Finally, excellent sonics from the computer!
Gordon Rankin on his new Cosecant DAC
Even though the Cosecant DAC was one of the most forward thinking ideas
I ever had, I was still a little apprehensive because of all the talk
concerning how poor computer audio can be. The idea came about after I
saw a headline that reported CD sales down 12% while downloadable music
sales were up 6000%. The light bulb finally lit. Why not make the best
DAC one can find dedicated to the computer, notorious for mediocre sonics?
Basically the DAC has a single digital USB input designed for computer
use with either MAC or PC. USB, unlike SPDIF, is bi-directional and therefore
has error correction and buffering on both sides. Also since this interface
is asynchronous, the clocking problems associated with SPDIF are abolished.
computer power up, the 2 devices negotiate services. In this case the
Cosecant DAC tells the computer it can do 16 bit audio at 32K, 44.1K and
48K. Since the USB receiver only has to handle these 3 frequencies, the
clocking to the DAC has almost no jitter. SPDIF actually has to
be synched to the exact frequency of the transport (i.e. if the transport
is working at say 44.0896K instead of 44.1K the DAC has to sync to that
frequency). Therefore the jitter problems of SPDIF almost go away. So
we have a zero error protocol to link the computer to the DAC and very
The Cosecant is platform and operating system independent. In other words,
any Mac or PC based computer that has USB output will be able to hook
up to the Cosecant DAC without software drivers. Just select the Cosecant
for Audio Output in your system preferences or control panel and you're
That's right you can now do any of the following:
- Use the CD drive as a transport and play
- Use your hard drive as a media storage
- Stream Internet audio (i.e. FM stations
- Video audio output
- Use the DAC as a monitor for computer
In designing this product I looked at many
available USB Audio DAC chips. The offerings really did not excite me
much as most of them where one bit Sigma-Delta units. So I stuck with
the Transcendental DAC we use in our own Cosine. There was no need for
the Caffeine options since jitter was so low. This DAC is basically a
multibit 16 unit with passive I/V and does not have any analog or digital
filtering. It also does not adhere to up/oversampling.
The tube output does filter the output in its own way and the MagneQuest
transformer coupled output assures both isolation and good drive capabilities.
So we use a USB receiver for this DAC to our Transcendental DAC technologies
to the 6GM8/ECC86 tube with parallel feed transformer output.
How do we optimize the computer
First, we make sure that all the importing is done with AIFF format. This
is usually a parameter in the configuration of the application you are
using (i.e. preferences in Apple's iTunes). Also there are usually items
in the configuration such as error reading, recovery, and buffering size.
Always set the parameter for error recovery when reading audio CD's. Be
sure to set the buffering to the highest setting to allow for the larger
AIFF files. AIFF is lossless encoding, much like zipping an audio file.
The data take in is the same as the data output.
Got your curiosity up? More questions?
Drop by Wavelength
3703 Petoskey Avenue
Cincinnati, Ohio 45227
(513) 271-4186 ph.vm.fax
East Bristol Street Philadelphia PA 19124 USA
Voice: 215-288-4816 Fax: 215-288-4816
© 2004 MagneQuest