Before you startThis section assumes that you have pre-drilled your front and rear panels (for the jacks, switch, etc.). If you haven't done so, see the boards & panels section for details and work on that first.
You can print out an image of the circuit board silkscreen layer (PNG format | PDF format), to use as a guide for installing components.
Do not remove the integrated circuits from their sealed packaging until you're ready to solder them on the board. This is to protect them from electrostatic discharge and moisture.
While you look at the board layout, please also take the time to check the schematic diagram and associate each part with their location in the circuit. While this is not normally required to build a working DAC, one of the opportunities of DIY is to learn about how the circuit works. Try to determine what each part does and why the particular part or value is chosen. There are many web resources to help you with this, including the AMB DIY audio forum. You will find the overall DIY experience more rewarding as a result.
Due to γ1's small size and close approximity of parts, as well as the surface-mount device (SMD) integrated circuits, you should have the following tools and supplies to help you work on the board and case:
Circuit board assembly instructions
Important pre-assembly notes:
Clean both sides of the blank γ1 board with paper towel and isopropyl alcohol or electronics flux remover, then solder the components to the board, beginning with all the SMD integrated circuits for maximum access.
Apply liquid flux to the board solder pads, and place the chip over the pads. Use the tweezers to pick and nudge the chip until it is centered and aligned perfectly. Be sure that the pin orientation is correct. Most chips have a dot marking next to its pin 1. The board's silkscreen is also marked accordingly.
Press the tweezer tip on the top of the chip to keep it from shifting while soldering. Apply only a tiny amount of solder to the tip of your iron, and tack down one corner pin of the chip. It helps to use a "wiping" motion of the tip on the pin and pad. If necessary, make small adjustments while heating that pad and pin again. If all is well, do the pin on the diagonally-opposite side. Then, do the remaining pins one at a time, reflow any pin that needs a bit of touch-up. If necessary, use the desoldering braid to remove any excess solder, and be sure there are no solder bridges between the pins.
When done, your solder joints should look something like this:
Use your multimeter and check the resistance between each pin of the chip and the pad to make sure you don't have a cold joint (i.e., your meter should read close to zero ohms). Also check continuity between adjacent pins for solder bridges (meter should read infinity, except where the pins are supposed to be connected to each other, see the schematic diagram for verification).
Repeat the above procedure for all the SMD integrated circuits. When you are done with all of them, use a Q-tip and isopropyl alcohol, or specialized electronics flux remover to clean off the flux.
Now mount and solder the rest of the parts, starting with the lowest profile parts and work up, in the following order (see details below):
Make sure the correct part goes into each position on the circuit board. Measure each resistor with your multimeter to ensure it's the proper value before installing it. Pay attention to the polarity of resistor networks, electrolytic capacitors, transformer, reset managers and transistors. For electrolytic capacitors, the positive lead should be the longer one.
When soldering the DC power jack, RCA jack and 3.5mm stereo mini jack, you should heat the solder tabs and pads sufficiently to allow solder to fill the entire hole. Remove heat immediately and cool the joint by blowing air at it as soon as you achieve a good fill. This assures that the jacks will be mechanically-secure.
If you're installing LEDU, bend the LED leads 90°, paying attention to the polarity and which way it will face through the front panel. Adjust the mounting height so that it is aligned with the front panel hole and solder one pin first. Heat the pad and make further adjustments if necessary. Then, solder the other pin.
If you're using the Box Enclosures B2-080 casing, the USB and DAC sections of the board are not physically plugged into each other as they are in the Hammond 1455C80x, so they must be connected with wires. For the "full++" configuration (F), only 5 wires are needed (to connect the DATA, VCC, VBUS, and two GND lines):
J2U pin 2 (VCC) -> J4D pin 2
J2U pin 3 (GND) -> J4D pin 3
J3U pin 1 (GND) -> J5D pin 1
J3U pin 5 (DATA) -> J5D pin 5
The following picture shows an example of a 5-wire ribbon cable hard-wired to the bottom side of the board and soldered at the top side pads.
NOTE: If you're building a γ2 board to be mated to the γ1, then you do not need to add any wires. The γ2 board will provide this connectivity.
Inspect all solder connections carefully, using a magnifying glass, to make sure there are no solder bridges or cold solder joints. Use a multimeter in ohms scale to check for short circuits. Correct any mistakes before moving on to the next phase.
Jumper settingsSet up the jumpers according to the following table, based on your build configuration.
NOTE: If you're building a γ2 board to be mated to the γ1, do not install pin headers and jumper shunt on JP1U. Solder a clipped resistor lead across the appropriate pads on JP1U instead (see table above). Otherwise the two boards will not fit properly.
All positions of JP2D should be left open unless U1D is not installed. It is recommended that you install U1D, unless you have a good reason to omit it. If U1D is not present, then you may use JP2D to "hard-wire" the power source, as follows.
After circuit board assembly is complete, proceed to the initial check section to test the DAC before connecting to the computer USB port or any other component. When you are done with testing, continue to the section below for preparing and mounting the board in the case.
Preparing the caseThis section assumes that you have already done the initial checks of your assembled board(s).
You may use the panel screws supplied with your Hammond or Box Enclosures case, but they aren't as attractive as socket cap screws. Also, the supplied screws are self-tapping, and are not designed to be removed and installed for many cycles. Eventually the screw threads would wear out.
For this reason imperial #6-32 or metric M3.5 flat-head socket cap screws are recommended. These screws should be at least 3/8" (9.5mm) long but no longer than 3/4" (19mm). Flat-head screws are recommended for the front panel to avoid possible interference with oversized connectors.
If you use the screws supplied with the case, installing and then removing the screws before the final assembly keeps you from getting pieces of aluminum all over the board.
If you use #6-32 or M3.5 screws, you must first tap the case to match. Taps for your portable electric drill or drill press could be purchased from a tools and hardware store.
If you're using the Hammond 1455C801 case (metal end panels), it is recommended that you mount the panels directly to the case without the plastic bezel rings. This eliminates a gap between the panel and the board, which may prevent the Toslink plug from fully seating in the optical input module.
If you have a black or blue anodized Hammond case, or the Box Enclosures case (all colors), it is recommended that you grind away some of the anodizing from the board slots, in order for the exposed ground plane strips on the boards to make contact with the case. This provides RFI shielding. You do not need to do this with Hammond's clear anodized version. Using the emery board or thin file, carefully grind along the board contact surfaces of the slots on each side, until you could see bare aluminum showing through. When you're done, clean the case of all metal dust and shavings.
Insert the boards into the slot. Be careful while doing this to prevent any part of the circuit from touching the case. Be sure that the solder joints on the bottom of the boards do not touch the case.
Use your multimeter to check the continuity between the sleeve ("circuit ground") of the inner 3.5mm stereo mini jack and a point where you could make good contact with the bare metal of the case (such as at the panel screw threads). You should get a low ohms reading. If not, remove the board, grind the slots further and repeat.
The board may be slightly loose in the front/back direction of a Box Enclosures B2-080 case. If this occurs, shim the end of the board (where it contact the rear panel) with a small piece of foam tape.
Install the front and rear panels and fasten the panel screws. You're now done.
Connect your digital source and connect the line out to your stereo preamp or headphone amp, and enjoy the music!
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