A test of Soulution's new Series 3: 326 preamplifier and 312 stereophonic power amplifier

In the rarefied world of high-end audio, Swiss manufacturer Soulution has long been synonymous with uncompromising engineering and extraordinary sonic performance. The 326 preamplifier and the 312 stereo amplifier are two important representatives of the revamped Series 3, i.e., the “Entry Level” of the Swiss brand (assuming it makes sense to use that term in this context): precision instruments that transcend conventional audio reproduction to deliver an experience that is as technically sophisticated as it is musically revealing. Recall that our 2G Audio Channel reviewed the 330 integrated amplifier recently replaced by the 331.

Soulution 326 e 312 filosofia di design ed eccellenza estetica

Design philosophy and aesthetic excellence

Both components embody quintessential Swiss design: minimalist, understated, yet meticulously crafted. The brushed aluminum cabinet features clean lines and subtle contours that contrast with the large finned heatsinks with contrasting color. Both evoke an engineering approach in which form follows function with absolute precision. The 312 stereo power amplifier weighs nearly 17 kilograms, while the 326 preamp stops the needle on the scale at about 10 kilograms. More than audio components, we are talking about pieces of technological art that stand out (and respect).

Preamplifier 326

The 326 preamplifier showcases Soulution’s engineering prowess by implementing the innovative volume control mechanism already seen in the Superior Series. At the heart of the system is an 80-step (1 dB) volume control using high-precision relay-switched metal foil resistors, ensuring exceptional balance between channels as well as maximum signal purity. The innovative aspect lies in the dual-path approach to volume control. To eliminate the traditional artifacts associated with volume variation, such as noise(clicks) and potentially damaging voltage spikes, Soulution implemented a secondary volume control path. During volume adjustment, an integrated circuit-based control adjusts the volume without audible artifacts. Once the desired volume is precisely set, the system reverts to the sonically superior metal foil resistor path.

The frequency bandwidth of the preamplifier extends beyond 2MHz (-3dB), a remarkable achievement that significantly reduces the phase shift within the critical audio bandwidth. This approach ensures that musical transients and harmonic structures remain intact, providing a high level of signal transparency.

Optional modules: phono stage

The optional phono board employs a sophisticated two-stage active/passive design that meticulously equalizes incoming signals to RIAA specifications, using high-quality, tight-tolerance passive components in RIAA networks to ensure high accuracy in reproducing the time constant.Three wide-bandwidth, low-noise amplification stages provide 60 dB of gain while maintaining minimal deviation from the ideal frequency and phase response. Load impedance is adjustable via remote control or front panel controls, which allows precise alignment with moving coil (MC) phonograph cartridges.

Optional modules: DAC

The optional DAC card turns the 326 into a complete digital hub. Equipped with four digital inputs-SPDIF, AES/EBU, Network (RJ54) and USB-it offers high versatility over digital sources. The DAC board has a powerful DSP that converts all incoming digital music signals to DXD format, implementing proprietary zeroPhase processing and LEEDH volume control. The digital-to-analog conversion employs a PCM1792 chip in mono configuration for each channel, with the chip’s internal digital filtering deliberately bypassed for optimal performance. The passive reconstruction filter uses custom-made high-precision components, ensuring stable filter characteristics that are critical for perfect compensation of ZeroPhase technology.

312 Stereo amplifier

The 312 stereo amplifier follows the path taken by Soulution for a few years now on its products regarding the power supply design by implementing four switching power supply modules. This approach provides as much as 1,200 VA of continuous power, with a peak power capacity of up to 4,200 VA for more than 5 seconds. Unlike conventional transformer-based technologies, these power supplies feature:

– High-performance filtering on both input and output stages;
– High-speed Soulution voltage regulators;
– Dramatically more stable power delivery;
– Greatly reduced noise and interference.

Drawing directly from the acclaimed Soulution 5 Series amplifiers, of which the 511 model is the reference in Audio 2G’s Room 1, the 312’s amplifier circuit features current amplification implemented in three distinct stages, each carefully designed to operate within an extremely narrow, nearly linear range, thus minimizing distortion and ensuring signal integrity. Delivering 120 watts into 8 ohms and doubling capacity into 4 ohms, the amplifier features remarkable current delivery and “dynamic headroom.” Its advanced power supply and ultra-low noise design enable the achievement of excellent signal-to-noise ratio performance.

Conclusions

The Soulution 326 preamplifier and 312 stereo amplifier transcend the conventional boundaries of audio reproduction. These are not simply components, but precision instruments designed for the most demanding audiophiles who demand absolute fidelity to the original musical performance.

Pros:
– Extraordinary signal transparency;
– Innovative power supply technology;
– Modular design with the possibility of adding optional modules;
– Sophisticated phono and digital conversion options;
– Innovative volume control mechanism;
– Wide, articulate and stable soundstage;
– Extremely wide bandwidth with minimal phase shift;
– Exceptional build quality and engineering.

Cons:
– Require a significant financial investment;
– Potentially too neutral for those listeners who are looking for tonal coloring.

Recommended for: critical listeners and audiophiles seeking reference performance who consider music reproduction a scientific art form.

Soulution 326: technical specifications

Mains	100 – 240 V (50 – 60 Hz)
Power consumption	< 0.5 W, Standby ~ 30 W, ON
Analog inputs	2 × balanced (XLR) 2 × unbalanced (RCA)
Input impedance	5.8 kΩ balanced (XLR) 4.9 kΩ unbalanced (RCA)
Phono input (optional) – Termination impedance	1 × Phono MC 10-1260 Ω
Digital inputs (optional)	1 × AES/EBU 1 × SPDIF 1 × USB 1 × Network
LINK (remote turn-on)	2 x phone jack (3.5mm)
Gain (unbalanced output)	– 79 to + 0dB
Frequency response (- 3 dB)	0 – 2MHz
Phase shift @ 20kHz	< -1.5°
THD	< 0.0001%
Spot noise	< -140dBV/sqrt(Hz)
Analog outpts	1 x balanced (XLR) 1 x unbalanced (RCA)
Ouput current (Peak)	> 0.2 A
Output impedance	10 Ω balanced (XLR) 5 Ω unbalanced (RCA)
Dimensions (WxDxH)	430 x 350 x 142 mm
Weight	~10kg

Soulution 312: technical specifications

Mains	100- 240 V (50 – 60 Hz)
Power consumption	< 0.5 W Standby idle 110W
Analog inputs	1 × balanced (XLR)
Input impedance	2 kΩ balanced (XLR)
LINK (remote turn-on)	2 x phone jack (3.5mm)
Loudspeaker	2 pair loudspeaker binding posts
Gain	+ 26 dB
Power output	120 W @ 8 Ω 240 W @ 4 Ω 480 W @ 2 Ω (< 5 sec.)
Output current max	30 A
Frequency response (- 3 dB)	0 – 800 kHz
Phase shift @ 20kHz	< – 3°
THD	< 0.0004%
Spot noise (input related)	< -140 dBV/√Hz
Damping factor	> 5000
Dimensions (WxDxH)	430 x 490 x 142 mm
Weight	~17 kg