Open-source USB interface: Audio Widget

[alexlee188]

Hi UnixMan,

Both the Hiface an the Legato are USB to SPDIF interfaces. The jitter is most likely coming from the SPDIF link - thus the great engineering effort to reduce jitter.

The audio-widget is NOT an SPDIF interface, and despite requests to add SPDIF out, we are reluctant to do so precisely because of the jitter of the SPDIF interface.

The digital part just supplies the i2s samples to the DAC. The DAC is clocked by a < 1 ps jitter XO.

However, no amount of theoretical arguments will settle this jitter issue. We will wait for someone to do measurements to do listening tests :-)

Alex

[2A3SET]

The SQ of hiface interface depends much on the external power supply, "the flea" circuit or LifePO4 battery both can deliver much better sound while direct feeding 1.8V/3.3V with shunt regulator is the best.

The AW-1 and Audio-Widget with ADP151 both deliver decent sound as a good start point, they also have connectors to external power supply bypassing onboard ones (3.3V for DAC and XO) to provides extra choice for DIYer.

I am not sure how I2S signal looks like generated from MCU, IMHO it may benefit from reclocking the I2S using master clock from XO.

Originally Posted by UnixMan

yes. But not only.

Also the digital board may need some improvements. That's why I mentioned the Legato (which is just an USB to s/pdif UAC1 async interface, see here: http://www.audiofaidate.org/forum/viewtopic.php?t=8408 ).

Before hearing that one, I was (naively...) thinking that with an async connection and a good local clock one could basically forget about the digital domain and all of its problems. As I discovered the hard way, it's definitely not that simple. Even with an async link, there is still a long way to go. Have a look at the interesting measurements made by my friend and colleague George "Joseph K":

DIYHiFi.org &bull; View topic - Some jitter analysis - and beating of a dead horse..

To obtain such amazing results, the Legato uses a lot of care in power supplies, clock, signal routing, layout, etc. Most (if not all) of the tricks used there have been previously documented by Joko (the Legato designer) on either this or that other forum, and perhaps similar strategies and care may/should be applied to the audio widget as well.


I definitely second your points.

BTW: for what regards PSUs, have a look at "Salas shunt reg." and/or Joko designs on this forum.

[GeorgeBoudreau]

Hi,

I have validated the USB9023 RevA boards and am satisfied with the results. This revision contains the following modifications:

-The Si532 clock has its own ADP151 low noise regulator.
- I have replace a number of ceramic caps with polymer aluminum caps to improve the sound quality.
- The board now has jumper selection for power supply sources. You can use USB supply for all sections or power 1 or all regulators from an external 5vdc supply. You may also bypass the on-board low noise regulators and power with a 3v3 supply of your choosing.

The addition of the polymer aluminum caps and the additional regulator have bumped the cost of a kit to $85 + shipping + paypal fees. You can view an assembled board on my website I have a limited quantity of parts for kits and will most likely not do another run of this revision.

Contact me directly if you are interested in a kit.

Regards,
George

[borges]

Hi guys,

Finally, the first 10 working AB-1.1 units have arrived with me. More
are on their way. Pictures and schematics are attached.

The boards have been tested with 24bit 44.1 and 48ksps asynchronous USB audio on driverless Win7/64. The boards will do 24bit 176.4 and 192ksps on Linux (native) and Mac (native) and Windows (experimental drivers).

So what sets this kit apart from the existing AB-1?
* It now comes in a pretty case. It even has a nice logo on it :-)
* There are OS-CONs at important power loads.
* The DAC is now ES9023.
* There are headers to easily put in alternative power supplies.
* The front has a programmable R+G LED.
* Output filter caps not mounted, feel free to experiment with your own!
* Clocks have much improved MUXing, power and layout.

AB-1.1 uses Golledge precision XOs for good clock quality.

I'm _almost_ ready to ship them out. Unfortunately, my design for the
rear panel was a bit off. I'm redesigning it now for a better fit. It
will probably be a couple weeks before the rear panel and remaining
kits arrive. Let me know if you want to start playing with it ASAP,
and I'll send the rear panel when they arrive with me.

In the meantime, don't hesitate to place your orders! The price is
still USD120 + shipping. With a tracking number shipping is USD63(52)
international(Europe). Without a tracking number it is 14(9). Please
paypal to borge.strand@gmail.com.

USB-I2S module only is USD70 plus shipping. For each AB-1 you may have
bought from me before there is a USD30 discount.


Cheers,
Børge

[cviller]

Looks great!

What players can you use for 192k? Does it get messed up with pulseaudio on a normal ubuntu box?

[borges]

Thanks!

I've used various players on Windows, little experience with the various Linux solutions out there. Playing Wimp with one of them right now :-)

Børge

[alexlee188]

On Linux u need to set up pulseaudio properly if u want 192khz/24 playback. Setup .pulse/daemon.conf correctly.

you can use any playback program that is compatible with alsa, pulse, or jack. Banshee works. But the best sound quality comes from MPD.

Alex

[cviller]

Thanks alex - exactly the kind of info I was looking for.
(off to look for a Android remote app for mpd then... )

[mace1337]

I'm not a big fan of pulse, can we use alsa?

[cyteen]

Originally Posted by mace1337

I'm not a big fan of pulse, can we use alsa?

A man with a strong sense for the understatement