Close-up of the Top-side (part 2)
PCB Top comments:
Noteworthy, past the two Elna Silmic Power Supply capacitors that decouple the power for the analogue stage and Class A Line Output Buffer is the large number of 470uF low impedance electrolytic capacitors that decouple the power supplies for other circuit parts.
1. The four capacitors on the far right (#1 at the far end, near the analogue volume potiometer) are responsible for backing up the power for the headphone Amplifier two each per channel, the headphone Amplifier is dual-mono, with two separate headphone ampifiers. Having big power supply capacitance only a few mm from the Amp means it can deliver transients easily, at full power.
2. At the lower edge, centre is the DAC section (underlined) and its power supply including our new and rather unique shunt noise filter (#2 green arrow) which cleans the USB Power for the DAC. For the DAC there is a critical pin called “reference.” We always pay much attention to this pin, however the iDAC2 benefits already from trickle-down from the upcoming Pro-range where we utilised a high-grade Panasonic Japan made Film Capacitor for surface-mounting, which combined with a smaller value C0G capacitor provides the cleanest reference pin voltage yet. On the AP2, it measures pretty darn nice.
3. The left part of the PCB is the whole digital engine with the digital powersupplies, back again with a brace of 470uF low impedance capacitors, the Audio Clocks (which have a dedicated low-noise linear regulator) and the switch to select the digital filters.
next time, PCB underside comments.
