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Open-source USB interface: Audio Widget
Open-source USB interface: Audio Widget
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Old 26th December 2011, 01:45 PM   #651
borges is offline borges  Norway
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Hi Alex,

sorry for the double posting... But the only way to test the bumper-to-bumper stuff is to scope the data line at word clock transitions. With known data (for example all 4 least significant bit being the same, and different from the MSBs) it is easy to see.

But to listen for a properly conveyed 32-bit LSB may be a bit tricky :-)

BÝrge
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Old 26th December 2011, 02:20 PM   #652
alexlee188 is offline alexlee188  Canada
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HI Borge,

Please do the scope test to confirm that indeed the I2S has the correct 32bit data :-) It will be harder to test whether the DAC can interpret the last few bits of the 32 bit data though.

As far as I'm concerned, if I can't hear the difference, it makes no difference :-)

Alex
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Old 26th December 2011, 02:37 PM   #653
wlowes is offline wlowes  Canada
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Default Great advice

Quote:
Originally Posted by UnixMan View Post
probably the easiest way to begin playing with Linux would be to ...
Thanks UnixMan. This is exactly the kind of advice I was looking for. I will likely take this one step at a time, but I must admit, the dedicated appliance is where I would like to land. The concept is elegant in its simplicity. There is no extraneous hardware or software at the player. Also, I love the simplicity of the linear power supply, and the isolation from all the hdd/monitor etc.
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Old 26th December 2011, 02:49 PM   #654
Turbon is offline Turbon  Sweden
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Quote:
Originally Posted by wlowes View Post
Thanks UnixMan. This is exactly the kind of advice I was looking for. I will likely take this one step at a time, but I must admit, the dedicated appliance is where I would like to land. The concept is elegant in its simplicity. There is no extraneous hardware or software at the player. Also, I love the simplicity of the linear power supply, and the isolation from all the hdd/monitor etc.
Yes, a dedicated machine will my next step as well but for now I chose the fat lady - Fedora 16 KDE on an old laptop. Imagine that wireless worked right out of the iso file! Now I need some lightweight no fuss players.

Brgds
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Old 26th December 2011, 05:17 PM   #655
oneoclock is offline oneoclock  Europe
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Greetings.
I received the sdr-widget AB-1.1 DAC. Great sound.

I would try external source to clock and DAC. Where is some information to make an external source for the AB-1.1?

I have doubts about the operation.

- J2: 3.3 V. --> VDD_SENSE VBUS_EN (off). (Then ADP151AUJZ_3.3 regulators OFF.)
Can be applied:
- J3: 3.3 V. 75 mA VDD_XO.
- J4: 3.3 V. 30 mA for analog DAC AVCC.
Would this be aproximately correct to begin?
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Old 26th December 2011, 08:17 PM   #656
UnixMan is offline UnixMan  Italy
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Originally Posted by alexlee188 View Post
So now it is up to the DAC to interpret the 32 bits coming in through the I2S bus

I have just tested it with my AB1 and it sounds exactly the same as the old firmware (which is expected).
given that IIRC ES9023 is only a "24 bit" DAC, I guess it doesn't matter whether the 8LSB are truncated by the uC or by the DAC...
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Old 26th December 2011, 08:31 PM   #657
UnixMan is offline UnixMan  Italy
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Quote:
Originally Posted by Turbon View Post
Now I need some lightweight no fuss players.
If you use KDE, the natural choice would be "AmaroK"... but I'm afraid that doesn't exactly match your "lightweight no fuss" specs.

For a desktop based stand-alone player that match your requests you may want to have a look at gogglesmm (Goggles Music Manager).
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Last edited by UnixMan; 26th December 2011 at 08:34 PM.
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Old 26th December 2011, 08:37 PM   #658
rsdio is offline rsdio  United States
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Originally Posted by UnixMan View Post
I was just wondering what does this mean in practice WRT 24 vs. 32 bit. Isn't data always sent encoded in 32bits over the USB?
At the highest level, USB is always 8-bit data. All data formats are expressed as collections of 8-bit bytes. Within the USB Audio Class, audio is sent as 8-, 16-, 24-, or 32-bit samples. A separate parameter specifies how many bits are valid, allowing 12-bit and 20-bit or other rare formats. The clock rate for USB data is fixed by the host, which is why UAC asynchronous uses rate feedback to control the effective sample rate.

Note that if you are running into USB bandwidth issues, then it might make sense to change from 32-bit samples to 24-bit samples, especially if your source data is only 24-bit anyway. Using 32-bit samples over USB just takes 33% more bandwidth with no benefit other than the fact that it's the same format when you do have 32-bit source material.

The I2S is completely independent of the USB format, with the obvious exception that the overall bandwidth cannot be exceeded. I2S is truly serial, with no requirement that the bit count be a multiple of 8. I2S Master and Slave can even use a different number of bits, with the understanding that the Word Clock will select the Most Significant Bit and any extraneous or missing bits will fall at the end of each word. The critical aspect is to align the MSB, although you might not be able to tell that it's off by one unless you have careful test data.

The bit clock rate of I2S determines the maximum sample rate, combined with the bit depth. If you have a low bit clock rate and a large sample bit depth such as 32-bit, then your maximum sample rate will be lower than if the bit depth were dropped to 24-bit. Using a higher bit clock rate allows the bit depth to be 32-bit without hitting any limits. Basically, the difference between the bit clock rate divided by the bit depth and the sample rate determines how many 'empty' bits there are between words on the I2S. At high sample rates, there may be 0 'empty' bits between words, and that's what people are concerned about. Different hardware will have different success at these extremes. Some serial peripherals will have no problem with back-to-back sample bits, while others will be flaky. Since the Audio Widget is fixed, and folks here have already reported success, then the only problem might be the DAC at the receiving end. Also, if future Audio Widget change the hardware for the I2S Master, then there might be opportunity for problems at the extreme.
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Old 26th December 2011, 09:18 PM   #659
Turbon is offline Turbon  Sweden
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Quote:
Originally Posted by UnixMan View Post
If you use KDE, the natural choice would be "AmaroK"... but I'm afraid that doesn't exactly match your "lightweight no fuss" specs.

For a desktop based stand-alone player that match your requests you may want to have a look at gogglesmm (Goggles Music Manager).
Nah, amarok was about the first to be removed. Well, gogglesmm seemed to follow the rest of the pack with willingness to organize my media and so forth... I like vlc even though it isn't really lightweight. I would like something as pureplayer for linux that gives a sh*t about my media! It should really just ask what file or library do you want to play... Easy as that or can I just pipe a file to the device? In that case I can write my own script to use.

Brgds

Sorry folks, a bit OT... But still destilling what I need to check the AW out with my terms...
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Old 27th December 2011, 12:09 AM   #660
UnixMan is offline UnixMan  Italy
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Originally Posted by Turbon View Post
Well, gogglesmm seemed to follow the rest of the pack with willingness to organize my media and so forth...
no, not necessarily.

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Originally Posted by Turbon View Post
It should really just ask what file or library do you want to play... Easy as that or can I just pipe a file to the device? In that case I can write my own script to use.
oh... than you came to my own favourite "player":

Code:
 AUDIODEV=hw:1,0 play *.flac
The command "play" is just a different name for "sox". Install sox and all of its plugins and you're done.

(setting the "AUDIODEV" env. variable is only needed if you want to output to a device different from the default one).
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