Hi,
I2S is a standard for digital audio, originally made by Philips and Sony back when they put together the CD format. It's pretty straightforward. A word clock starts out 0 for the left sample, then goes to 1 for the right sample. Digital data is transferred MSB-first on the edges of the bit clock. The number of bits may be almost arbitrary, since a DAC stops latching after it has received its share of bits for its resolution. The tricky bit about I2S is that it's synchronous with music, and more importantly that a "dead tick" occurs after a word clock edge, before the MSB of the next sample. To make things more complicated, if all bit clock ticks are needed to convey audio samples (what I call "bumper-to-bumper" I2S), the LSB of the previous sample is transmitted during the "dead tick".
What this boils down to is that I2S is straightforward between audio equipment which has it enabled, and a major hassle for MCU designers who try to fit it into existing serial port hardware.
I expect built and tested hardware in about two weeks, crossing my fingers that everything works out.
Cheers,
Børge
I2S is a standard for digital audio, originally made by Philips and Sony back when they put together the CD format. It's pretty straightforward. A word clock starts out 0 for the left sample, then goes to 1 for the right sample. Digital data is transferred MSB-first on the edges of the bit clock. The number of bits may be almost arbitrary, since a DAC stops latching after it has received its share of bits for its resolution. The tricky bit about I2S is that it's synchronous with music, and more importantly that a "dead tick" occurs after a word clock edge, before the MSB of the next sample. To make things more complicated, if all bit clock ticks are needed to convey audio samples (what I call "bumper-to-bumper" I2S), the LSB of the previous sample is transmitted during the "dead tick".
What this boils down to is that I2S is straightforward between audio equipment which has it enabled, and a major hassle for MCU designers who try to fit it into existing serial port hardware.
I expect built and tested hardware in about two weeks, crossing my fingers that everything works out.
Cheers,
Børge
Thanks for answering now i know something...so if all goes well...what parts you recomend to buy(DAC+USB -I2s) ....MY pc is following...
http://www.diyaudio.com/forums/pc-based/215731-pc-music-transport-25-a.html
V
Well, my obvious recommendation would be to buy the AB-1.2 from me. That's a boxed and tested USB DAC. Follow the link in my signature for more info.
George also offers hardware based on the same firmware. George, which are your offerings at the moment?
Børge
George also offers hardware based on the same firmware. George, which are your offerings at the moment?
Børge
Yes, it uses I2S. The USB-I2S module uses our firmware to be a USB device and I2S master. The module sits on an analog board which generates clocks and is I2S slave.
If you follow my signature and click around a bit you'll see plenty of schematics.
Børge
If you follow my signature and click around a bit you'll see plenty of schematics.
Børge
The boards are being manufactured as we speek. I hope to have them in Norway in 1-2 weeks. Shipment to the US would add another 1-2 weeks days to that.
Børge
Børge
Hi, just to ask if any body here has, by any chance, these three devices: an Ipad + Camera connection + USB DAC QNKTC
I'm curious to see if it works this DAC with Ipad as a source. Some DAC's do, but I'm afraid it has to be not self powered DAC... but I haven't seen much about it.
Here is a link with the discussion:
List of DACs that work with iPad
Thannks
I'm curious to see if it works this DAC with Ipad as a source. Some DAC's do, but I'm afraid it has to be not self powered DAC... but I haven't seen much about it.
Here is a link with the discussion:
List of DACs that work with iPad
Thannks
I think you misunderstood the site you linked. Many DACs will work with self-power.
By the way, in USB terminology, "self powered" means external power. "bus powered" means USB power, i.e. from the iPod dock.
Hi thanks for correcting... sorry.
What I mean is something like this:
http://www.head-fi.org/t/491308/ipad-with-udac
http://www.flickr.com/photos/nokton/4621172765/
I don't understand what type of bus powered DAC is needed to connect with an iPad via camera connection kit. The pictures from flickr is exactelly what I what out from QNKTC DAC... if possible.
What I mean is something like this:
http://www.head-fi.org/t/491308/ipad-with-udac
http://www.flickr.com/photos/nokton/4621172765/
I don't understand what type of bus powered DAC is needed to connect with an iPad via camera connection kit. The pictures from flickr is exactelly what I what out from QNKTC DAC... if possible.
Last edited:
Hello, I have a question... Is it possible to use 176.4khz or 88.2khz sampling rate at windows7?
Hi!
I have this issue with SB Touch (Triodes kernel) and the AudioWidget. If I set the widget to UAC2 I get 48khz, when running in UAC1 mode I get 44,1khz but a lot of noise (pops and sparkles). Anyone solved this issue?
Brgds
I have this issue with SB Touch (Triodes kernel) and the AudioWidget. If I set the widget to UAC2 I get 48khz, when running in UAC1 mode I get 44,1khz but a lot of noise (pops and sparkles). Anyone solved this issue?
Brgds
More info:
The widget has the latest code as of 20120519 and is a pcm5102 type by George. I finally got a machine with Win7 and the WidgetControl seems to work every time 🙂
I dont have this issue with Georges 9023 or Börges AB-1.1 (older code).
Brgds
BTW: What is the difference with latest and main firmware versions? The size has jumped up considerably lately...
Last edited:
Our ASIO uac2 driver by Nikolay supports 44.1/48/88.2/96/192. 176.4 is disabled at the moment. I think Nikolay is keeping that for DSD in future.
Alex
Accidentaly used usbi2s instead of usbdac - works now in uac2 mode and I suspect uac1 will work as well!
Brgds
Ground isolation - we need it!
Interesting measurements (on another USB/I2S interface) showing the importance of GND isolation:
exaU2I - Multi-Channel Asynchronous USB to I2S Interface: Ground isolation - with and without
Interesting measurements (on another USB/I2S interface) showing the importance of GND isolation:
exaU2I - Multi-Channel Asynchronous USB to I2S Interface: Ground isolation - with and without
Indeed. That's why I am eagerly awaiting the next version of audio-widget with i2s isolation 🙂
I get suspicious when I see inadequately documented tests. The grounding they used (1Meg resistor?) can cause some USB problems and the measurement suggests there were more than one path between the computer and the audio system. The assumption that removing the ground will make things wonderful can easily be tested by using a laptop on battery. That is as isolated as possible, but there are reports its not enough.
Meanwhile good isolation is not simple. I started on a design to work with the Audio Widget. I'll see if I can find it and share it. The bigger issue is powering the isolated parts.