USB to simultaneous data or I2S converter, series 2




Another series of USB to simultaneous data or I2S converter board, which was originally released previous year, will be produced during the next few weeks.

The information about this design is mostly already posted into the original board topic (please have a look also at its instruction manual), so to avoid repeating the things already told, here are only the news brought by this version.

The first change is, this board will have fully local supply (a.k.a. “self-supply”). Previous version had its own local supply for clocks and reclocker circuits (of course), but this version will introduce local supply for USB decoding part as well. The actual benefits of such a solution is still a matter of debates, but it has one practical advantage anyhow: it makes the unit reset easier. As for performance benefits, it must be noted that this change does not bring measurable differences, leastways not in jitter domain. But, in order to achieve the highest possible sonic performance, here we are faced with one huge upcoming topic, and which we will discuss soon openly: it is about this and similar PC audio things, such as USB cables and conditioners, or PC software, that we still can not capture by measurements, but we can hear. (And which recalls the old topic of CD transports sonic qualities.)

Of course, this version hence requires two transformer’s secondary windings, one for USB side, and another for clocks, and they both can be anything between 7 and 11 VAC.

And second change is, other than as ready made module, this version will be also offered as ready made device, in anodized aluminum chassis with Audial logo (chassis designing is in process, estimated size is 20 x 12 x 5 cm), and with BNC connectors at its output PCM side.

Modules will be however still equipped with U.FL connectors. They will also have BNC footprints, but these will be left unpopulated. Generally, U.FL are fine as PCB connectors and wiring between the boards, while BNC are more convenient for external use.

The picture below shows the block diagram of this version of the board. Click on it to see it full resolution, please.



Output format and master clock frequencies

With TDA1541(A), a simultaneous data protocol is highly recommended. Lower master clock frequencies do sound a bit better, and in simultaneous data mode a 11.2896 / 12.288 MHz clocks are adequate for full compatibility with sampling frequencies up to 192 kHz.

In I2S, an 11.2896 / 12.288 MHz clocks will work up to 96 kHz, and for up to 192 kHz compatibility a 22.5792 / 24.576 MHz frequencies are necessary.

In addition, this board can output the PCM1704 format. In this case an 11.2896 / 12.288 MHz will work up to 192 kHz, however 22.5792 / 24.576 MHz will make it hardware compatible up to 384 kHz, and this compatibility might be enabled by future software updates.

As before, the output format is set by firmware, but additional firmware chips will not be sold at this time. Firmware chips sold with the first version of USB board will however work with this version too.




The USB to simultaneous data or I2S converter, series 2, is sold out.



  Instruction manual (Revision 0)




Related topics:

USB to simultaneous data (or I2S) board (2016 release)

TDA1541A and Model S USB, part 2: Simultaneous data mode

High resolution audio, async USB, oversampling, upsampling and stuff: The current state of affairs


42 Replies

  1. 12-05-2017

    Hi Pedja,

    would you recommend 50 Ohm or 75 Ohm connection (bnc) for simultaneous data transfer?

    Best regards

  2. 15-05-2017

    Hello Tobias,

    There is really no general preference towards either of these. In my view, and for our purpose, 50 Ohm BNC is more common, while 75 Ohm line is (a bit) easier to drive, but that is all. What really matters, once you decide to control the impedance, is to keep the whole line as close as possible to supposed value, whether it is 50 Ohm or 75 Ohm.

    So, with 75 Ohm receiving unit, such as Model S Mk3, it should be 75 Ohm, and with receiving unit that is 50 Ohm, this unit output should be 50 Ohm too.

    Still, we have here four lines, each carrying one signal, and while it can be welcome, the benefits of controlled impedance in this case is not that huge as, for instance, with S/PDIF.


  3. 24-05-2017

    Nice that there is second run! Will this version allow a firmware change by the user through USB, jtag or other?

  4. 26-05-2017

    Hello Berny,

    It is always possible to flash the firmware by JTAG programmer, since both previous and this version of the board include necessary connections.

    As for the update via USB connection (DFU), I need to make a couple more checks, but this time it will be most probably possible to do this too.


  5. 26-05-2017

    Updatable by USB would fantastic news! I suppose you will make availble to the buyers the different firmwares in that case…? Look foreward to this! Regards

  6. 27-05-2017

    In case you are referring to the output format, yes, among the other things this feature would also make possible to change it.

    Still, please note that this way it is not possible to fully load the firmware, but only to “update” it. And, since there would be too many possible output format migrations (six, precisely speaking, times two, as we have two master clock set-ups), only the most typical migrations files would be ready available, while the others could be provided on demand.


  7. 02-06-2017

    I received several inquiries, and here is the information for those who would want to use this board with TDA1540 (14 bit) or with PCM1702 (20 bit).

    These chips use right justified protocols, so Latch Enable has to be positioned with respect to the end of the binary word. It means that the TDA1541A (simultaneous data) and PCM1704 firmware should be changed so the LE is moved to the left for two, and four bits, respectively. This is not hard to do, and can be done on request, and I can of course verify the output by the scope (and provide the screenshots), however I can not verify this with actual DACs, simply because I do not have them at hand.

    Regarding the project itself, the ordering form will remain open for the next few days, and then we are going to start production.

  8. 11-06-2017

    Sorry for this repost but I’m not sure if anyone is monitoring the series 1 blog.

    I was wondering how hard it would be to convert the series 1 into a series 2 board? If you had a clean 5v supply what would be the best – simply tying in the 5v at the usb header pin or maybe using the +/- points after FB1U1 (see underside of board)?

    Thanks 🙂

  9. 12-06-2017

    There is a bit more about actual supply re-wiring done in series 2.

    As for your idea, I have never tried it that way, but it might work too. I will try to check it tomorrow.

    (If it does work, I would skip that ferrite bead.)


  10. 12-06-2017

    Thanks Predja

    I appreciate the reply and the effort. I was thinking of using one of the spare 9v lines I had in conjunction with the onboard PSU for one of the unused supplies. So it should be stable and clean.

    Excited to hear what you find.


  11. 13-06-2017

    So… I will still have to look into details, but for now I can report that the idea generally does work.

    Regarding the supply that can be used here, please note that you need here completely separate supply, in a way it is galvanically isolated from both the rest of this USB board and the DAC. So, if you use some of AYA II on-board regulators for this purpose, you will have to cut the AYA PCB ground, to disconnect given regulator ground from the DAC ground.

  12. 14-06-2017

    Thanks Predja

    I’m thinking either the unused SPDIF input stage 5v regulator circuit or a standalone shunt regulator (Salas Reflektor maybe which may be a bit of overkill here).

    If my understanding of the AYA SPDIF input stage is correct then the ground there is completely separate from the USB and power grounds and is only connected when the stage is in use via the relays – right?



  13. 14-06-2017

    Actually, what you said applies to the AYA II USB section. At the S/PDIF stage, it is only the input transformer primary side that is decoupled from the rest of the DAC (C205 put aside), while its circuit and supply ground is always connected to the DAC ground.

    Also, please note that this USB board front end requires +5 VDC, and it draws 110 mA (typically), so the regulator should be scaled accordingly.


  14. 16-06-2017

    Hi Pedja,

    What exactly is provided if you purchase a module. ie PCB with xmos chip soldered and flashed.
    Are all the passives, crystals, silicon, etc included?

    Sorry maybe it is mentioned somewhere already.



  15. 17-06-2017

    Hello Ryan,

    Yes, a module is also practically a working device, that takes two transformer secondary windings to operate. It does not include only BNC outputs.


  16. 28-06-2017

    Hi Mr. Rogic:

    The USB to simultaneous data or I2S converter, series 2 board is available? If yes, please let me know how to purchase it.

    Best regards,

  17. 29-06-2017

    Hello Antonio,

    You have mail.


  18. 16-07-2017

    We are about 15 days late with respect to the original schedule, but now everything is set for manufacturing, and series will be produced during the upcoming week.

    Of course, everyone will be informed prior to shipping.

  19. 23-07-2017

    One of the requests I have been receiving as this project was developing was from previous AYA II owners: some of them wanted another AYA board, so they can make real balanced TDA1541A DAC.

    So, here is the offer: during the next 7 – 10 days I will accept orders for AYA II (DS). You can order either bare or populated board (it can be with or without its own front ends, i.e. only DAC part), and transformers, so it is basically the same offer, as when AYA II DS was originally released.

    There will be no online ordering for this item, so to place an order please use the contact form.

  20. 25-07-2017

    Hi Predja

    If I can be forward and make a suggestion – why not release a SPDIF splitter for a balanced TDA configuration? It could nicely tie into the UFL connectors for the SPDIF input on both of the AYA board.

    I’m not sure if it would be warranted or the demand would be enough but after much searching there doesn’t seem to be a off-the-shelf solution I could find anywhere. I’m actually busy assembling the arts based on your schematic published elsewhere on this site.


  21. 27-07-2017

    Hello Brent,

    I understand the point, however for the time being I do not plan to release new DIY items or projects.


  22. 04-08-2017

    hi Pedja,

    please see your personal email. Thanks!

  23. 05-08-2017

    Hello Philip,

    Reply sent.


  24. 09-08-2017

    Hi pedja

    I have a PCM 1704 .homebuild dac
    And would like to use the version 2 USB module for it.

    How to order?

    Br Kurt

  25. 09-08-2017

    Hello Kurt,

    You have mail.


  26. 09-08-2017

    And now, for official information of the state of this project:

    The boards are produced, and now I am checking some details prior to shipping, which will start the next week. We will ship firstly the modules, and then completed units.

    And, here is the picture of the board. This one was taken prior to through-hole parts mounting, so what you see are SMD parts only – but they are the majority of the parts though.

    At left, you will notice some USB decoder supply parts, added in this version. At right and bottom right area you will notice some unpopulated SMD parts too: these are the buffers that drive BNC outputs, and their own supply.




  27. 09-08-2017

    Nice looking card!

    Can’t wait trying out this “simultaneous” thingy and see, or rather hear, if I can detect any differences from I2S.

    Thanks for making this available to DIY’ers.


  28. 08-09-2017

    By now, the modules are mostly shipped. We still have to ship completed units, as well as some special request orders.

  29. 20-09-2017

    This is the good news, I guess. The output format now can be changed from Windows control panel, and it can be done as firmware update. Once changed this way, the firmware can be also reverted back to its original state. Most typical migrations files are already in the download area.

  30. 06-10-2017

    And, the other good news, which I already posted into the previous (2016) USB module topic, is that Windows 10 now supports USB Audio Class 2.0. It practically means that this device is now plug and play, and basically you don’t need to install any driver.

    And, as far as I can see, this now native Windows driver mostly works well, and sound is good too, even though I think that I still prefer the old dedicated driver version 1.26.

    As for this USB interface series two project, at this moment all the modules, including those with special requests, are practically shipped. There is a couple of exceptions though, because we missed replies from some of you – so if you are reading this, please check your spam folders.

    Completed units are being done too. Their output stage required more checks, but in about ten days we will start shipping them too.

    Thanks for your patience, everyone.

  31. 07-10-2017

    So, for now I can confirm that I like the sound of dedicated driver more, mostly because it is less sibilant (it is not only, and not even mostly about voices – it also lets piano sing more beautify), but this applies to 1.26 version only, and ASIO output. Windows driver is however also quite transparent, and when it comes to Windows stream, I found myself preferring it in some domains.

    I will not proceed with this topic here though, as I plan to start dedicated page, and discuss all those aspects of PC playback that we can hear to affect subjective performance, even though we still can not explain the reasons behind.

    Still, for the reference, this is how this device shows in Windows, with Windows driver. (Click on the picture to enlarge.)



    Windows driver misses some options you have with dedicated driver, but if you want just to connect the device, and forget the rest, this is the way to go. Also, when connecting this device to PC for the first time, it is certainly easier to start this way, and you can try dedicated driver any time later. Apart from bringing own control panel, dedicated driver will make Windows playback device look like this.



    Instruction manual will be updated to reflect the news.

  32. 16-10-2017

    Hello Pedja,

    Thanks for this information. At that point, one have to test as well some simple solution made from FREE Linux distro which their USB free mess.

    For instance free Daphile is based on AudioLinux but run on Ram only avoiding too much processor cunsumption (hence noise)and IS for Windows PC (so no Linux Geek knowledge) for streaming trough USB. Need just 1 Go ram minimum, 2 is better to play in digital domain with the little equalizer embeded (AudioLinux distro origin yet)

    (you can play by disable or not also HDaudio option in the bios of the PC = disable or not UAC2 for further experiments?)

    I play myself through a Archlinux based distro (basicly the same than AudioLinux, Daphile, asf) through the USB on a Synology NAS (cheap : i advise ethe excellent Synology 116 model with its 1 Go of ram. It’s Linux but ask zero Linux knowledge : all is plug & play)

    Goal is of course once again to get rid of USB driver & also to avoid powerfull PC to reduce coupling noise through the USB data bus than a Huge PC is providing even more.

    But all those stuffs has SMPS powersupplies (as the big PC) and if you can isolate ground noise with chip nowadays you can not isolate the noise in the band pass of the streamed packets to the DAC(my low understanding sorry if I’m wrong here, one will correct this in that case). This is imho the origin of good sounding of SD Card reader for instance.

    But in the case of a low powered NAS, one can change the external SMPS (as for laptop)by a linear low noise power supply for the NAS as what is made for the USB to Simultaenous board. But this is certainly an other topic than USB drivers use ! As also the one to isolate from the Internet provider box noise its streaming solution from the noise too…

    And the subject about ABX tests from streaming from Windows 10 since this major update VS Mac/Linux becomes a very interresting one now. Good news, things become easier and the differences between Windows and Linux even smaller.


  33. 19-10-2017

    Hi Pedja:

    1) I sent an email at but no reply.

    2) I wish to order one board; how to order?


  34. 23-11-2017

    Hi Pedja,

    just wanted to ask you when the usb-simultaneous-converter will be ready.
    Will you ship before X-mas or in the next year?
    No hurry, just want to know.


  35. 26-11-2017

    Hello Tobias,

    And firstly thanks for your patience and kindness. There are a couple of completed devices that are still not sent, but it is planned to be done in the next few days. That way your sample will arrive before the holidays, but please let me know if we should postpone shipping.

    Also, the information for anyone who might be still interested in this device / module: the quantity that was made is sold out. And I am not sure if we will make another series. I personally really like this interface, so it is not impossible, but it is no promise, either.


  36. 27-12-2017

    So, here is the idea for Mk3. Eight channels. We need to know if there is enough interest in it.

  37. 18-04-2019

    When will the board be available again?

    Johan Maessen

  38. 03-05-2019

    I am sorry, but we have no such plans at this time.

  39. 18-10-2020

    Hello Pedja,

    I was wondering… I moved recently to a windows 10 pc, using the 1.26 driver and Foobar. On my older machine (XP) that was ‘deeply’ configured for audio, I had completely bypassed the windows mixer. I noticed on the Win10 that the windows mixer is not bypassed, even when selecting ASIO: Audial ASIO (or direct streaming or kernel streaming) => is that normal?
    On the other hand, no windows sounds or other applications are mixed in… which is how it should be.


  40. 19-10-2020

    Hello Berny,

    Only a master volume should be functional (ASIO will not bypass this one), but no other Windows mixer sliders should work. And master volume should be left at max, of course.

    IIRC, it was the same in Windows XP and 7.


  41. 18-06-2021

    How do I use an Audial USB to i2S board to feed 4 TDA1541 chips with R+, R-, L+ and L- to each chip? Is that even useful / better than having / using the chips in parallel?

  42. 18-06-2021

    I generally do not admire parts paralleling. Moreover, with TDA1541A it makes the layout overly complicated.

    For balanced topology, I’d recommend using one TDA for R+ and R-, and the other one for L+ and L-.

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