clocked by the PC this is called synchronous mode).
Unless the implementation is asynchronous, we won’t realize the performance the 24/192 device is capable of delivering.

Verified Asynchronous USB Audio Devices (at this time):
Ayre QB-9 DAC - based on the Wavelength Audio Streamlength System, limited to 96KHz
Diy Hifi Supply Cleo & Morello based on heavily modified Musiland Digital Cores with new power supplies, clocks, tubes output stages etc., 192KHz/24Bit, ASIO, WASPI, WDM...
M2Tech Hiface and related devices - the original HiFace draws power from the computer, has not so great clock implementation and lacks ASIO but does 192KHz with its own driver
Musiland Monitor Series - very good software and digital hardware implementation, shame about the rest, 192KHz, ASIO, WASPI, WDM
Wavelength Audio Streamlength based DAC's, limited to 96KHz
And others…

Beyond the 4 points above it comes down to the art of implementation -- when and where to include tubes, power supply, clock quality, impedance matching, eliminating bounce artifacts, and all the little touches like parts quality etc etc that are difficult to quantify but can be heard.



DIY - Done Right!