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Old 24th December 2011, 09:30 PM   #621
deandob is offline deandob  Australia
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Turbon,

Most of what you need can be found on MSDN and similar online resources, like the links below.
http://social.msdn.microsoft.com/For...opment/threads
FreeLists / WDMAUDIODEV

If you are game to tackle this (and its going to be hard if you are not a C++ Windows system developer) I recommend starting with the MSVAD virtual audio device sample in MSDN, all the DDK work is done for you, you can extract the audio data from the source application from the COPYFROM buffers and pipe it through your USB code.

I posted a bit of this information in the audio widget group last month, please check that thread - but I gave up on developing a UAC2 driver due to the work involved (as others have noted). I think there will be a number of UAC2 solutions coming out over the next 6 months but unfortunately not from Microsoft (it is not planned for Windows 8 at least from looking at the early releases) due to lack of demand. These third party solution (eg. CMedia) will have their own drivers tied to their hardware so it will probably not be possible to hack them in the DIY world.

I am going a separate route now, I will develop a custom driver based on the MSVAD sample and the Cypress CY7C68013A USB High Speed chip which has its own transport from the PC side to the chip (ie. no significant USB code to write!). The driver I'll implement will not be standards based, but then again for Windows you either have to purchase a 3rd party UAC2 driver or have a proprietary approach. I have discussed the pros/cons of this approach with Koon in his thread on a async USB High Speed I2S solution and he has a prototype working using a different chipset (its actually ending up to be a fairly simple solution).

Good luck & Happy Holidays!
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Old 24th December 2011, 10:19 PM   #622
Turbon is offline Turbon  Sweden
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Thanks for the support deandob! One of my strenghts is that I don't know when to stop. I am not to write the whole code but hopefully there will be those who will do it with people like me testing and scrutinizing their work. I might even write parts myself (good forbid) but the parts will be fully open to anyone to a view and comment on or show a better way. I do confess that writing low level windows system programs arn't something I have been doing since windows was young. The start and the easy part is to write a framework with what we know and if anyone is interessted comment more than less in the code assuming that people doesn't understand what the lines are doing. Personally I hate documenting...

The effort will be wholly community driven so people are invited to add as long as they want to - as soon as the code is checked in the ownership is transferred to the proper group - which I'm not totally aware of at this time. I know there is a group but I have seen no manifests yet. But the legal framework is easy to set up - I have some close contacts with people living on the subject so continue or start a new one is no problem - whichever as long as the code will be free to alter, use and even sell as long as the credits goes to the free project.

Brgds
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Old 24th December 2011, 10:53 PM   #623
Turbon is offline Turbon  Sweden
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deandob.

Please let me know when your implementation is ready and I'll be in for a kit or in whatever form you decide to release it in.

Brgds and happy holidays for you to.
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Old 25th December 2011, 12:36 AM   #624
rsdio is offline rsdio  United States
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Quote:
Originally Posted by BÝrges View Post
Please follow the link from my signature and look at the module schematics. L1006 and L1007 are between USB VBUS/GND and those on the board.

The components are 0603. If you suggest any alternative components, please let me know! The ones used I copied from an unrelated USB design.

Oh, and if the sch/layout could be improved on, let us know about that too.
Last time I looked was the June 28 schematic, and I had not seen the USB module yet. I'm now looking at the July 3 USB module schematic...

I see that you have L1006 between the CHASSIS pins on the USB mini-B connector and the board GND, but that is not the correct placement. L1006 should be placed between the GND pin on the USB mini-B and the board GND. Remember that power flows in a circuit, so you should place the beads identically on the +5V and GND pins.

Meanwhile, the two CHASSIS pins should not be directly connected to ground because this will conduct shield noise into the board ground. Instead, create a high impedance filter with a 1 MΩ resistor and 0.1 uF capacitor in parallel.

Search for dsk5509a_Schematic.pdf and refer to sheet 13 of 17. This is a TMS320 DSP evaluation kit board schematic from Spectrum Digital that is available on their web site. The only thing I added that is not shown in the SD schematic is a cap across VUSB and GND that is ahead of the beads and corresponds roughly to your C1075 (assuming you break the CHASSIS ground away from the power GND).

EVM5509A Plus Support Home

P.S. My apologies for not noticing that you were already using beads. When someone suggested that you should always use a USB cable with ferrite beads, I immediately assumed that you did not have any filtering on your board. I think that if you move the bead on the ground then your board will work equally well with all USB cables.

Last edited by rsdio; 25th December 2011 at 12:39 AM.
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Old 25th December 2011, 01:42 AM   #625
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Quote:
Originally Posted by Turbon View Post
I believe Alex played with the caps according to some older posts in the google audio widget group. Fo myself - I haven't even given them a thought since the s
Merry Chritmas and happy holidays to all

We are always happy to see reports on SQ on the analog mods. The major tweaks include using alternative power supplies (bypassing the onboard USB -> ADP151) such as the use of Silas Shunts or LiFePo4 batteries etc., and changes to the various caps.

Please first of all report your board's SQ based on the stock configuration so that we have a baseline. Is the sound better or worse than your previous DAC? In what way?

Now back to the question of caps. We have indeed played with the caps and they make a significant audible difference to the SQ.

First some theoretical discussion. If you know all of these already please skip this section

The caps in use in practice are far from an ideal circuit element. Besides the basic capacitance value, there are other parameters such as the ESR, dielectric loss etc., which affects the performance. What and how caps should be used is also determined by the intended function (eg. whether you are bypassing the chip in question, or you are filtering the supply noise coming from outside the chip, or as a reservoir cap for charge pump etc.) Bypassing digital noise (eg for an XO) has different requirements from "smoothing" the supply for analog opamps etc.

To remove very high frequency noise from the supply line, you would like to use a small capacitance value. This is because the ESR (plus the circuit board reactance) and the capacitance value combined will dictate the resonance frequency - filtering will be most effective near the resonance frequency. So if you use just a high capacitance, such as 100uF, but your ESR is not ultralow, your cap can only deal with relatively low frequency noise and will be ineffective for high frequency noise.

So we have BOTH a low capacitance cap in parallel with a high capacitance cap to deal with both low and high freq noise. Using a 100uF cap may NOT be as effective as a 10uF cap if the noise you want to filter is 50/60Hz rather than 5/6 Hz

However, you cannot simply use any combination, as the two caps in the circuit may cause parasitic oscillations, and the resulting noise may be worse than the supply noise you want to filter in the first place. In general it is a bad idea to use two caps of the same value and type, eg 10uF + 10uF. It is safer to use a very small value in one, and a higher capacitance in the other. Again it depends on the ESR and other characteristics.

So choosing the right caps is a black art

If you look at the older posts in this thread, you will find reports of Wei using Blackgate-N caps to excellent effect. JKenny also reported his tweaks using other caps. I myself use Sanyo OSCONs (as I can't afford the Blackgate-N's). They have also reported the cap values used in various positions.

However, when you change the power supply (say to Silas shunts), the caps may have to be changed as the noise and impedance characteristics are different.

So much tweaking is requried - and that is the whole point of this project. Analog tweaking of the audio-wdigets is part of the fun

Alex
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Old 25th December 2011, 08:31 AM   #626
starn02 is offline starn02  Italy
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I don't know if the previous post applies to my request regarding the charge pump caps .... in any case, what is the default value of cap to be used there? I miss the complete es9023 datasheet, and before experimenting I'd like to avoid mistakes in values that can possibly damage the chip ...
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Old 25th December 2011, 09:48 AM   #627
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You might like to refer to an old post to this thread in this forum. I have reproduced the content below if you are not up to reading old posts :-)

Alex

On Tue, Jun 14, 2011 at 01:26, Alex Lee <alexlee...@gmail.com> wrote:
>> Hi all,
>> Wei (2A3SET) had posted his mods to the USB9023 board to the DIYaudio forum,
>> and the following is a copy & paste of his post:
>> ================================================== ========================= =======================================
>> Audio-widget with UAC2 driver runs pretty good, a big step up from UAC1 with
>> same 16/44.1 material. Very interesting, even with async mode under windows
>> 7 comparison between the minimalist(andy) audio player and foobar player
>> showed minimalist better, it shares same quality of sound with ecasound
>> under ubuntu studio.
>> I just upgraded the capacitors around ES9023 to BlackGate N, first tried the
>> VREG (10u) and Pump capacitor (4.7u) to bring SQ to a higher level with silk
>> smooth sound and quieter background, then the bypass for 3.3V (10u) and -3V
>> (4.7u) of ES9023. The onboard regulator ADP-151 sounds pretty good already,
>> although personally I think it worth a try to replace it with Salas shunt
>> (run as external modules). Anyway I am still pretty happy runing with USB
>> bus power so far.
>> ================================================== ========================= =======================================
>> He has done further mods and tests, with supplying an external clean power
>> supply to the ES9023 and to the Oscillator, with improved sound quality.
>> The SQ obtained has already surpassed Wei's own souped up NOS TDA1541 DAC.
>> He intends to compare the USB9023 with the Acko 9023 DAC in future.
>> We welcome more builders to do mods and report test results. These efforts
>> will help in improving the design of the next versions of audio-widgets.
>> George still has 11 bare boards and parts enough for 3 sets.
>> Borge is planning for the next run of AB-1 and maybe some of these mods can
>> go into the AB-1 as well.
>> Alex
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Old 25th December 2011, 10:10 AM   #628
starn02 is offline starn02  Italy
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I've seen that post and the 4u7 value, but in my board I have 1u ... so I still wonder what's the "normal" value ... and where I can reach
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Old 25th December 2011, 08:46 PM   #629
UnixMan is offline UnixMan  Europe
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Quote:
Originally Posted by borges View Post
Yes, you can latch onto the half-moon pads on the edge of the module. There's no dedicated I2S header. (Hint to self for revised layout...)
also a "digital interface" board with the AW uC complete with on-board clocks (and dividers) plus buffered I2S, MCLK and perhaps S/PDIF outputs would be nice for easy integration with existing DACs!

Happy Holidays to everyone!
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Old 25th December 2011, 08:48 PM   #630
UnixMan is offline UnixMan  Europe
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Quote:
Originally Posted by borges View Post
Bumper-to-bumper I2S can be risky, so 24-bit data to the DACs is preferable.
what do you mean?
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