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Gustard U12 USB Interface 8 Core XMOS chip
Jul 10, 2015 at 6:05 AM Post #2,012 of 3,700
jodokus said:
  Is it normal that the U12 stays powered on (sample rate led on), when my HTPC is shutdown?
Click to expand...

If the HTPC's BIOS has wake on usb enabled the USB port remains powered and the U12 will stay on.
 
Turning off this function will depend on whether you need to be able to wake the PC using the mouse or keyboard press.
 
Jul 10, 2015 at 6:35 AM Post #2,014 of 3,700
jodokus said:
  I checked, but it's off in the bios, will check again tonight. Would you recommend keeping the U12 on, performance wise?
Click to expand...


I would leave it on for performance reasons, the crystal oscillators (XOs) need 10-20mins to fully stabilize from a cold power on.
 
If you are using Windows 7 and later it can enable wake via the ACPI or similar mechanism
 
Jul 10, 2015 at 6:49 AM Post #2,015 of 3,700
dacladder said:
  The Luckit 2.23 driver did not fix my issue of the U12 dropping out in the middle of playback and emitting a low-level tone.  Thank goodness the tone volume is low as it is unsettling to be listening intently and all of a sudden about a 2Khz tone. 
 
When the problem happens Windows 8.1 thinks the USB interface is normal as near as I can tell.  I can see packets being shifted with USB sniffer software so the problem is further downstream of the Xmos USB interface.  JRiver is running normally at the time.  The U12 just locks up and requires a power cycle to restart.  When the problem happens the LCD displays " - - - -".  It is like the U12 or parts of the U12 just reset and do not recover. 
 
The U12 electronics are fairly simple.  There is an Altera FPGA that takes in the Xmos data output plus the two clocks, reformats, and drives the I2S, serial outputs, and front panel LCD display.  I thoroughly checked the soldering on all components where I can and looks great. 
 
I haven't given up hope as I like a challenge but it will be difficult to reverse engineer the design and figure out the issue cause.  I have the U12 top cover removed and looking at signals trying to figure out how it works.  I also have Xmos datasheets and reference designs as a guide.   About the only thing I cannot check is the Xmos soldering as the package is a ball grid array.  And forget exchanging the Xmos as I do not have the equipment to resolder BGAs.   Hope you have better luck with your U12.
Click to expand...


I suggest putting back the original 45Mhz crystal and see if the lock problem goes away.
 
A drop out followed by a tone or continuous clicks may be due to a glitch in the power supply causing the processor in the XMOS to crash, the Panasonic FRs you are using may have a too low an ESR for the 317 regulator, consider changing them back, 317s are very finicky around low ESR caps, the older NatSemi datasheets actually talk about it, another option is to add a 10uF Tantalum at the regulator input. 
 
Jul 10, 2015 at 8:37 AM Post #2,016 of 3,700
b0bb said:
 
I suggest putting back the original 45Mhz crystal and see if the lock problem goes away.
 
A drop out followed by a tone or continuous clicks may be due to a glitch in the power supply causing the processor in the XMOS to crash, the Panasonic FRs you are using may have a too low an ESR for the 317 regulator, consider changing them back, 317s are very finicky around low ESR caps, the older NatSemi datasheets actually talk about it, another option is to add a 10uF Tantalum at the regulator input. 
Click to expand...

Thanks for all your help.  Debug is on hold until I return from holiday vacation.   The problem happened when the U12 was new without any modifications.  I thought at the time I just needed a better driver.  The issue happens whether I used the Jcat USB daughter board with ultra-clean, linear +5V feeding the U12 or using the PC motherboard USB ports.
 
When I return I will try a different computer and USB cable for testing.  But I never have any problems with other USB audio devices on the same setup. 
 
Jul 10, 2015 at 9:48 AM Post #2,017 of 3,700
b0bb said:
 
I would leave it on for performance reasons, the crystal oscillators (XOs) need 10-20mins to fully stabilize from a cold power on.
 
Click to expand...

Is there any way to get the U12 to stay on without a source plugged in? I like to leave all my stuff powered on all the time (for performance reasons), and I definitely noticed the U12 sounds much better after 12-14 hours on, but I use my Macbook Pro as the source and I can't leave it on my desk all the time.
 
Other than that, I can't imagine beating the value of the U12. I was seriously considering a Tanly, but then I picked up a used U12 for $100 shipped. A fantastic upgrade from optical straight out of the MBPr. The thing I noticed the most is how much more realistic cymbals sound.
 
Can't wait to start modding!
 
Jul 11, 2015 at 7:42 AM Post #2,021 of 3,700
Please create a separate thread for DYI modification of the product.
People which are not willing to do DIY just want to have reviews of the out of the box product.
It is too difficult to separate OOTB review from DYI details.
 
Jul 11, 2015 at 8:10 AM Post #2,022 of 3,700
vincponc2610 said:
  Please create a separate thread for DYI modification of the product.
People which are not willing to do DIY just want to have reviews of the out of the box product.
It is too difficult to separate OOTB review from DYI details.
Click to expand...

 
You can read out of the box reviews here as well. The U12 performes great, what do you want to know?
 
Best bang for buck? 
 
-1 Gustard U12
-2 Melodious MX-U8
-3 Tanly
 
Best Sound Quality?
 
-1 Tanly
-2 Melodious MX-U8
-3 Gustard u12
 
 
We do try to make it for other people as easy as possible to convert their out of the box device into a high-end device, for a convenient price tag,
We just can't deny that there's a modification possibility for everyone overhere, even the ones with absolutely no electronic skills.
 
 
If you want to know how it sounds, please just ask, people overhere at Head-Fi will tell you (if you find this thread too technical to read).
 
Regards,
 
 
 
Alex
 
Jul 11, 2015 at 10:08 AM Post #2,024 of 3,700
Jul 11, 2015 at 10:37 AM Post #2,025 of 3,700
Wish I had a pot of gold, because the X20 looks interesting to me then the X12, But the X12 is more realistic for me to get a hold off. Unless Massdrop get a hold of those X20's but I doubt that happen any time soon.
 
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