Moving on to DACs, you can have a very simple layout like the HRT Music Streamers, or something more complex like the Cambridge Audio DacMagic.
Notice that you don’t see any travo inside the DacMagic circuit, that’s because the DacMagic uses an external wallwart supply (albeit an AC voltage one). On the right side you see a big chip with the “DSP” marking. Doing some reading about the DacMagic will reveal that Cambridge uses a Texas Instruments DSP Chip to perform upsampling operation on the digital signal. So the circuit on the right side is most probably dedicated to that function. This is only unique on the DacMagic, and is not something that you will find on all DACs.
On the left side you see another circuit, and if you look closely, there are two chips with the marking “WM8740” written on it. A quick google check reveals that it’s a D/A chip that does the actual digital to analog conversion. Since the D/A chip requires a power supply to operate, Cambridge has put the power supply circuit right on top of the DAC sections. On the picture below you can see there are two chips with three legs, mounted on a heatsink. That is the PSU circuit for the DAC section. You can also see the two WM8740 chips on closer view right on the bottom side of the picture). If you go back to the big picture, above the heatsinks are some capacitors, and they are also a part of the PSU circuit.
Every DAC circuit needs an analog section to amplify the signal coming out of the DAC chip into a proper line level signal. Hence the op-amps seen on this picture. There is one small chip with OP275 written on it, and two small chips with N5532 written on them. The red cubes are the famous Wima capacitors. At the really bottom, left of the “Headfonia” watermark, is a portion of the WM8740 DAC chip. So an analog signal comes out from the WM8740 DAC chip, and is amplified by the N5532 chips, and finally into the OP275 chip. The surrounding components are the required elements for the chips to function properly. Going back to the big picture, you can see that after the DAC section, there is a row of capacitors (the red Wima blocks and the round ones) that should be the output capacitors section.
Before we finish with the DacMagic, please notice the PCB that’s mounted on the front panel. Without going into too much detail (and it’s way more than what I know anyway), that section is dedicated to the user interface, as the DacMagic has a digital interface for selecting input sources, digital filters, etc.
In contrast to the DacMagic, you also have much simpler DAC unit like the HRT Music Streamer:
The HRT Music Streamer design is very simple and yet very logical. Digital signal comes in on the left side of the PCB via the USB connector (with the “OK” marking). The HRT Music Streamer uses power from the USB to operate its circuitry, so some of the signal from the USB goes to the PSU circuit, and some into the digital processing unit. The square chip with lots of pins on all four sides is the TAS1020 chip, which receives the incoming USB signal. There is one chip two-thirds down the length of the PCB, with a line going right through the middle: that is the PCM1794 chip that does the digital to analog conversion. You can google the chip codes to see what they do, normally the google result will show you a datasheet of the chip (below is a datasheet of the PCM1794 D/A chip). Then on the right side of the PCM1794 is the corresponding analog stage for the DAC and finally out to the RCA connectors as line level analog signals.
Next we’ll take a look at an integrated DAC/Amplifier circuit.