The γ1 modular miniature DAC

Initial check

Check to make sure all jumpers are set correctly for the configuration that you're building. Then, follow the steps below to check your γ1 for proper functionality. Do not connect the USB cable to the computer or plug in the DC external power supply until called for. For the full (A) or lite (B) configurations, keep the USB and DAC boards separate until the procedure requires you to mate them to each other. If you're building the full++ (F) configuration, then the two board sections should already be connected with wires (see the instructions page).

If, at any point you do not pass the check, do not proceed to the next step until the problem is first corrected.

γ1 DAC and USB board test points:

 
  1. If you will be using an external 5V regulated power supply (AC adapter) with your γ1, you should first check its output voltage. Leave the DC output plug unconnected, and plug the power supply into an AC outlet. Set your multimeter to DC V mode and measure the voltage at the output plug. Place the black probe on the outer conductor and the red probe on the center conductor, taking care not to short circuit the two. In order for the power supply to be used with the γ1, the reading must be between 4.85V to 5.40V. If your power supply does not meet this requirement then do not use it.

  2. With your multimeter set to Ohms mode (use the lowest resistance range on a manual-ranging meter), check for short circuits between the points listed below. If you read less than a few Ohms for any of these, then there is a short circuit. Carefully locate the short (such as a solder bridge) and fix it. You may use the exposed strips along each edge of the board as the GND contact.

    DAC board:
    • JP2D pin 1 and GND
    • JP2D pin 2 and GND
    • JP2D pin 3 and GND
    • +3.3V test pad and GND
    • +4.5V test pad and GND

    USB board:
    • +5V test pads(s) and GND
    • +3.3V test pads and GND

  3. If your build involves the USB board (i.e., all except the S/PDIF DAC-only (E) and full++ (F) configurations), install a temporary jumper shunt across J2U pins 1 and 2 (labeled VBUS and VCC, respectively). Then, connect the USB cable between one of your computer's USB port and the γ1's USB port. If LEDU is populated, it should illuminate. Within a short moment your operating system should detect and identify the γ1 as a "USB Audio DAC".

    Set your multimeter to DC V range and measure the voltage between the +5V test pad (next to J2U pin 1 "VBUS") and GND. This is your computer's USB port power voltage and should be very close to 5V.

    Measure the voltage between the +3.3V test pad and GND. You should read a fairly accurate 3.3V.

    Unplug the USB cable and remove the temporary jumper shunt.

  4. If your build involves mating the USB board to the DAC board (i.e., full (A) and lite (B) configurations), plug the USB board into the DAC board. Inspect carefully to make sure that J2U mated properly with J4D, and J3U mated properly with J5D.

    Connect the USB cable between your computer's USB port and γ1's USB port. For the full configuration (A), the SW1D switch should illuminate in red. As before, the operating system should detect your γ1.

    Measure the voltage between the DAC board's +3.3V test pad and GND. Since the DAC board is now plugged in to the USB board, you will have to locate the test pad and make the measurement on the solder side of the board. It should read a fairly accurate 3.3V.

    Measure the voltage between the DAC board's +4.5V test pad and GND. Do this on the solder side of the board as before. If you used a LP2985-4.5 for U6D, then should you should read 4.5V. If you used a TPS793475, then you should have 4.75V.

  5. If you built the S/PDIF DAC-only configuration (E), plug in your 5V regulated power supply and connect its output to the γ1's DC power jack. The SW1D switch should illuminate in red.

    Measure the voltage between the DAC board's +3.3V test pad and GND. Since the DAC board is now plugged in to the USB board, you will have to locate the test pad and make the measurement on the solder side of the board. It should read a fairly accurate 3.3V.

    Measure the voltage between the DAC board's +4.5V test pad and GND. Do this on the solder side of the board as before. If you used a LP2985-4.5 for U6D, then should you should read 4.5V. If you used a TPS793475, then you should have 4.75V.

USB operational test

This section is for all except the S/PDIF DAC-only (E) configuration. If you have the full (A) or lite (B) configurations, the USB board should be mated to the DAC board.
  1. For the full, lite or full++ configurations, connect an audio cable from γ1's analog line output to a line input of your stereo preamp or headphone amp. Set the preamp or headphone amp's volume control to minimum.

  2. If you built a USB-to-S/PDIF converter (no DAC board), connect the γ1's coax or optical S/PDIF output to an external DAC's corresponding S/PDIF input using an appropriate cable.

  3. If you built a USB-to-I²S converter (no DAC board), connect the I²S signals (at J3U) to your intended destination device using a ribbon cable and connector.

  4. Connect the USB cable between your computer's USB port and the γ1. The operating system should detect it as "USB Audio DAC". On the full and full++ configurations, set the input selector switch to the USB position (center). Open your operating system's software volume control applet, select the USB Audio DAC device and set all levels to their maximum position.

  5. Start your media player software application. You may need to change its output device setting to "USB Audio DAC". Start playing some music. On the full configuration, the input selector switch illumination should change from red to green. Turn up your stereo preamp or headphone amp's volume control and you should hear music.

  6. For the USB-to-S/PDIF converter configuration, Check the external DAC for proper operation and sound. Note that if the external DAC is a computer sound card, you may need to change its S/PDIF input setting to "external sync".

  7. For the USB-to-I²S converter configuration, check that your I²S device is working properly. The specifics are beyond the scope of this procedure.

  8. Note that the maximum resolution and sampling rate supported by γ1 is 16 bits, 48KHz for USB.

S/PDIF operational test

This section is for the full (A), S/PDIF DAC-only (E) and full++ (F) configurations only. If you have the full configuration, the USB board should be mated to the DAC board.
  1. Connect the S/PDIF coax output of your digital source (such as CD/DVD player, computer sound card, or some other digital media player) to the coax input of your γ1. Set γ1's input selector switch to the coax position.

  2. Connect an audio cable from γ1's analog line output to a line input of your stereo preamp or headphone amp. Set the preamp or headphone amp's volume control to minimum.

  3. For the S/PDIF DAC-only configuration, plug in the 5V regulated DC power supply and connect it to your γ1's DC power jack to power it up.

  4. For the full and full++ configurations, apply power to the γ1 either with the 5V regulated DC power supply or via a USB connection to the computer. You may even use a 5V wallwart equipped with a mini-USB output plug and supply power to the γ1 through the USB port. 5V power supplied through the USB port is active even when the γ1's input selector switch is set to the coax or optical positions.

  5. If your digital source is turned on and enabled, γ1's input selector switch should illuminate in green. If it glows red, check the switch to make sure it's set to the correct input, and the cable is connected properly. Start playback on your source, turn up the volume of your preamp or headphone amp, and you should hear music.

  6. Repeat the above steps for the optical input, if your digital source is equipped with an optical output. You may connect different sources to the coax and optical inputs and switch between them. You can also switch to USB, if you have a full configuration and the USB port is connected to the computer.

  7. Note that γ1's S/PDIF inputs support only two-channel stereo audio data. Video content such as Dolby Digital™ or DTS are not recognized and will cause the switch to glow red.

  8. Note also that while γ1's coax and optical inputs support up to 24-bit resolution and 192KHz sampling rate, the maximum supported by the WM8501/WM8759 DAC is 24-bit 96KHz due to the configuration to optimize the DAC's digital filter response.

Auto power switchover test

This section is for the full (A), lite (B) and full++ (F) configurations only, and only applies if U1D is installed. The U1D power multiplexer chip provides auto-sensing and switching between USB power and external power. If both power sources are connected, U1D will give priority to external power. The USB board should be mated to the DAC board for these tests.
  1. While the γ1 is powered from the USB port, plug in the 5V DC regulated power supply and connect it to the DC power jack. If you have music playing, you should experience no interruption. γ1 should have automatically switched to use external power.

  2. If your playing source is via the coax or optical input, you may disconnect the USB cable, the power should remain on and and the music should continue to play without interruption. The computer will, of course, detect that the γ1 has been disconnected. If you wait a moment and reconnect the USB cable, the computer should recognize the γ1 again.

  3. With both the external power supply and USB cable connected, if you now disconnect the plug from the DC power jack, γ1 should auto-switch back to using USB power. If you have music playing, it should continue. A brief audio pause may occur, depending on the pwoer supply you use, but it should not cause the computer to register a false USB disconnect condition. In some cases, depending on the specific media player software you run for USB audio playback, you may need to close and reopen the application.

  4. The automatic power switchover between USB power and external power works best if you keep the external supply powered up, and plug or unplug the DC plug at the γ1 side. If you disconnect the power supply at the AC outlet, you may not get a clean switch from external power to USB power. This is because most external supplies have a bulk capacitor which takes a long time to drain down. The slow voltage drop could cause some or all of γ1's chips to reset. When that happens, you may need to unplug and replug the USB cable for the computer to recognize the γ1 again.
If you have completed and passed all the above checks, then your γ1 is functioning properly. You can now proceed to the "Preparing the case" heading in the instructions section.

Notes

  • If you use USB as the source of power for your γ1 or γ1/γ2 combination, please use as short a USB cable as feasible. The longer the cable, the more its electrical resistance, which causes voltage loss. Under some conditions this may affect the unit's performance.

  • If a SMD chip becomes defective and must be replaced, and if you don't have specialized reworking equipment, the recommended method is to use Chip Quik® SMD removal kit. Their website has instructions on how to use it. Chip Quik is available directly from the manufacturer, as well as from Digi-Key (part number SMD1-ND).

    If you don't have Chip Quik, use a sharp knife to cut the leads off the bad chip near the chip body. Take care not to score the board. Then, remove the chip from the board. Heat each solder pad with your soldering iron and scrape away the residual pin. Then, remove any excess solder using your iron and a desoldering braid. Be careful with the iron so you don't melt any surrounding parts. Also, don't heat the board for prolonged periods of time to avoid delamination. Soldering in the new chip will be just like the first time. You need to be careful not to touch the other parts already in place with your iron.

  • It is normal to hear some background hiss if your full (A), S/PDIF DAC-only (E) or full++ (F) configuration γ1's input selector switch is set to a position with nothing connected. This is because γ1 has no output muting function. It should be completely silent when the selector switch is set to a connected position, but no audio is playing.

  • If you're running Windows Vista or Windows Server 2008, and you experience crackly-sound, bursts of static noise or distortion during USB audio playback, try installing Microsoft hotfix 944681. If that doesn't fix it, right-click the volume control icon in the tooltray and select "Recording Devices" to open the recording device configuration window. Having this window open seems to work around the noise problem.


Main: γ1 Main | Prev: Instructions | Next: Specifications