Preamplifier Soulution 326 Preamplifier

Preamplifier with dual volume control path and bandwidth up to 2 MHz

The Soulution 326 is an analogue preamplifier built on the principle that a signal should only be amplified or attenuated, never altered. The design relies on a single-ended topology with a minimum number of components in the signal path and on physical separation of the left and right channels, which reduces crosstalk between them. The signal path includes an audiophile coupling capacitor that protects the preamplifier as well as the downstream power amplifiers and loudspeakers from any DC component coming from the sources.

Volume control is handled by a relay-switched resistive ladder with precision metal foil resistors offering 80 steps of 1 dB. During the level change itself, a secondary IC-based control stage takes over, eliminating clicks and voltage spikes; once the new value is set, the unit returns to the sonically superior resistive path. The bandwidth of the preamplifier section exceeds 2 MHz (-3 dB), which significantly reduces phase shift within the audible band — at 20 kHz it is less than -1.5°. THD below 0.0001 % and noise below -140 dBV/sqrt(Hz) define the extremely low sonic signature of the unit.

The optional phono stage uses a two-stage active-passive RIAA equalisation with close-tolerance passive components, contributing to the accuracy of the time constants. Three wide-bandwidth, low-noise stages provide 60 dB of gain with minimal deviation from the ideal frequency and phase response, while the adjustable loading impedance ranging from 10 to 1260 Ω allows precise matching of an MC cartridge, either from the front panel or the remote control.

The optional digital module offers four inputs (SPDIF, AES/EBU, Network, USB). A powerful DSP converts incoming data to the DXD format and performs zeroPhase processing and LEEDH volume control. Conversion is handled by a pair of PCM1792 chips in mono configuration per channel with the internal digital filter bypassed; the passive reconstruction filter uses custom-made precision components with stable characteristics, a prerequisite for correct phase compensation. Operation is via three buttons and a rotary control on the front panel with a clear display, including configuration functions for tailoring the entire system.

Key features

• Volume control: 80 steps of 1 dB, metal foil resistors
• Dual volume path: Click-free switching via IC stage
• Bandwidth: 0 – 2 MHz (-3 dB), phase shift below -1.5°
• Distortion and noise: THD < 0.0001 %, noise < -140 dBV/sqrt(Hz)
• Optional modules: MC phono stage and DAC with four inputs