Network Audio Players/Servers

Rated at 125W/8ohm [see PM's Lab Report] and weighing just 6kg, the Symphonia is the epitome of ‘green’ high-tech audio, achieving 85% power efficiency at full output. Low mass is the result of its all-alloy cabinet – there’s no steel here – plus its proprietary switchmode PSU developed for the R series. The latter switches at 190kHz-290kHz depending on power (up to 1.2kW) and avoids the need for a chunky mains transformer. Then there are the cool-running Eigentakt Class D power amps [left, inset picture] which do not require hefty heatsinking. In practice, the Symphonia’s finned sidecheeks are as much decorative as functional – most of the heat is driven out of the alloy base.

Of course, a side-effect of the switching PSU, the switching amplifier, the dual PCM/DSD digital stages [see picture above] and, arguably most problematic of all, the support for BT, is the potential to create a very ‘noisy’ electrical environment. T+A combats this on a number of levels. Its PSU uses FM sinewave rather than PWM control, with noise caused by ‘hard’ transitions suppressed by switching at the zero-cross point. Also, the PCBs are all four-layer with separate ground planes and matched impedances, preventing these surfaces acting as antennas – critical in passing the necessary FCC (EMI) regulations.

At signal/data levels, T+A uses a mix of galvanic and opto-isolation for much of its interstage coupling. Most critically, for sending high speed digital audio and clock data to both the PCM1795 and proprietary DSD converters, T+A is using 150Mbps-capable six-channel digital isolators from Skyworks. PM