The full-function preamplifier has become something of a rarity, especially in the high-end, but Soulution’s 520 preamplifier – central to the company’s more ‘attainably priced’ range - sports an exceptionally capable moving coil phono stage in its single chassis. While this isn’t a preamp that bristles with inputs (phono stage aside, it has two balanced, and two single-ended inputs) and doesn’t sport anything close to a DAC, the minimalist 520 is still remarkably flexible by today’s standards.
Like the more upscale 725 line-stage, Soulution designed the 520 preamp to be an extremely wide bandwidth design – it’s only 3dB down at 1MHz – and places great emphasis on ultra-fast response times as a result. While we are not a measurement led magazine in any respect, a product claimed to sport a frequency response ruler flat to 200kHz, with less than -120dB of cross-talk and distortion so low, the analyser’s self-noise is more significant, deserves to be taken seriously.
The Soulution 520 achieves these figures by taking everything extremely seriously. Separate power supplies are used for the digital logic circuits and the amplifier stages, but these supplies are further fed through a multi-stage filter network, and the logic and amplifier stages are independently shielded to reduce the possibility of interference. The volume control is an 80 step, 1dB per step, precision foil resistor array instead of a potentiometer. This is selected via precision relays, but where most audio companies would ask the user to put up with the clicking of those relays, Soulution parallels a programmable gain amplifier as a separate volume path to function while the volume control is activated. Once the correct volume is set, this amplifier decouples itself from the signal path and the selected resistor pair kick in.
The MC phono stage has no gain adjustment (on the grounds that the 520 is quiet enough to accommodate the lowest gain cartridges without hitting the noise floor of the preamplifier), but impedance is set at the rear panel, using a series of DIP switches between the left and right channel MC inputs. The input ranges from 20Ω to 1kΩ in seven steps.
For a preamplifier that basically has one large knob and three small buttons on the front panel (the upper of which is reserved for ‘mute’ only, the lower being the power button), it’s surprisingly configurable. You can preset which source to start on, name those sources, the start-up volume level, the maximum and minimum volume levels, balance, screen brightness, activate ground lift (if there is hum), even whether there is a surround input and its optimum volume level. As the remote is passcode-bonded to the preamp, you might also need to reenter the remote’s ID, and that option is also on the front panel menu. Surprisingly, given the relatively limited range of input devices on the front panel used for menu diving (essentially the ‘prog’ button, pressing the volume knob, and turning the volume knob), navigating the options on offer is surprisingly easy, and the preamplifier with its big, friendly red LED readout is soon up and running.
Soulution is unfazed by whether the end user chooses balanced or single-ended connections between devices, although it recommends using the 520 with balanced designs for long cable runs. The 520 is inherently single-ended in design, and runs pseudo-balanced (rather than the other way round) so if you can follow the RCA route, so much the better. But not that much better, because the balanced pathway is remarkably close to the single-ended line, and with a 10Ω output impedance, virtually any cable made to practical lengths and any amplifier will partner the 520 perfectly. In other words, Soulution’s suggestion of cable architecture is more down to the company’s obsessive nature than any noticeable sonic benefit. And, unlike sorting your cornflakes by size before eating them, this kind of obsessive nature seems entirely beneficial.
This has to be read carefully, but Soulution is one of the least well-named brands in audio. The name suggests ‘soul’ and this is not the preamplifier for someone wanting something syrupy, soulful, and magical. Instead, this is the preamplifier for those seeking absolute realism, accuracy, and honesty. The ‘soul’ of this preamplifier is the soul of a musicologist or a tonmeister. This is the preamplifier for the person who is constantly berating the audio world for forgetting the term ‘hi-fi’ meant ‘high fidelity’ and demands a faithful reproduction of what is on the recording. In other words, there is no ‘soul’ in the Soulution… and that’s how it should be. If you misread this as a disguised insult, think about what the alternative actually means: you might want a bit of added seasoning to your music – some more ‘soul’ even – but what you add is also detracting from what was on the recording. The Soulution concept is an attempt to limit the artificial colouring and flavouring that seems to represent modern ‘high-end’.