Power Amplifier Soulution 717 Power Amplifier

Reference power amplifier with fully dual-mono architecture and switch-mode power supply modules with extreme impulse reserve

The Soulution 717 is a reference power amplifier designed to drive virtually any loudspeaker, including low-impedance loads. The entire design, power supply included, is implemented as fully dual-mono: the left and right channels have separate printed circuit boards and are completely isolated from one another, delivering channel separation above 120 dB at 1 kHz. The amplifier pushes the boundaries in noise, phase error, common-mode rejection and distortion.

The input stage employs parallel-connected instrumentation amplifiers designed for a bandwidth of 20 MHz, the lowest possible noise and optimal common-mode rejection (CMRR above 105 dB). The voltage stage builds on a generous loop gain reserve — loop gain above 120 dB (DC) with a bandwidth of more than 2 MHz combined with an ultra-linear feedback network. The current stage works with 16 power transistors per channel in class AB, with a control circuit measuring the instantaneous current of every single transistor and setting its quiescent current so that all of them operate under identical conditions.

Power is supplied by four switch-mode modules of 4 × 600 VA with a peak output of 4 × 2,100 VA (2,100 W for 5 s). The output impedance of the regulated supply remains extremely low across the entire relevant frequency band, rendering large filter capacitances unnecessary. The small-signal section is fed by distributed local supplies with DC-DC converters and fast linear regulators placed right next to the load, which shortens signal paths and lowers noise to below −165 dBV/√Hz input-referred.

The result is an output of 2 × 150 W into 8 Ω, 2 × 300 W into 4 Ω and 2 × 600 W into 2 Ω, peak power above 2 × 6000 W and the ability to deliver current peaks exceeding 400 A; continuous output current is limited to 32 A RMS per channel for safety reasons. Phase error below 0.2° at 20 kHz and THD+N below 0.0001 % translate into temporal coherence and legible microdynamics, while a damping factor above 10,000 keeps bass driver cones under control and instrument localisation rock-solid. Connectivity comprises two balanced XLR inputs with an impedance of 4.4 MΩ, two pairs of gold-plated copper binding posts and a LINK control input for remote switch-on via a 12 V signal.

Key features

• Dual-mono design: Separate channel boards, separation above 120 dB
• Switch-mode power supply: 4 × 600 VA, peaks of 4 × 2,100 VA
• Current reserve: Peak currents above 400 A, 16 transistors per channel
• Phase coherence: Less than 0.2° at 20 kHz, bandwidth up to 2 MHz
• Exceptionally low noise: Below −165 dBV/√Hz input-referred