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Designer Peter Lau empowers the buyer with the opportunity to customize the final voicing of the product. In its simplest form, you are dealing with four different preamplifiers here, each with its own sonic characteristics. The added option of tube choices in different stages plus the prospect of tube rolling opens up a world of quite unlimited possibilities. For this evaluation, I limited the choices to four and remained with the stock tubes lest the variables become unmanageable.


Anode out combined with low feedback creates the greatest midrange immediacy with a huge cushion of air. To achieve this, it gives up some image specificity as well as extreme low-bass definition and some mid-bass dynamics. Vocals are illuminated and quite convincing.

Adding feedback increased focus especially in the high frequencies, offered a flatter response and improved bass definition. There was some loss of that massive cushion of air but it became more proportional across the spectrum and image specificity was more accurate. The cathode follower output with low feedback had similar characteristics to that of anode/high feedback but a slightly different tonal balance. Adding feedback to it gave very tight focus and flat response but was the driest of the configurations and also the dynamically most polite.

In my system, the best match was the anode output with generally the higher feedback setting. A different system will yield different results to underscore Mr. Lau’s purpose for the flexibility of Audio Reference 2S which can achieve optimum matching over a wide variety of systems and tastes. Next I broke down the sound into its component parts.


Noise: The Reference 2S was extremely quiet without hum or hiss. The inherent vulnerability of the 300B to microphonics in low-level circuits was never evident to suggest that its resonance control provisions were effective. Individuals who prefer considerably louder levels might be able to incite the problem but for me the preamplifier exhibited a very low noise floor and performed flawlessly.


Dynamics and resolution: The Reference 2S had good overall perceived dynamic range although it did compress on an absolute basis. It demonstrated excellent prowess in the mid and surrounding bands where the ear is most sensitive. The dynamic characteristics could be varied by selecting different output and feedback settings. In low feedback/anode mode, there was some minor politeness in the midbass due to a corresponding frequency elevation in the midrange. Dynamic compression occurred at both the micro and macro ends of scale but remained unobtrusive.


On the loud end, the preamp’s lack of grain and its very low noise floor coupled with inherently good tube clipping kept things detailed, articulate and sweet without serious penalties. Perceived distortion was exceptionally low and there was never any indication of distress on challenging material. With instruments and massed vocals, there was a strong perception of a rise in pressure as opposed to loudness especially in the high frequencies  The eardrum was driven to distortion rather than the music, i.e. much like a live performance.



The compression at the low end of the scale was almost unnoticeable due to the extremely low noise floor. It raised low- level information to a threshold where it fell within the dynamic capabilities of a wider range of systems and replaced 'dead air' with a rich wash of relevant ambient information. Low-level detail such as the drawing of breath, instrumental flourishes, emotional nuance, crowd noises and hall information were all more pronounced and more relevant to the performance.


Dynamic contrasts on the micro scale were well preserved, subtle detail and texture occurring in a vivid and convincing manner. Macro dynamics and fast transients were presented with good texture and definition but some mild loss of hard edge and absolute contrast. The performance was strongest in the midrange where it was extremely natural and engaging. Overall resolution was quite good and enhanced by the raised dynamic floor. Subtle shadings and details were all more apparent with instruments exhibiting their unique texture and hall space being clearly defined. The preamplifier easily differentiated instruments from their hall reverberation indicating a good separation of intricate timing information.


Frequency response - high frequencies. There was a remarkable lack of grain. The preamp had excellent perceived extension, sweetness, transient snap and texture all at once. The sweetness was the hallmark and this machine never sounded dry, strained or harsh. A curiosity was that a note could be harsh or dissonant but that the instrument creating it could maintain a sweetness of natural character.  This is something one hears in a live performance but rarely in reproduced music.



Midrange. One would expect a tube preamp of this caliber to shine here and Mr. Lau’s creation did not disappoint. It delivered vocals and instruments that were authentic and palpable to an exemplary degree. Their aliveness was quite seductive and demanded that the music be listened to. The preamp walked the tightrope of tonal transparency and dimensionality by slightly favoring dimensionality and in the process affording the midrange realistic body. 'Natural' is the correct term here.


Bass had extremely good detail, power and authority with only a minor loss of absolute articulation in the lowest regions of subwoofer territory. It did maintain proportion at all levels and acoustic instruments were presented with realistic warmth and without exaggeration. The bass never drew attention to itself but rather highlighted the character of the instruments. Taken on a whole, the virtues of the midrange extended up and down the scale and maintained a thoroughly convincing illusion of real people and real instruments wherever the recording could deliver it. There was a mild warmth to the overall frequency balance without euphonic indulgence. The character still fell within the bounds of neutral.


Soundstaging and imaging: The soundstage was mildly forward but depth was proportionally correct. Width was good and dimensionality was a strong suit. The preamplifier emphasized solidity of objects as opposed to absolute transparency, presenting life-sized and lifelike images in convincing fashion. Specificity and focus were very good and there was natural separation of individual musical lines. Hall acoustic and dimension were believable. Air was intrinsic to the event rather than a separate item. There was an aliveness to much of the reproduced material which went beyond artifice and could often fool the ear into mistaking reproduction for the live event.


Following the microscopic analysis, the question still remained - what did the Reference 2S sound like? The short answer is extremely good. There was a cohesiveness to the presentation which kept instrumental size and timbre highly believable and allowed them to maintain character over their frequency spectrum at all dynamic levels. People and instruments simply sounded more real over a wider range of recordings. While this preamp can be bettered in some areas of dynamics and definition of hard edges, the Audio Space Reference 2S has the ability to get out of the way of the music and often disappear. There were moments when the electronic chain evaporated and the illusion of live music replaced it. The original Audio Space Reference 2 gained a reputation for sounding more like a live event and less like an electronic reproduction. It would appear that the S version retained that capability.


Does that illusion make the preamp more accurate or euphonic? That presents an interesting philosophical argument. In a bypass test, I concluded that it is most certainly additive. One could argue that any deviation in this respect is an exercise in euphonics. I would counter argue that the preceding chain itself was flawed and that the Reference 2S restored the perception of more information, thus making it more authentic to the original event. Make no mistake, whatever exactly Mr. Lau has accomplished here is no simple parlor trick. Accurate or euphonic? Take your pick but the illusion is utterly convincing.



Conclusion: Has Mr. Lau succeeded in meeting the expectations placed on this product? Yes and probably in excess. The Audio Space Reference 2S is of sufficient caliber that it could easily have been introduced at a premiere piece. Mr. Lau’s estimates that the Reference 2S will deliver 90% of the performance of the Reference 2 in unbalanced mode so the price/performance level here is quite staggering.


Does it have weakness? Of course. Any design regardless of price is a balance between capabilities and tradeoffs and it will always be up to the reader to decide which compromises they can live with. It is accurate enough to appeal to the numbers crowd and emotionally engaging enough to appeal to the heart. The preamp finds the music and weaves a convincing illusion of reality where the recording will allow.


Is this the preamp for you? If you are partial to tubes and don’t need a balanced circuit or  integral phono stage, it's well worth considering. If you desire the flexibility to custom-tailor the sound, your degree of option here is unprecedented. If you’ve had your eye on the bigger Reference 2 and found its sound appealing but the price tag out of reach, this new model will be very tempting. If you like your sound bold, three-dimensional and visceral, it's a strong performer.


It’s built like a 40lb tank and build quality is top notch. The sound quality approaches the company’s own best work at a fraction of the cost. If Audio Space is unfamiliar to you, it would make a very worthwhile detour to give the Reference 2S a listen. All in all,  it's a preamp that merits serious consideration. I took my own advice—and that of my wife—and we acquired the review sample for our system. Our days without a dedicated preamp are no more.

Quality of packing: Double shipping box. Product is well protected with a generous quantity of formed foam. Individual components including tubes are separately protected in their own foam sleeves.
Reusability of packing: Yes.
Condition of components received: Perfect.
Delivery: Hand-delivered by the Canadian distributor of Charisma Audio.
Website comments: Well laid out. Informative.
Human interactions: Professional and friendly.
Warranty: 2 years part and labor,. 6 months on the tubes.   
Final comments & suggestions: This is a preamp that honors the music in recordings without emphasizing the flaws. This 'no preamp' listener was certainly most impressed.

Audio Space website
Canadian importer's website