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ζ1 - AMB's implementation of the Audio Widget USB-I²S

zeta1 - AMB's implementation of the Audio Widget

ζ1 - AMB's implementation of the Audio Widget USB-I²S

Postby amb » August 8th, 2014, 2:11 am

ζ1 - the Audio Widget

The ζ1 ("zeta 1") is the USB-I2S transceiver module that will be used in the upcoming γ1.5 and γ3 DACs. It may also be used in other future projects. This module is AMB's implementation of the open source "Audio Widget" project.

Audio Widget supports asynchronous (rate-feedback) USB audio in two modes (switch selectable), in up to 32 bits depth:
UAC1 mode: All standard sample rates between 44.1K and 48K inclusive.
UAC2 mode: All standard sample rates between 44.1K and 192K inclusive.

UAC1 is plug-and-play on all platforms with no special device driver needed.
UAC2 is plug-and-play on Linux and MacOS with no special driver needed. On Windows, an ASIO driver is available to support UAC2 mode.

The heart of the Audio Widget is the AT32UC3A3256 32-bit microcontroller from Atmel. It's a large 144-pin device in a LQFP package. The open-source Audio WIdget firmware runs on this controller, and the firmware can be flashed via the USB port. Currently the only output format is PCM (Philips I2S). I hope to implement support for DSD audio some time down the line.

I began work to lay out the ζ1 PCB. It is based on Børge Strand-Bergesen's work of Henry Audio, formerly QNKTC), and will be pin-compatible with his version. His current USB-I2S module has two sets of interface pin/socket connectors to the main board, one is 2mm pitch, and the other is 2.54mm pitch. The older version of his USB-I2S only had the 2mm pitch holes, and his analog board uses only the 2mm pitch holes. In the interest of keeping the PCB as small as possible, I chose to omit the 2.54mm pitch holes from my version, so dimensionally it will be the same as Børge's old USB-I2S module at 67mm x 42mm. I also kept the USB connector at the same location for compatibility.

I am doing this at the same time as working on the γ1.5 and γ3 DACs. The ζ1 can be an independently-developed and tested piece just like the α24. Prototype ζ1 boards could be tested on the γ1.5 DAC as well as on the Børge's analog board. This is the beauty of modularity and pin-compatibility.

Even though this is essentially duplicating an existing design, it's by no means easy. All I have is a schematic diagram, a dimensional drawing, and an actual module. The schematic does not identify some important parts (such as the brand and model of USB connector, small SMD pushbutton switches, and a few other things), so it takes a lot of effort to research this and select parts that are available and fit the board well. I then have to create new Eagle library parts for each of these. This work is now all done.

Why re-invent the wheel?

I originally thought that γ1.5 and γ3 builders could simply buy USB-I2S modules directly from Børge, but he does not currently offer just the module. You must buy his entire DAC. Also, in my previous email conversations with him, he indicated that this would make unpredictable demands on his stock and make it difficult for him to schedule board runs (in terms of time and quantity). He currently ships exactly one USB-I2S module per DAC, so it's easy to handle.

I then considered sourcing special production runs of the modules "in bulk" from Børge and reselling them at AMB audio shop. But this also has its own set of issues.

Finally, I decided to implement my own version for the following reasons:

- It gives me complete control over supply, quantity, pricing and stocking issues.
- It shields Børge from all of the above, so it does not impact his operation.
- It shields us from problems if Børge decides to stop making modules, or if he makes incompatible changes to it in the future.
- It allows me to directly make enhancements to the design if such opportunity comes up.
- It avoids support problems: Børge need not provide community support for my version, and vice versa.
- It should result in cost reduction due to less overhead.
- It could be ordered from AMB audio shop at the same time as the other γ1.5 and γ3 items (including the main board, DAC board and α24).
- It could be an item that builders use to implement their own high resolution DACs.
- It allows me to more easily design other future projects around it.

The downside of this. is that I will not only have to create the new version of the Audio Widget, but also tie a significant sum of money in inventory. These are not like the small chips or parts that AMB audio shop currently offers. But I am willing to do this for our community.

AMB's ζ1 Audio Widget will identify itself with a different USB VID/PID than Børge's version, or any other Audio Widget implementations. This means that the ζ1 will be running its own version of the firmware (based on the main Audio Widget git repository). It should be plug-and-play on Linux and MacOS, and I have added support for the AMB VID/PIDs in the current Windows driver git repository.

The fact that Audio Widget is truly open source (open hardware, open firmware, open driver) allows this to happen, which is one of the reasons why I selected the Audio Widget design in the first place. Perhaps the most important reason.

Of course, Børge deserves full acknowledgement and credit for his work (as well as the rest of the Audio Widget team). Without which this project wouldn't be possible. Credit should also go to George Boudreau, the Audio-Widget project, and the SDR-Widget project that spawned it.

Current version
(version 1.0, updated 23 December 2014)

A lot of work has occurred since the introduction. Boards have been assembled and tested by members of the prototype team. It has been verified that the ζ1 is functioning correctly with the γ1.5 portable DAC + headphone amp. I also performed extensive bench testiing with excellent results. Production assembled modules are now available. Please refer to the official ζ1 website for the latest information.

Here are the latest schematic diagram, PCB layout, 3D rendering and BOM.

Schematic diagram:
Image
Image

Overview (all layers):
Image

Top layer + top silkscreen:
Image

Top layer:
Image

Inner layer 1:
Image

Inner layer 2:
Image

Bottom layer:
Image

3D rendering:
Image

Photo of assembled board:
Image

BOM:
NOTE: The production ζ1 will come as a pre-assembled and tested module. The only additional parts you need to order for the ζ1 are the items shown in bold font below, as they will not be supplied with the module.

qty | id | desc | vendor part number (M) = Mouser, (D) = Digi-Key
------------------------------------------------------------------------------
0 | R1 | not populated | -
3 | R2,R11,R12 | 4K7 resistor 0603 SMT | (M) 660-RK73H1JTTD4701F; (D) RMCF0603FT4K70CT-ND
2 | R3,R4 | 39R resistor 0603 SMT | (M) 660-RK73H1JTTD39R0F; (D) RMCF0603FT39R2CT-ND
2 | R5,R6 | 10K resistor 0603 SMT | (M) 660-RK73H1JTTD1002F; (D) RMCF0603FT10K0CT-ND
1 | R7 | 6K81 resistor 0603 SMT | (M) 660-RK73H1JTTD6801F; (D) RMCF0603FT6K81CT-ND
1 | R8 | 1M resistor 0603 SMT | (M) 660-RK73H1JTTD1004F; (D) RMCF0603FT1M00CT-ND
2 | R9,R10 | 1K5 resistor 0603 SMT | (M) 660-RK73H1JTTD1501F; (D) RMCF0603FT1K50CT-ND
1 | R13 | 0R jumper 0603 SMT | (M) 667-ERJ-3GEY0R00V; (D) P0.0GTR-ND

2 | C1,C5 | 10n capacitor 0603 SMT | (M) 81-GRM1885C1H103JA1D; (D) 490-9666-1-ND
15 | C2-C4,C6,C7,C15-C24 | 100n capacitor 0603 SMT | (M) 81-GRM39X104K25; (D) 490-1524-1-ND
1 | C8 | 10p capacitor 0603 SMT | (M) 81-GRM39C100B50D; (D) 490-9713-1-ND
2 | C9,C10 | 22p capacitor 0603 SMT | (M) 81-GRM1885C2A220JA01; (D) 490-1335-1-ND
1 | C11 | 470p capacitor 0603 SMT | (M) 81-GRM39C471J50; (D) 490-1443-1-ND
1 | C12 | 2u2 capacitor 0805 SMT | (M) 810-C2012X7R1C225K; (D) 445-1420-1-ND
1 | C13 | 4u7 capacitor 0805 SMT | (M) 810-C2012X7R1C475K; (D) 445-6859-1-ND
1 | C14 | 1n capacitor 0603 SMT | (M) 81-GRM1885C1H102JA1J; (D) 490-6379-1-ND

2 | L1,L2 | Taiyo Yuden BKP1608HS101-T ferrite bead | (M) 963-BKP1608HS101-T; (D) 587-1922-1-ND
2 | E1,E2 | Littelfuse PGB1010603MR transient absorber | (M) 576-PGB1010603MR; (D) F2594CT-ND

1 | U1 | SN74LVC2G157DCUR 2-1 selector multiplexer | (M) 595-SN74LVC2G157DCUR; (D) 296-12605-1-ND
1 | U2 | Texas Instruments TPS73633DCQR voltage regulator | (M) 595-TPS73633DCQR; (D) 296-16914-1-ND
1 | U3 | Atmel AT32UC3A3256 LQFP144 microcontroller | (M) 556-AT32UC3A3256ALUT; (D) AT32UC3A3256-ALUT-ND
1 | X1 | 12MHz 18pF 50R ESR crystal 5x3.2mm 2-pad SMT | (M) 774-445I23D12M00000; (D) CTX1170CT-ND
1 | D1 | Comchip CDSU101A diode | (M) 750-CDSU101A; (D) 641-1002-1-ND
1 | LED1 | LED (red) 1206 SMT | (M) 606-CMD15-21VRD; (D) L62301CT-ND
1 | LED2 | LED (grn) 1206 SMT | (M) 606-CMD15-21VGD/TR8; (D) L62305CT-ND

0 | J1 (do not install in normal builds) | 10P dual-row header SMT | (M) 571-5-146130-4; (D) A115293-ND
1 | J2 | Hirose UX60SC-MB-5ST USB Mini-B connector | (M) 798-UX60SC-MB-5ST80; (D) H11671CT-ND
2 | SW1,SW2 | SPST-NO tactile switch SMT | (M) 506-FSMSM; (D) 450-1140-ND

1 | 25P pin receptacle strip 2mm pitch (*) | (D) S5751-25-ND
1 | 6P pin receptacle strip 2mm pitch (*) | (D) S5751-06-ND
3 | 15P pin receptacle strip 2mm pitch (*) | (D) S5751-15-ND


1 | PCB | (A) AMB zeta1 PCB
------------------------------------------------------------------------
(*) - use the 25P + 6P strips for board connector pins 0-30, use two 15P strips for pins 31 - 60, and one 15P strip for pins 61-75.
- The mating pin headers are Digi-Key S5800-xx-ND, available in all 01-40 pin sizes.
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby LV26 » August 8th, 2014, 3:55 am

The schematic does not identify some important parts (such as the brand and model of USB connector, small SMD pushbutton switches, and a few other things), so it takes a lot of effort to research this and select parts that are available and fit the board well.


Hello,
If you need some assistance I would be glad to help you.
But I`m in vacation. I can start after August, 18.

-- Regards,
Victor
Everything should be made as simple as possible, but not simpler. // Albert Einstein
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby DEFL » August 8th, 2014, 3:58 am

And here comes AMB product with massive SMD work. Which is totally different philosophy from through hole world (technique, soldering and desoldering tools, various tweezers, oven with regulated temperature, solder paste etc) :)
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby amb » August 8th, 2014, 4:06 am

LV26 wrote:...
If you need some assistance I would be glad to help you.

Thanks LV26, I have already completed that part of the work. I've been busy with this, along with many other things! :)

DEFL wrote:And here comes AMB product with massive SMD work. Which is totally different philosophy from through hole world (technique, soldering and desoldering tools, various tweezers, oven with regulated temperature, solder paste etc) :)

Yes, but I will offer it as a pre-assembled module. Asking people to hand-solder a LQFP144 package is courting failure!

I should also mention that this board will probably push some boundaries in terms of via hole sizes, trace widths, distance between traces and board edges, clearances, etc. I will have to contact my PCB fab to make sure I am designing within their capabilities.
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby cobretti » August 8th, 2014, 12:16 pm

DEFL wrote:And here comes AMB product with massive SMD work. Which is totally different philosophy from through hole world (technique, soldering and desoldering tools, various tweezers, oven with regulated temperature, solder paste etc) :)

No worries. Flood the LQFP144 with solder and then use a solder wick. That's fastest and easiest approach. ;)
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby amb » August 8th, 2014, 12:40 pm

cobretti wrote:No worries. Flood the LQFP144 with solder and then use a solder wick. That's fastest and easiest approach. ;)

... Until solder gets behind the pins and cannot be wicked out, or if your wick gets stuck, requiring enormous amount of heat to unstick -- which could damage the part and/or board.
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby MisterX » August 8th, 2014, 12:48 pm

Yeah, solder paste + hot air is much easier but you can run into problems with whiskers behind the pins.
1352.5 and counting.
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby cobretti » August 8th, 2014, 12:53 pm

amb wrote:
cobretti wrote:No worries. Flood the LQFP144 with solder and then use a solder wick. That's fastest and easiest approach. ;)

... Until solder gets behind the pins and cannot be wicked out, or if your wick gets stuck, requiring enormous amount of heat to unstick -- which could damage the part and/or board.


That never happened to me. Make sure the solder pads are the proper length.
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby mikeg88 » August 11th, 2014, 2:17 pm

amb wrote:Even though this is essentially duplicating an existing design, it's by no means easy. All I have is a schematic diagram, a dimensional drawing, and an actual module. The schematic does not identify some important parts (such as the brand and model of USB connector, small SMD pushbutton switches, and a few other things), so it takes a lot of effort to research this and select parts that are available and fit the board well. I then have to create new Eagle library parts for each of these

If you want help with picking parts or anything else, I'm happy to help, PM me if needed.

amb wrote:The downside of this. is that I will not only have to create the new version of the Audio Widget, but also tie a significant sum of money in inventory. These are not like the small chips or parts that AMB audio shop currently offers. But I am willing to do this for our community

You're awesome, AMB! Thank you, once again, for your relentless commitment to the community.

amb wrote:Image

...can you post a mechanical drawing of this? (board dimensions, pin positions, and USB connector position) Or alternatively, just give a link to the drawing provided by Børge?
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Re: ζ1 - AMB's implementation of the Audio Widget USB-I2S

Postby linux-works » August 11th, 2014, 7:34 pm

just go onto diyaudio and search for 'audio widget' and you'll find huge threads that talk about this SoC board.
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