AMB Laboratories DIY Audio

[amb]

I used the MCP100-315 for U3. U6 has been removed. The R/L test pads measure:

Right = 2.13v both pads
Left = 2.14v Both pads
C20 = 2.17v
C26 = 2.17v

ok, so that means at least the analog portion of the WM8741 and everything after it (the LPF/buffer/balanaced-unbalanced converter opamp and surrounding parts) seem to be fine. You also know that the I2S bus signals are fine, or else the γ1 wouldn't work. That isolates the problem to somewhere between the I2S bus, the SRC4192 and the digital portion of WM8741. You should focus your attention to these areas. See the schematic diagram.

The y1 works when mated with the y2. The only issue I have noticed is that it drops the signal intermittently (the led on the switch goes red)and there is some audible noise when I access the network at the office. This is using the USB input for power and data. This doesn't happen with my computer at home.

Maybe network activity is inducing noise or disturbances on that computer's USB power.

[Co60]

Well, after a long Labor day vacation I am finally able to take a look at this again. Per AMB's response I honed in on the suggested areas and everything checked out except for Pin 2 on X1. Like AMB says most of the issues with this DAC are related to soldering issues. While there was plenty of solder on the pad, none of it flowed into the little channel on the side. So no connection to ground. Pin 2 is now connected to ground, but now I have continuity to the top of X1 which I figure is undesirable. I have tried a couple of methods to clean out the excess solder to no avail. After looking at the spec sheet and associated temps recommended for reflow, It appears I may have cooked it. Needless to say still no sound out of the y2. Can I just remove X1 to and install jumpers in JP2 to bypass the upsampling and test this guy out? Thanks for your continued assistance.

[MisterX]

Pin 2 should have continuity to the top of the crystal.

[K3cT]

Are you using a power supply or USB only at your office?

[MisterX]

What op-amp do you have installed in the Y2?
I can't see the markings even after reversing the colors and over-adjusting the brightness.

http://img534.imageshack.us/img534/6845/reversed.jpg

[Co60]

K3cT: I am using USB power both at work and at home. MisterX: Analog Devices AD8656ARZ, the OPA2365 was unavailable. I am not planning on driving headphones directly.

I have really learned a lot trouble shooting this DAC, everything else I have done has gone off without a hitch so I haven't had cause to really dig through schematics etc. For future reference, how would I know that pin2 on X1 is supposed to have continuity? I didn't see anything in AMB's docs or on the Crystek spec sheet.

[K3cT]

There is a possibility that the computer does not provide enough power for the DAC. Last time I also faced a similar problem where the γ1 would work but when mated with the γ2, things became really weird.

And probably obvious but have you tried cleaning the solder flux?

[MisterX]

Can I just remove X1 to and install jumpers in JP2 to bypass the upsampling and test this guy out?

You would also have to remove U4.
I was going to suggest reflowing the joints on U4 but they look pretty good as is.....

[Co60]

I was planning on a non USB power supply so I will try that. I did just try the RCA outputs and i got a nice buzzing sound, but nothing from the mini-jack. I have checked all the legs on the chips again for solder bridges and continuity. The only thing I can think of now is that either A) data is somehow not making it to the y2 or B) one of the chips is gone south. Is there a way for me to check that data is flowing? I have checked continuity between the boards and it all looks good, unless of course I missed something...

[MisterX]

Tracing the signals through the components would require an oscilloscope.
I will take a look at it for if you want to drop it in the mail.