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Pure Sound L300 Line-Stage Preamplifier Review
The Pure Sound L300 is a serious, all-valve pre-amplifier that pitches into territory occupied by some strong and well-established competition. Retailing at around £5000, the pre actually represents exceptional value (as much as you could say that about £5000 unit) as it is quite close in design terms to alternatives costing a fair bit more.
The circuit is based on fundamental principles: An amplifier takes a voltage and uses the signal input to modulate that voltage, resulting in an increased signal. With this in mind, Pure Sound’s designer has massively over-specified the power supply. A fully tube-based circuit, the design uses amongst other valves, a rectifier, HT voltage stabiliser and, unusually, a 300B valve for voltage regulation to boot. There’s a shed-load of valves in the power supply, compared to only four in the signal stage. But what a signal stage! Four dual-triodes, two per channel. The gain stages are direct coupled and the output is unusual at this price point in using transformer coupling. There are no capacitors at all in the signal path and the result is a pre-amp that can drive just about any load with ease and is unfazed by cable length or impedance-matching issues.
From a practical point of view, there are a generous five pairs of line-level inputs and outputs switchable between truly balanced or single-ended. Construction is of high apparent quality throughout, though it is worth mentioning that the unit is comparatively large for a pre-amp and is anything but light. Actually, make that big. Full stop. It’s 53cm deep, about 23cm high (including the top of the 300B which pokes out) and it weighs 20kg, so you really need to be sure you have the required space! There is no remote, and no option for one. To some this might be an issue, but it avoids the inherent compromises of remote circuitry and the additional cost and complexity. Going a little against current fashion, the circuit also uses a (high-quality) potentiometer, rather than a switched attenuator. The designer (quite rightly in my opinion) considers that attenuators offer no benefit, add considerable cost, and most importantly, sacrifice the infinite adjustability of a proper pot. No matter how good an amplifier, there is nothing more annoying than having to play music slightly too quiet or slightly too loud.
Although not one for measurements, I did run some brief tests on the amp. A sine-wave sweep revealed a virtually ruler-flat response curve from around 10Hz to over 20kHz; an impressive performance for any vale amp. Both sine and square-wave inputs were faithfully reproduced with no apparent distortion visible even at extremely low levels and maximum gain.
So, the most important test. How does it sound? Very good indeed. In fact, right up there with some of the very best ever. It’s likely that anyone considering this will be looking at pretty serious Audio Note equipment, or possibly a used Kondo to name two. Comparative listening against a Kondo M7 was interesting. The Kondo had some of its fabled ‘magic’ with possibly the edge on brass and stringed instruments. However, there is no doubting that this is colouration. The Pure Sound remained completely ‘clean’ and transparent sounding throughout. It manages to add a touch of ‘life’ into the proceedings, but without ever seeming to add any colouration or distortion. Against some of the very best (but at insance prices) it lacks some of the final edge of definition, but nevertheless misses nothing you’d want to hear. It is one of those rare components that seem to breathe some life into music, but without sacrificing accuracy or adding anything unecessary. Against some top-end solid-state equipment, the Pure Sound gives nothing away, yet does seem to increase the sound stage a little, certainly in width. Piano and woodwind in particular (always a difficuly feat) are rendered superbly and with a sense of reality that is quite startling. My treasured vinyl copy of Keith Jarrett’s Koln Concerto was brought to vibrant life, with all the energy and beauty of the recording perfectly portrayed.
Highly musical, ultimately listenable and (size apart) perfectly practical, this should be right at the top of the shopping list for anyone considering one of the last steps to musical nirvana. £5000 is a lot of money for a pre-mplifier in the real world, but I would genuinely call it a bargain.
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