Tisbury Audio Mini Passive Preamplifier II

15.02.2016..
Tisbury Audio Mini Passive Preamplifier II
Tisbury Audio Mini Passive Preamplifier II

Oscar Wilde once said: “I continue to amaze me. It's the only thing that makes my life worth living”. This aphorism can certainly be applied to all aspects of life, also to that which, in my opinion, represents an undeniable factor, that is to say, the love for music and the equipment to reproduce it, otherwise conventionally known as High Fidelity. The desire to amaze me … is he – it is not a mistake, to me “he” is a friend! – who still pushes me to buy a record only because I am inspired by the cover, and again, is “he” who convinces me to haunt unknown musicians' gigs in the hope of listening to a new talent. Likewise, in a quite distressing setting of large-scale Hi-End manufacturing/distribution, it is always the search for the extraordinary, which makes me move among small design realities hoping to find a real, substantial, appliance able to make a system properly sound and not just make it work. The Tisbury Audio Mini Passive Preamplifier II belongs, no doubt, to the first type and, at the same time, represents a micro-reality in the audio scene, so aware and proud to be so as to call themselves a small and enthusiastic firm based in London. Also the offer of products is quite slim, but with the advantage that they are handcrafted in situ and sold directly on the premises so as to be able to drastically lower the price while maintaining the quality high.

 

The passive-preamp type is one that keeps to trigger heated arguments among fundamentalist audiophile factions, in particular about the dualism between active and passive preamplifier systems, namely about the supremacy of one or the other. As it happens for the countless antagonisms that exist in Hi-Fi, e.g. analogue v. digital, the dispute is totally fruitless and does not make any worthwhile contribution to the movement. Let us leave absolutism to Thomas Hobbes. I adore vinyl, but have a house full of CD’s and, certainly, not as decorative objects. Any situation that would be privileged, analogue or digital, tubes or transistors, active or passive preamps will have to face the canonical pros and cons, even though some advantages are actual and irrefutable.

As regards passive preamplifiers, the main advantage is that you do not need feeding, avoiding so, at the source, all the possible problems linked to the passage of electricity from the power supply network, i.e. noise and harmonic and intermodular distortion. Last, but not least the advantage of being able to reach significant levels of stereo separation.

The active preamp is a component, which contains circuits that can amplify the level of line tensions as well as the gain unit. The latter is nothing else that the signal level as it enters the inputs of the preamplifier. An active preamplifier can use tubes, transistors or operational systems as gain devices. A passive preamplifier does not use gain devices. It can be equipped with transformers or other impedance-matching devices, but cannot amplify a line-signal level.

A possible issue that could arise from the use of a passive preamp is an impedance misalignment, with negative consequences on dynamics and speed, albeit a conditional event. This type of electronics shifts the signal-guide responsibility directly on the line stages of the source. If our source is not able to handle a proper level of signal for a long path, consequently needing a strengthening of the gain unity, a passive preamp is perfectly useless.

However, we must not make the usual mistake of considering a passive preamplifier as a simple volume control subject to a fluctuating sound output. The resistor-based volume controls turn up the impedance so that the control should be followed by an active stage in order to reduce it.

The active stage, be it tube or transistor based, is the place where every amplifier creates its peculiar sound. The truth is that no active stage can ever be considered neutral, for its personal character will have to interact synergistically also with the characters of the other audio-system components. Synergy, together with volume control and input selection, forms the trinity of the fundamental functions of a preamp. Should it lack in neutrality, synergy will be compromised at every change of components, forcing the user to replace other elements of the chain or even the preamp itself. Having analysed these aspects, every audiophile shall be free to make its laic choices, according to their own sensibility without starting useless wars of religion.

In orienting the choice, not negligible is the design factor of the current sources that, differently from those of ten or so years ago, produce a very high output volume. For this reason, the matching with an active preamp will result in lowering instead of increasing the power of the signal, while a passive preamp, with the exception of some transformer-coupled models – which manage to obtain an amplification in tension – turns out to be extremely efficient in keeping under control a signal that, being subjected to an increase, could cause some audio shocks.

Obviously, the addition of a passive preamp into an audio system should be always made keeping the input/output impedance values well in mind. The source, in most cases, does not disdain a high input impedance, while the final amplifier appreciates low output values. A passive resistor preamp does not operate this way, on the contrary, to the attenuation of the output impedance will correspond an increase in output impedance. For which reason, it will be important to know the electrical specifications of the upstream and downstream components of the preamp as well as the cables that will have to be carefully taken into account also in terms of size, avoiding excessive length.

 

This technical parenthesis, besides aiming to stimulate the detailed study and the knowledge of the electrical dynamics of the interfaces, means to communicate loud and clear that the choice of a passive preamp is not for all tastes and all seasons. To every passive preamp should correspond an audiophile active [Editor’s Note: - Pun intended! ;-)] or at least conscious of the system he/she intends to make. If he/she were one of those who live of sterile charts and reason in terms of a particular brand that is better than another, which, in turn, is still superior to another one and, poor thing, has not been able to acquire any critical independence, he/she would better give up.

The Mini Passive Preamplifier Tisbury Audio – let me quote Ex. Editor Castelli – is something for the refined palates. To begin with, it is coherent with the fundamental features of a device of that kind: simplicity and minimalism. What can be simpler than a volume control and a switch? What is more minimal than an anodised aluminium body of really reduced size with an elegant black walnut facia? But if you look just below the surface, discreet, but because of that more captivating, the small Tisbury is a great example of rationalism of space.

 

Two small polished/shiny knobs are situated on the wooden facia, one for volume control, the other, 3-stepped, for channel selection. Passing by the small sides, with parallel engraved lines, one reaches the small back panel – in the presence of this small object it comes very natural to use all those diminutives – of the chassis, where are symmetrically positioned as many as 5 pairs of RCA terminals, 3 functioning as inputs and the remaining 2 as outputs, all rigorously gold plated. Notwithstanding its plainness and the absence of refined elements, the mini preamp has an operative heart that promotes it to the High-End class. If need be, further control sections are situated under the base of the enclosure. By a set of mini switches, accessible via 4 round holes, it is possible to select the function of the second output by choosing the positions Off, Loop (which allows you to hook up to a second amplifier), and Variable (that is active and changeable, exactly like its twin). The remaining section is devoted to the attenuation field and this is Tisbury's distinctive feature, which differentiate it from the passive-preamp multitude. The deamplification range can be set at 0, -10 and -20 dB. This ample flexibility allows you to widen the range of possible matching by considerably reducing dangers of impedance mismatching with other electronic devices of the system. In order to further enhance this feature, Tisbury have designed their mini pre amp with a stated impedance equal to zero at full volume, minimising possible side effects aka roll-off and saturation. Volume control is set through a system of thin-film SMD (Surface Mounting Device) resistors, connected in series like on rails, moving along which the output level changes, exactly as it happens in stepped potentiometers. Such mechanism affects the general device quality in terms of longer life, very low noise, channel balance and constant impedance along the whole operation range. But is the sound quality, which no doubt marks out our tiny device, converting it into a superb music machine. Tisbury Audio can be positioned with excellent results both between source and final amplifier or as an interface between active preamp and final power amplifier, mostly if one wishes to set up an "imperfect bi-amplifier" audio system. I hope co-ex editor Rocchi will not be offended if I like to consider this review as the ideal appendix to his splendid article Shootout Test | Eleven Passive Preamps with Transformers, that has appeared on ReMusic some time ago. This because the Mini Passive Preamplifier II, though not transformer-coupled, expresses itself in similar modes and can be tested mostly for what concerns essential parameters such as low frequency control, accurate audio image re-creation and tone colour, a triad that notoriously coincides with the characteristics more sharply criticised by those who disparage this kind of electronic devices.

The number of record used in the test was limited to 2. Limited so to speak, if you consider that the artistic density and the musical content of both are second to none. I am speaking of Ry Cooder's Jazz and Hans Theessink's Slow Train both in vinyl and CD.

The attribute that indelibly brands Tisbury's character is its absolute transparency. This feature was somehow expected given that it is universally known that clarity is directly related to the absence of active components along the signal path. But transparency creates the conditions for bringing out music details, allowing subtler sound nuances. I perceived a great sense of rhythm, given that the relationship of duration in the sequence of sounds reveals itself harmoniously, let me say that the cadence of transient attack and decay is sensational for a "little one" like our preamp. Physicality is certainly not one of the best traits of bass, but control and speed are its suitable substitution. On the other hand, mid and treble show a massive presence and the latter surfaces really smooth and soft. Tonal expression is very natural so that one does not get tired also after extensive listening. Tisbury proves to be devoid of acoustic sycophancy or dynamic sham of any kind and does not care to show off at all. On the contrary, it helps us understand the actual recording level by behaving mercilessly with shoddy ones. The image cannot certainly be considered very ample, but well recreated and distributed into space. Signal compression never appears and a pleasant sense of airiness is revealed. These evident specifications, allow you a certain operating space, to the extent that playing with cables different for conductivity, resistance, capacity and size, one can affect the sound profile, modelling it according to one's inclination, taking care to comply with the initial recommendations concerning electrical balances.

 

The Tisbury Audio Mini Passive Preamplifier II has been tested on my system taking the place of my Audio Tekne transformer-coupled preamp. It would not be believable if I said that it behaved on the same level. But I can honestly testify that its performance was extremely respectable, keeping the quality level of my household listening high, with flashes of class I would never have thought I could obtain from an object with a price as Lilliputian as its size. But as Dostoevsky said “… it's always for the little things that you lose your head”. I am so enthusiastic of this discreet electronic device, which was able to amaze me where millionaire counterparts did not manage to. I hope this test can be the occasion to start a virtuous course of revaluation of passive preamps, ostracised because of the usual indolence of the stubbornly arrogant and "sequined" world of Hi-End, as regards experimentation and deep knowledge of pure and genuine high fidelity. And if it were combined with a sound affordability, so much the better.

Highly recommended.

 

 

Official technical specifications

Enclosure: Handmade American black walnut facia and anodised aluminium body, laser engraved markings

Attenuator: 1% tolerance thin film SMD resistors, ±0.25dB channel balance at all levels, gold plated contacts

Size: 105mm x 60mmx150mm WxHxD

Input Impedance: 10kOhms

Output Impedance (at full volume): 0 ohms

Fixed Attenuation: 0dB, -10dB, -20dB. Set by switches on base

Power Supply: None (it's passive!)

Number of Inputs: 3

Number of Outputs: 2

Output 1: Variable - level set by volume control

Output 2: Variable or Loop, set by switches on base:

Variable: Level set by volume control simultaneously with Output 1. Provides a second main output for connecting another amplifier, active subwoofer etc. 
Loop: Bypasses the volume control. Use this to loop out to a headphone amp or other device without adjusting the volume. 

 

Official distributor: to Tisbury Audio website

Official current UK price: 129.00 pounds, 167.00 EUR

Associated equipment: to Giuseppe "MinGius" Trotto's system

 

 

Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
View of the Upper Part of the Tisbury Audio Mini Passive Preamplifier Board ...
View of the Upper Part of the Tisbury Audio Mini Passive Preamplifier Board ...
...and its bottom
...and its bottom
Photo courtesy of Tisbury Audio
Photo courtesy of Tisbury Audio
by Giuseppe Trotto
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