4-EN
■ Reducing noise by lowering the impedance of the power supply system: “Four-Layer
PCB with STAR Circuit”
A copper through-hole four-layered PCB allows ideal patterning and part layout for noise minimiza-
tion. Furthermore, by doubling the thickness of the copper foil to 70mm, reduction of noise is achieved
with lower impedance of the power supply system. One layer out of four is the ground and Alpine’s
unique STAR (Signal Transit for Accurate Response) Circuit is mounted in order to overcome the
increase in impedance of the power supply system. By inserting the ground layer, reduction in
interference and ideal part layout were targeted.
■ “High-quality parts” were abundantly used to avoid inhibition of the high performance
of the DAC and filter.
A Signal-to-Noise (S/N) ratio three times better resulted from generously adopting ear-selected high-
precision parts, which contribute less noise or distortion. For example, fixed carbon film resistors do
not cause magnetic distortion (since they aren’t a metallic material). Special audio grade capacitors
behave more ideally in the audio range, maintaining the purity of sound.
■ High-Voltage I/V converter eliminates the necessity of a final stage booster circuit
which amplifies noise.
Inside the DAC, the digital bits are translated into electric currents. An I/V (current, I to voltage, V)
converter transforms those currents into output voltage. To achieve high output voltage, a commonly
available booster IC typically amplifies the I/V converter output. Unfortunately this amplifies noise as
well. Instead of following this standard path, Alpine specially engineered a Direct High Voltage I/V
converter. The output from the I/V converter is already high voltage, so no additional noise amplifica-
tion occurs.
