Soulution Audio 325 preamplifier and 311 stereo power amplifier

Solid-state power amplifiers,
Solid-state preamplifiers
Soulution 311,
Soulution 325

The 140W per channel 311 stereo power amp does follow many of the ideas developed for the 511 stereo amplifier, but not in a slavish or discounted way. It uses a three-stage current amplification system, with each stage operating in a narrow, almost linear, range. In essence, however, this is a high-Class A design with more than 160,000µF of storage capacitance and careful idle-current management (so a Class AB design can deliver mostly Class A power to the loudspeakers, without creating an amplifier that could pass muster as a heater in the process). This management acts independently to music signal and requires no warm-up time, so the amp sounds good from power-up. That being said, leaving both preamp and power amp constantly powered up is sonically beneficial, and as they don’t draw enormous amounts of power, no polar bears were drowned in the making of this sentence. Additionally, control circuits that protect against RF or DC signals are present at the input, and there is additional short-circuit protection.

The 311 also sports a total of six power supplies, with four switched-mode power supplies delivering 1,200 VA to the signal path circuitry. These power supplies feature high performance filtering at the input and output, and use Soulution’s own high-speed voltage regulators, which are claimed to deliver more stable power than traditional, transformer-based technology.

We used the Soulution Audio 311/325 combination in a suitably price and performance-matched system, with a dCS Rossini CD and Clock upstream, and a pair of Wilson Audio Sabrinas downstream. Cables in this context were from Transparent Audio (for the signal path) and Shunyata Research (for the power, with a Denali 6000/T power conditioner feeding the whole system extremely well. Music was a combination of 16-bit CD, streamed music from Tidal’s online service, and a selection of music ripped and downloaded to hard disc via the network. Both standard and high-resolution files were played.

It’s quickly clear that the word ‘clear’ features prominently in any summation of the Soulution 325/311. They are resolutely neutral, honest, balanced, level-headed, accurate, clear, correct, and all those other adjectives that describe an amplifier system that neither disrupts nor tweaks the sound of a system. While those who set their watch to 1970s time might contend ‘isn’t that what amps are supposed to do?’, the rest of us armed with a working pair of ears will admit that many are called, but few are chosen to the true path of neutrality... and Soulution is one of the chosen. 

Far from sounding boring and listless, however, true neutrality is an energising, exciting listening experience, and one that is instantly recognisable as such. Sounds rise from a completely silent background and have no artifice about them. Depending on where your priorities lay, this will manifest in one of several ways at first, with the other aspects joining the fray soon after. For me, it was high-frequency definition. It didn’t take much... a few bars of ‘Love In Vain’ from the Rolling Stones StrippedCD [Virgin] was all it took. The treble was almost muted by comparison to most amplifiers, and yet there was more going on; the chime of Keef’s acoustic playing, the resonance of Jagger’s voice, the dimensionality of the studio, all presented perfectly. 

In short order after that, I became aware of some world-class stereo imaging, pushing excellent depth and even some height out of those Wilsons. This was followed by an almost electronics-free coherence and dynamic range, a sense of effortless – rather than forced − rhythm, and the kind of dynamic shading that makes people who talk ‘microdynamics’ grow a broad smile. Musical examples followed in the style of the Glimmer Twins, revealing musical expression and finesse that is typically locked away behind the amplifier electronics and unveiled here. While there will always be those who like their music filtered, tuned, or emphasised in some way, the 325/311 sing true.  

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