USB to simultaneous data (or I2S) board

Now it is decided, we will release this project. At this moment I brought the PCB layout to a close, and we will complete the design, produce required quantity, and ship all the orders in the late November or the first half of December.

The goals of this design remain as explained in the original topic. So, this board is essentially a USB decoding stage, which also provides clock signal for D/A conversion. It means that at one side it connects to PC via USB port and, by operating as asynchronous (master) USB Audio Class 2.0 device, it accepts up to 192 kHz sampling rates. On the other side it outputs “raw” PCM signal, in Philips simultaneous data, or I2S form, that can be sent to D/A chips. Also, it provides galvanic decoupling in between.

Here is the block diagram. Please click on the picture to see it full resolution.



Simultaneous data protocol can be used exclusively with TDA1541(A) (and with TDA1540 if it is 14 bit), and I described its advantages in this post. This protocol has separate left and right channels data lines, and since this board will also output inverted data signals, and will have two BCK and two LE (Latch Enable) connectors, it can be also a source for real balanced TDA1541A DAC.

Alternatively, the output can be more common I2S protocol, with additional 75 Ohm BNC S/PDIF.

Practically speaking, the major difference between two options makes the firmware. Either board can be also reprogrammed later, and there will be several ways to do this, and the most radical option would be to replace flash memory chip with another one. We can also ship additional flash chip with alternative firmware with any order. This chip is SOIC-8, supposedly not hard for soldering for any serious DIY-er.

The board needs one 8-10 VAC transformer i.e. secondary winding, to feed the audio clocks and reclocker. I have given up of providing the option of connecting the whole board supply to USB +5 VDC Vbus, as it would compromise the design, and is probably not what many owners will actually want to use anyhow.

The output can normally drive reasonably long cables, up to 50 cm or so, and several gates, but it is not meant to drive terminated lines. Model S MkIII users who possibly want to use this board with it are welcome to contact me on this matter. S/PDIF output stage is of course different, and it includes discrete buffer.

Clocks are AVX SMD cans, and frequencies are 22.5792 MHz and 24.576 MHz. For simultaneous data mode it is possible to use lower frequencies, and on demand we can install 11.2896 / 12.288 MHz pair instead, so please specify if you want these when placing an order. Please however note that the 22.5792 / 24.576 MHz are required for full hardware compatibility with I2S & S/PDIF option, namely with 11.2896 / 12.288 MHz an S/PDIF output will not operate at 176.4 kHz and 192 kHz sampling rates. Selected clock frequency is also available as master clock (MCK) output, which TDA1541A users normally will not need, unless they want to experiment by clocking it directly – the old non -A version via its “system clock” input pin (4), or later -A version via adequate frequency divider.

The other parts you will find on this (usual Audial white) 95×105 mm board are XMOS processor (128 pin), common mode passive supply filtering, Schottky rectifier, low noise discrete regulator, VHC logic, NP0/C0G capacitors for critical local decoupling, etc.



Driver for Windows 7/8/10 will be provided, whereas Mac OS X and Linux are USB Audio Class 2.0 compliant, so they do not need a driver.

The board is available as ready made module only, and price per unit is € 150. Additional firmware flash chip is € 10. Shipping and handling fee is € 17 (Airmail, registered and insured), and it is charged once per order, regardless of Qty. We accept PayPal and bank wire transfers.


Edit 30/10/2016: PCM1704 format is added as an option in the ordering form.

Edit 06/11/2016: Added instruction manual preview.

Edit 11/12/2016: The whole project took a few weeks more than originally planned, but the next week we will start producing a series of these boards.

Edit 05/01/2017: Added instruction manual revision 0. The boards are now shipping. Ordering form is now closed, but in the second half of January we will make somewhat more samples.



  Instruction manual rev. A




Related topics:

USB to simultaneous data or I2S converter, series 2

USB board Mk3 and AYA II revisited (proposal)



105 Replies

  1. 03-10-2017

    Hello Frederick,

    Windows audio is still generally limited to 192 kHz. For playback at 352.4 kHz and 384 kHz you have to use ASIO or WASAPI output.

    BTW, it looks like Windows support for USB Audio Class 2.0 is finally on the way. Once it is included in regular Windows release or update, Audial USB board (and Model S USB) should work natively, as plug and play device. For most of you it will be probably simpler just to connect device than to install dedicated driver. Still, firmware update surely won’t be possible without dedicated driver though.


  2. 03-10-2017

    Well, after I’ve sent the post above, I thought I could check if Windows is maybe already regularly updated to support UAC2. So I uninstalled usual driver, and Windows started its own procedure to recognize the device, and… it apparently works.

    So, this is significant and good news: this USB board is now plug-n-play device in Windows.

    This applies to Windows 10 (build 1703), and this feature comes by regular update. So, everyone using Windows 10, who did not trick it to ignore updates, might already have it too. (In Win 10 it is normally not possible to disable updating, but it can be worked-out for instance by setting WiFi as metered connection.) At the moment I am not sure about previous versions.

    More details to come.

  3. 04-10-2017

    Hello Pedja,

    One good news or side effect with the higher sampling rate FW update is that it fixed the issue of not getting Spotify to directly stream to the USB Board. No need now to use the Jriver’s WDM driver – it now streams Spotify directly.. Thanks Pedja.


  4. 18-04-2019

    Hello Pedja,

    I would like to know if this board can be used with the Marantz CD94II which has a separate dac board with two TDA1541A in complementary mode.

    If so: is your board still available for ordering?

    Where can I find all specs of the board?

    Johan Maessen

  5. 03-05-2019

    Hello Johan,

    It is generally possible to use this board with any TDA1541A based D/A section, whether for the single end, or balanced operation.

    You can find the instruction manual link (PDF) above, in the initial post. It includes the performance data too.

    However, all the boards we made are sold out.


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