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Open-source USB interface: Audio Widget
Open-source USB interface: Audio Widget
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Old 25th December 2011, 11:28 PM   #641
UnixMan is offline UnixMan  Italy
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Originally Posted by wlowes View Post
What would you recommend as a first experiment in Unix for USB2 music from a laptop. This can be a dedicated machine with no other use than playing music in its finest form.
probably the easiest way to begin playing with Linux would be to install a full distribution such as "Ubuntu" (perhaps the "Ubuntu Studio" variant). But, for a dedicated "music machine", IMHO the best thing to do is to use a dedicated system already optimized for audio, such as Voyage MPD.

For the easiest doployment of Voyage MPD you'll need a LAN with a small router (providing DHCP) connected via Ethernet to the machine that will act as "music server" (WiFi configurations are possible too, but a bit more complex to set-up).

After configuration, the "music server" (the machine connected to the audio system) wil run as an appliance without the need for a local user interface (not even a display).

It will be remotely controlled from user interface(s) running on other machines/devices (even including hand-helds), namely MPD clients.

Among these, for use on a computer (another laptop/netbook or a desktop, with either Linux, Windows or MacOS/X), I'd recommend the nice, easy and featurefull "GMPC".
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Last edited by UnixMan; 25th December 2011 at 11:43 PM.
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Old 25th December 2011, 11:31 PM   #642
Turbon is offline Turbon  Sweden
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Originally Posted by UnixMan View Post
Tried some small mods on my AB1.1:

added C15, C21 and C31: 100uF

added C34: 47uF, OsCon

added C26 in parallel to C32: 470uF

added C27 in parallel to C33: 47uF, Elna Cerafine

added C29 in parallel to C35: 47uF, Elna Cerafine

www.audiofaidate.org • View topic - Async USB2 - SDR/Audio-Widget collaborative project
Did it improve sound?

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Old 25th December 2011, 11:37 PM   #643
UnixMan is offline UnixMan  Italy
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Originally Posted by 1audio View Post
I found the output low pass filter was important, at least with wide band electronics following. The uhf stuff at the output is significant.
what values have you used for R and C?

(I like the possibility to directly drive my hearphones too, thus the R must be kept very small. I guess no more than a few ohm. What about f3? 40KHz could be ok?).
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Old 25th December 2011, 11:42 PM   #644
UnixMan is offline UnixMan  Italy
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Did it improve sound?
I'm still unsure about that...

There seems to be some, but overall I have mixed feelings. I'll let you know when I'll have some more definitive conclusions.
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Old 25th December 2011, 11:50 PM   #645
merlin2069er is offline merlin2069er  Canada
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Is there any way to get a digital output (spif) from this audio widget?

I'm looking for a usb front end for my ezdac.
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Old 26th December 2011, 04:55 AM   #646
1audio is offline 1audio  United States
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Open-source USB interface: Audio Widget
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Originally Posted by UnixMan View Post
what values have you used for R and C?

(I like the possibility to directly drive my hearphones too, thus the R must be kept very small. I guess no more than a few ohm. What about f3? 40KHz could be ok?).
My notes are here: http://www.diyaudio.com/forums/digit...ml#post2747950

I have not dug further into the limits but you may be hitting a brick wall with the ESS9023. The part meets or exceeds its published specs in this system. It does have some odd issues, overload is a specific one with the datasheet talking about a resistor (R15) affecting its clipping performance. It seems R15 sets the Vref for the DAC so its value and the optimized grounding of the associated caps will be critical. Keeping the digital and analog grounds isolated is challenging in a small device like this, especially when the analog power is derived from the digital side and there is no practical way to fully isolate the USB system from the DAC. This said I believe really close study of the PCB and its power and ground for the analog system, possibly even disconnecting all the analog ground connections and using a star ground (wirewrap wire would be OK on this side) could make a big difference in the final sound.

The spec sheet calls out the 4n7 caps on the output, and it also says the load must be higher than 10K (at least for the spec measurement) (no headphones here). The Nuforce U-dac that uses the same DAC chip uses a TI TPA4411 output amp, which helps a lot.

Its clear that the chip could benefit from some very careful supply and grounding help. However my experience suggests looking at the AKM4430 http://akm.lfchosting.com/datasheets/ak4430_f01e.pdf may get a better sound in this application (and possibly cheaper). Its only 16 pins and has a charge pump. The pinout is enough different that its not a drop-in.
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Old 26th December 2011, 05:03 AM   #647
1audio is offline 1audio  United States
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Originally Posted by merlin2069er View Post
Is there any way to get a digital output (spif) from this audio widget?

I'm looking for a usb front end for my ezdac.
You could add an I2S to SPDIF chip.
AK4104, DIT4192, CS8406 and others. I think the AKM datasheet suggested that its autodetect for everything but I didn't read it.
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Old 26th December 2011, 10:44 AM   #648
UnixMan is offline UnixMan  Italy
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Originally Posted by 1audio View Post
d that I was happy with:
1) 25 uF cap in C34
mmmh, may be I went a bit too far on this one with 47uF? I'll try with smaller values too.

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2) 470 uF 25V caps in C21 and C31
makes sense... unfortunately I did not have suitable parts at hand. Maybe I should get and try those Panasonic. Indeed, having the cap after the v.reg. larger than the one before it is something I didn't quite like. OTOH, I wanted to have small Xc @ low freq (and plenty of stored energy) as close to the analog circuit as possible. I don't quite like the idea of audio signals circuit closing through a voltage regulator. I definitely prefer it to close (as much as possible...) through just a capacitor. Non-ideal as it can be, yet better than the complex active circuitry of any voltage regulator.

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Originally Posted by 1audio View Post
These Panasonic parts
http://www.mouser.com/ProductDetail/...71L/?qs=y8NZ%2...
seem to work really well.
Oh, BTW: the link does not work! Could you please provide a correct one?

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Originally Posted by 1audio View Post
3) 6.8 nF polystyrene caps at C251 and C253
so you just added the caps, without replacing the 0R with a true resistor (or inductor)?

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Originally Posted by 1audio View Post
4) Ferrite donut on the USB cable.
sure, me too.

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I'm looking forward to the future variants of this technology.
yup... it's time to gettin' serious, with a fully self-powered and fully dual-mono unit based on a couple of top-end DAC chips. Possibly also with optoisolators between uC and AB.

The AB1.1 is nice and sounds quite well, but it's still far from the SQ of my current setup.

Especially for what regards sound "richness" and "imaging". With my reference setup the latter in particular is kind of magic. Virtual image usually extends well over the limits of the speaker positions: (with some recordings) it may get close to a 180° sound stage, extending almost to the sides of the listening position! While still being perfectly stable, properly sized and focused (no, I don't use ambiophonics or any other sound processing).

On the contrary (all the rest being the same) with AB1.1 the image is always enclosed in the space within the speakers. (and it's also somewhat less stable/clear/defined than my reference).
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Last edited by UnixMan; 26th December 2011 at 10:54 AM.
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Old 26th December 2011, 11:09 AM   #649
borges is offline borges  Norway
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Oh, BTW: the link does not work! Could you please provide a correct one?
Try Capacitors | Aluminum | Digi-Key

Børge
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Old 26th December 2011, 01:03 PM   #650
alexlee188 is offline alexlee188  Canada
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Originally Posted by borges View Post
Over USB it can be various formats. As long as we're using at least as many bits as the source material, we can zero pad all we want. Obviously, the used bandwidth must be within specs.

I may need some input from Nikolay and Alex on this one, but I believe we're transmitting 24-bit audio using 32-bit USB words and 24-bit DAC words.

The DAC uses 64 I2S ticks for 24+24 data bits. If it used the same 64 bits for 32+32 bits we'd have to confirm its bumper-to-bumper-ness. But at 24+24 the dead bit doesn't matter.

Børge

P.S. Enjoying kids in bed and calm piano music on real-time spline interpolator (aka homebrew CD player)
Hi Borge, Unix-man et al,

The "old" firmware (ie not the latest firmware I just built today), in the audio-widget-nik branch, uses, for uac1 24 bit USB and 24 bit i2S transferred to a 24 bit DAC. In uac2, it uses 32 bit USB and 24 bit I2S. The least significant 8 bits are truncated on transfer to the I2S bus.

My latest firmware (audio-widget-nik-2011-12-26.elf, which you can download from the code page), does FULL 32 bit transfers from USB to I2S to DAC, under UAC2.

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).

So Borge: bumper to bumper I2S seems to be OK in the AW

I will have to wait for George's 32 bit DAC to arrive to tell the difference

Alex
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