Alien DAC offers 4 powering options:
|IC1||1||PCM2702E. SSOP28 package.||Mandatory.|
|IC2||1||REG101UA-33 or REG102UA-33. SO8 package.||Mandatory.|
|IC3||1||Fixed: REG101UA-5 or REG102UA-5. SO8 package.|
Adjustable: REG101UA-A or REG102UA-A. SO8 package.
|Mandatory for all configurations except Unregulated USB. Read Note 4 for more details.|
|IC4||1||BUF634U or OPA551UA. SO8 package.||Mandatory if used with a virtual ground amp.|
|L11 - L18||8||Ferrite 600R. 1206 package. Murata BLM31AJ601SN1L||Recommended for EMI reduction. Jumper if not populated.|
|C1||1||Ceramic 1µF-22µF. 0805 package.||Recommended for additional filtering.|
|C2||1||Electrolytic 470µF-1000µF. 10V. 10mm diameter. 5mm pitch. Height <=15mm if used with 1455C enclosure.||Recommended for additional filtering.|
|C11, C12||2||Ceramic 33pF. 0805 package.||Mandatory.|
|C13||1||Electrolytic 10µF-47µF. Lowest ESR/ESL. 6.3V. Radial. 6.3mm diameter. 2.5mm pitch.||Mandatory.|
|C14 - C19, C21, C31||8||Ceramic 100nF. 0805 package.||Mandatory.|
|C22, C32||2||Ceramic 10nF-100nF. 0805 package.||Recommended for noise reduction. Refer to Note 4 for C32 usage.|
|C23, C33||2||Electrolytic 33µF-100µF. 6.3V. Radial. 6.3mm diameter. 2.5mm pitch.||Recommended for noise reduction.|
|CL, CR||2||Pro audio grade aluminium electrolytic 4.7µF-47µF. 6.3V. Radial. 6.3mm diameter. 2.5mm pitch.||Mandatory if your amp does not have any input DC protection.|
|R11, R12||2||Metal film resistor 22R. 0805 package.||Mandatory.|
|R13||1||Metal film resistor 1K5. 0805 package.||Mandatory.|
|R14||1||Metal film resistor 1M. 0805 package.||Mandatory.|
|R15, R16||2||Metal film resistor 330K. 0805 package.||Mandatory if you populate CL and CR.|
|R31||1||Metal film resistor 31K2. 0805 package.||Mandatory if you use an adjustable regulator IC3. Do not populate it otherwise. Read Note 4 for further details.|
|R32||1||Metal film resistor 11K5. 0805 package.||Mandatory if you use an adjustable regulator IC3. Do not populate it otherwise. Read Note 4 for further details.|
|RLED||2||Metal film resistor 600R. 0805 package.||Mandatory if you use LED.|
|X1||1||Crystal 12MHz CL=30pF. HC49 package.||Mandatory.|
|LED||2||3mm low current LED.||Optional.|
|PCB||1||Alien DAC Printed Circuit Board v1.1.||Mandatory.|
|USB||1||Type B receptacle. BERG 61729.||Recommended for mechanical stability and improved shielding.|
C0G/NP0 capacitors are the best for decoupling. X7R is the next best choice.
If the amplifier, you are going to connect Alien DAC to, has some input DC protection, then do not populate CL/CR. Simply jumper the CL/CR positions or run output wires from the corresponding plus pads. This way you will avoid all sorts of problems related to choosing the output capacitors. If you are unlucky with your amp, then read on.
The PCB is designed to take 6mm diameter electrolytics. They are compact and you can find well sounding caps. I recommend using one of the following:
If your enclosure has some room available, you can opt for using off-board capacitors. Here is a great comparison of popular coupling capacitors you may find useful. With a bit of creativity you should be able to mount almost any capacitor out there.
A fixed voltage regulator is easier to use and apparently has better noise/ripple characteristics. Therefore, if you can get away with it, you should always use a fixed voltage regulator.
If you are building a USB-powered Alien DAC, you cannot use the fixed voltage version because USB gives you only around 5V and this is not enough for a 5V regulator to work properly. Well, it does work anyway but it does not regulate. One option would be to power your DAC directly from USB without any regulation. Alternatively you can choose to regulate the voltage down to 4.5-4.8V. This is where an adjustable regulator comes in handy. Simply select proper values for R31/R32 and the problem is solved.
The formula for calculating the output voltage is Vout = (1 + R31 / R32) * Vref, where Vref is 1.267 for REG101 and 1.26 for REG102.
Another reason for using an adjustable regulator is "overclocking" PCM2702. The chip's datasheet indicates that the DAC performs slightly better at higher voltages. If you go this way, you should set the voltage at approx 5.4V to allow for regulation errors.
When selecting IC3, pay attention to the part number suffix. "-5" is a fixed regulator. "-A" is an adjustable regulator.