INTRODUCTION
	BACKGROUND & DESIGN PHILOSOPHY
	TECHNICAL OVERVIEW
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	REVIEWS

Phase 6 Preamplifier     Phase 2 Reference Integrated   Phase 3 Reference Power Amplifier   Phase 1 Reference Dual-mono Amplifier

Shearne Audio   For the discerning music lover who prefers the beautiful and involving mid-range of tube amplification and also wants the reliability and bass control of solid state, Shearne Audio offers the best of both worlds: an iron fist in a velvet glove. During a ten-year period of design and development, John Shearne, the founder and chief design architect of Shearne Audio, has focused on combining both of these design methodologies to produce the most beautiful-sounding and authoritative solid state electronics currently available. The combination of a rich and involving mid-range with the frequency extension and bass control of solid-state is one of the design goals that differentiate Shearne Audio products from the myriad of "black boxes with knobs" available today, and the optional blue marble or piano black finish options definitely distinguish Shearne Audio products cosmetically. By continuously improving the integration of these two design goals beyond the limits of prior art, John Shearne has created a new paradigm of musical realism and involvement that transports the listening experience to a new level, one that is unobtainable from any other design. Another design goal of Shearne Audio is simplicity, and all products are implemented with a minimalist approach of "straight wire with gain," using the fewest number of parts necessary to achieve the design goals, and built with only the very best components and sub-assemblies available. The result is pure, natural, and open sound with very high reliability: the fewer the number of parts that are used, the fewer the number of things can go wrong which will require servicing. Thus in addition to their unequaled sonic presentation. Shearne Audio products have one of the highest mean time between failure specifications of any consumer electronics products currently available. In order to permit existing owners of Shearne Audio products to benefit from the results of ongoing research and development that are implemented in current production versions throughout the line, all registered owners of Shearne Audio products may have their units upgraded to current production specifications for a nominal fee. In this way the design improvements being made by John Shearne and his team will never render a previous model obsolete, and existing owners never need worry about being left behind, as is the case with too many consumer electronic lines these days. Thank your for taking the time to learn about Shearne Audio. If you have any questions or would like more information, please contact O. S Services, the exclusive North American distributor for Shearne Audio, at your convenience.

PHILOSOPHY Established for more than 10 years now, it has always been the aim of Shearne Audio to provide high quality sounds from simple ideas. This not only keeps the pricing relatively sensible when compared with some of our competitors, but also ensures reliability of our products in general. If a design is simple in execution, there is less to go wrong, and less to get in the way of a customer's enjoyment. We also encourage brand loyalty through the offer of our upgrade service - as individual models are improved through their lifetime, upgrades to latest specification are available at reasonable prices enabling customers to take advantage of significant improvements. BACKGROUND Shearne Audio was founded in 1990 by John Shearne, with the firm belief that a market existed to introduce solid state amplifiers, combining the main strengths of a good valve design, i.e. a clear lucid mid range and sweet treble but with the solidity of bass and reliability of a good transistor, while maintaining sound quality and musicality for extended listening pleasure. Working with a team of Specialist Engineers, renowned within the Hi-Fi industry, John Shearne directed the design of the Phase 1 pre/power combination Amplifier, which was launched in July 1991 to critical acclaim from the UK and International Hi-Fi press. In pursuit of audio excellence, Shearne Audio has a committed policy of developing and applying the latest technological advancements, while maintaining the sound characteristics exclusive to the Award winning Shearne Audio range. Thus the Phase 2 Integrated Amplifier was launched in October 1993, establishing Shearne Audio as a leading manufacturer of some the finest sounding audio equipment available today. In November of 1995, the Phase 3 Reference Power Amplifier was designed for bi-amplification use with the Phase 2 Reference Integrated. An intrinsic part of Shearne Audio's design philosophy is to facilitate provisions for retrofittable upgrades throughout the range and thereby provide customers with a range of audiophile products to suit all pockets while not becoming obsolete through technological advancements. In 1996, the Phase 5 100 watt monoblocks were designed, giving the Shearne Audio range greater versatility for the purist. July 1996 saw the launch of the Phase 6 Pre-Amplifier designed on the strengths on the acclaimed Phase 1, specifically designed to incorporate facilities ideal for the audio visual market. Offering superb sound quality unequalled at its price level. The latest addition to the Shearne Audio range is the Phase 7 CD Player, launched in December 1998. The Phase 7 continues Shearne Audio's design objectives by incorporating the latest technological developments in audio innovation and promising musicality unsurpassed in its price range. John Shearne is currently directing the development of an am/fm tuner and a DAC, which will be available in 2nd or 3rd quarter 2000, as well as some home theater products to be announced. To the potential owner, Shearne Audio is now able to offer a superb range of products, flexibility, affordability and upgradability rarely seen in the Hi-Fi industry today. With the unique blue marble effect finish and the black piano finish, the Shearne Audio range is sure to add grace, style and elegance to any professional or domestic environment, as well as outstanding sound quality.

Shearne Audio TECHNICAL OVERVIEW

Shearne Audio Power Amplifier stages All of the Power Amplifier stages employed in Shearne Audio Products use a circuit topology similar in concept to a basic valve (tube) amplifier, but of course executed in solid state components, thus negating the need for an output transformer. Consequently we have engineered products that have many of the likeable aspects of Valve Amplifiers, such as smooth midrange, delicate treble, and deep rich bass, whilst managing to lose some of the more intrusive aspects of many modern day solid-state designs much of which is caused by very high levels of negative feedback, a feature we have not had to employ in our design, as we employ the simple minimum amount of negative feedback to ensure stability. All units have a damping factors below 40 because of the manner in which negative feedback is applied. The method utilised in these designs is such that by the normal measurement methods, a 0R33 or 0R22 Ohm resistor appears in series with the output. However, although the measured Damping Factor appears low, compared to most competitors products, the audible effect is not noticeable. The power output available into 4 Ohm loads is deliberately limited to ensure the long-term reliability of the products, as due to the circuit topology, and with reference to our opening statements, were this not done, there is the possibility that the output transistors would overheat by current overload. The situation is roughly similar to the requirement of 8 Ohm and 4 Ohm taps on a valve amplifier's output transformer. Since most loudspeakers are represented in the 6 to 8 Ohm impedance category, we have elected to provide maximum power into these loads. Loudspeakers with a very "easy" 4 Ohm rating can still be driven quite satisfactorily, but at a slightly lower output power than that available for a 6 Ohm plus loudspeaker. Although the main power amp circuits have push-pull output stages, it would perhaps be more accurate to refer to the output stage as a pull-push stage. It has been found that this type of configuration is in our opinion a far better system for playing music, but does have one small draw-back, and this is noticeable by the slight "plop" the amplifiers can make when power is first applied to them. This noise is the result of small DC-Offsets settling down at turn-on, and is usually about 1-2 volts presented to the loudspeakers for a fraction of a second - it will do no damage to the loudspeakers, but can be disconcerting to some people. Many of our competitors use relays in the signal path to negate such effects, but after considerable work on this particularly small problem, we have decided that the intrusive effect to sound quality of any circuitry employed to remove this noise, was too much of a deficit to be made up with the removal of the "plop"! Work on this particular issue is still going on, and if we find a suitable solution, it will be applied to future products. People who remove the cover of any of the units will see that we have elected to use Integrated Circuit Chips in the circuit. This is for a very simple reason - they are the best components for the job. Without going into too much detail that may not be in our own interests, although it is quite common knowledge that IC chips do not usually sound as good as discrete circuitry in the field of audio engineering, the manner in which we are using the IC's is quite unusual - it has more of an electronic control function than an audio processing role.... All of our power amp stages are capacitor coupled, with frequency response set for linear operation between about 1Hz and 60kHz. High quality components are used for this function, and this choice was made to negate the need for any kind of the offset servo systems employed by so many - again such systems affect sound quality, and on this subject we will not compromise. Shearne Audio Preamplifier stages All pre-amp stages in the Shearne Audio range employ close tolerance Blue-Velvet Alps potentiometers as the first component in the signal path. These are chosen for their excellent sonic characteristics, and their channel matching at high attenuation levels. Three distinctly different type of Pre-Amp are used throughout our range. Firstly there is the Phase 1 Pre-Amp, which uses once again a circuit topology based upon old valve amplifier ideas. This is a single supply, single-ended, cascode, capacitor coupled class A design, employing high quality components where appropriate, to ensure the best possible fidelity. The optional phonostage is simply a higher gain and equalised version of the same circuit, again using high quality, close tolerance components. The only Integrated Circuits employed are firstly in the Phonostage, where the whole of an LM394 Super-Match pair of transistors are used per channel in the moving coil input stage. The other IC is used in the power supply circuitry, where it is used as part of a configuration to bleed off excess supply current, rather than set up and maintain the supply. The Phase 2 Pre-amp stage is designed to be about as simple as possible. It consists of one FET input Op-Amp IC per channel, with a simple 12dB of gain applied via two resistors. After considerable listening tests, there is no doubt in our opinion that FET units offer the best ultimate sound quality in our units, this being possibly because they allow the simplest circuit configurations to be used, and as we all know - the less processing employed in the signal path - usually the better the results! The resistors used are of quite high values, and together with the choice of an FET Op-Amp, a high input impedance is maintained. A slight drawback to this configuration is that FET Op-Amps are not known for their silence, even though the units employed are "low noise" variants, and together with the high value resistors thermal noise contribution, it is sometimes possible to hear a slight hiss through sensitive loudspeakers. In the Reference version of the Phase 2, a much higher specification IC is used, which is quieter, but at a much higher expense. We believe the compromise made here is valid, in that other (bipolar and quieter) Op-Amps seem to have a detrimental effect on perceived stereo image depth, an effect deemed more serious than a tiny hiss heard when no signal is being played. Hopefully in the future, the noise outputs of FET Op-Amps will improve, and then of course this slight inconvenience will be less apparent. The Phase 2 Phonostage is once again designed to be a simple as possible, but a lot of the more recent ideas in circuit topology have been employed. It consists of two gain stages, separated by a passive R.I.A.A. equaliser. The input stage uses a bipolar low noise Op-Amp, essential in such circumstances, and is configurable in the factory as either Moving Magnet or Moving Coil compatible. The output stage is once again an FET Op-Amp. A DC servo is used to maintain DC offset to below 5mV, but this is configured to be virtually out of circuit above about 0.5Hz. The Phase 6 Pre-Amp uses the third variation of circuit topology in our range. This is a simple Class A, discretely executed differential push pull gain stage, operating from double regulated dual supply lines. It is capacitor coupled at input and output, once again to remove the requirement of "audible" servos. Turn on and user muting are provided, together with fully balanced output facilities, generated through the use of FET Op-Amps. A Class A Headphone driver is available as an option and this is installed such that it only operates when the main outputs are muted, and hence it has no effect on normal pre-amp function. The optional phonostage is switchable via DIP switches for most cartridges of both MM and MC types. This unit uses IC's throughout, but these are carefully selected to ensure optimum performance, phonostages being one area where the high gains available in such devices can be used to good effect. 1) Phase 2 & 3 Reference Power Amplifier Stages Both the Phase 2 Integrated Amplifier and the Phase 3 Power Amplifier employ the same generic power amp electronics and main power supply. The main features of these stages are listed below: a) A 250VA toroidal transformer feeds, via a bridge rectifier, a total reservoir/smoothing capacitance of around 30,000uF, divided equally to positive and negative supply rails. b) All power supply lines on the main PCB are carefully routed to ensure low hum pickup - rather like a three core cable - only wrapped around to fit the main PCB. c) The main supply feeds each channel of the main amp in sequence, and supplies the majority of said stages untreated excepting for a small amount of local capacitance adjacent to the power input of each channel. d) Lower voltage rails are created for each channel through simple Zener regulators, enhanced with wide bandwidth smoothing on each low voltage rail (4.7uF || 470nF) e) The above low voltage rails supply a single operational amplifier and the "tail" of the second stage of the amplifier. f) The signal is terminated to ground at each channels input by a 100K resistor before passing through a 2.2uF Polycarbonate capacitor, where it is terminated to ground again via a 47K resistor. This combination gives the power amp stages an input impedance of about 32K. The signal then passes to the input of an FET operational amplifier configured as an integrator and thus playing a major role in control of open-loop gain. g) The output of the op-amp feeds twin complimentary differential amplifiers - one for positive phase of the signals, the other for the negative phases - i.e. the positive and negative parts of the signal phase are split. h) These twin long tailed pairs then feed a driver stage. i) The output stage comprises a complimentary pair of robust Darlington transistors per channel. Local negative feedback in the power supply lines to these transistors serve to stabilise the output and also current limit the transistors to within their safe operating area. j) Overall negative feedback is taken from the output transistors back to the op-amp at the input, setting the power amplifiers overall gain at X27 (28.7dB) or 740mV for 50W output. k) A zobel network and output inductor are fitted to ensure output stability and rejection of cable borne interference. 2) Phase 2 Reference Pre-Amplifier Stage a) Signals fed in through gold plated PCB mount sockets, passing straight to input selector / record outlet selector. The later is unbuffered, so recording source connected directly to tape outlet via the single record switch. b) The Auxiliary input may be fitted with a phono stage as required. These are supplied for either moving magnet or moving coil cartridges, and each offer high and low gain settings (2.5mV/5mV or 250uV/500uV) - a high specification variant is also now available offering lower noise at high gains. c) The signal passes from the input selector to an Alps "Supapot" volume control, and thence on to a pair of low noise FET input op-amps , connected as X4 (approx) gain blocks. The outputs from these blocks then feed to the pre-amp out sockets on the rear panel, and also of course to the main power amplifier stages described above. d) The Pre-Amp power supply draws its main voltage from the amplifiers main supply. This is zener regulated to +/- 24v and wide bandwidth smoothed, before feeding into +/- 15v IC voltage regulators supplying small reservoir capacitors for the +/- 15v rails for the preamp supply proper. Small local bypass capacitors are fitted across the rails close to the actual pre-amp IC's. This supply also feeds the phono-stage when fitted via a pin header connector. e) Pre-amp DC-Offset is reduced to very small levels through the fitment of small presets local to each op-amp. 3) General Notes Each amplifier is set-up and tested by John Shearne personally. DC-offsets of both pre- and power-amp stages are set via the presets installed, and output stage bias of the power amplifier is set to a within a known range and matched closely on both channels. The "cold" quiescent current running in the output stage is set to between 7 and 12mA, and hence the amplifier may be categorised as "Class B". In normal use, this quiescent current climbs to 20mA or so, and upwards of this if the amplifier is driven hard for long periods. Leaving the units powered up with no signal present will allow the bias to drop to 7 or 8mA on "warmed-up-tick-over" - all ready to go and produce nice sounds, but not sitting there guzzling your electricity supply, serving as a secondary heater. Our advice is that once the units have been installed and powered up for the first time, the power switch should be left well alone, unless you are going on holiday for a few weeks…. 4) Phase 7 Compact Disc Player A new product from Shearne Audio, as with all our products it is designed to make pleasant sounds as its primary goal. Highly advanced technology usually brings with it highly advanced problems to be cured, and for that reason we have designed a product using tried and trusted and understood principles, with possibly just our own slant on the idea…. a) A Far-East sourced OEM transport mechanism and control board are fitted into the chassis. This transport uses the well respected Sanyo laser head, mounted on a sled rather than the swinging arm versions of old. Access times are not as swift as the latest offerings, but the transport is "solid" in its operation. Also supplied with this transport come an LCD display, chosen for its low electronic emissions. The whole mechanism, control PCB and display are supplied with their power from a small separate mains transformer. b) A second larger transformer is fitted to supply our own PCB which contains the DAC circuits and aster Clock. Both of the transformers supply their power to their respective PCBs via a small additional PCB fitted at the rear of the chassis and having a 9-way D-Type socket fitted to the rear panel. This small power supply PCB performs two functions. Firstly the raw AC from both transformers is connected to this PCB, and in the case of the larger (50VA) transformer, bridge rectification and smoothing takes place to provide +/- 20v DC for all the analogue stages of our DAC. A second AC feed is taken from this transformer, rectified via two diodes, smoothed, and then regulated by IC regulator to provide a DC supply for use in the digital supplies required on the DAC PCB. Grounding between these two supplies is via a small RF choke, providing some attenuation of any RF energy that may appear on the digital supply line reaching the analogue ground. The second function of the small PSU PCB is to allow connection of an external (forthcoming) upgraded power supply unit. This will connect to the 9-way D-Type at the rear, and when powered up will activate the relays present on the PSU PCB, disconnecting the existing supply from the circuitry, and allowing the outputs of the new external power supply to feed the main circuitry. c) The 16MHz master clock circuitry on the transport's controller PCB is removed, and a ribbon cable is connected to this PCB to collect or supply the required digital signals to and from this controller. Our main PCB is connected to the other end of this ribbon cable. d) A high specification Master Clock circuit, utilising a Trichord Research 16MHz crystal oscillator module and circuitry similar to the "Clock 2" is executed on our main PCB, supplied with power from the DC supply mentioned above, and then further regulated down to 5v with extensive use if wide band smoothing through use of OSCON solid aluminium capacitors and polycarbonate bypass capacitors. This Master Clock feeds the transport (via the ribbon cable) and also the main DAC circuitry. An additional output feeds a BNC socket on the rear panel, and it is proposed to use this Master Clock output to sync our (forthcoming) external upgrade DAC unit. e) The main PCB has multiple regulation of voltages - +5v for digital and analogue sections, and two +/- 15v supplies, one for each of the two principal analogue stages employed. f) The three principal digital signal coming from the transport section are re-clocked before passing into the Pacific Microsonics HDCD Decoder/Filter IC (PMD100). This is a 8x oversampling digital filter IC, outputting a 20-bit words/samples for each channel. g) The output words from the PMD100 are fed to separate DAC IC's. These are NPC items and are 20-bit multibit stereo DAC IC's . These chips output a balanced voltage signal for each channel. Each IC is then used in complimentary mode and hence two complete stereo DAC IC'' are used to convert the stereo music signal - one IC for each audio channel, giving high levels of linearity and rejection of common mode digital and analogue disturbances. h) The outputs of the DAC IC are converted to single ended and then added through an op-amp in differential mode to give a normal single ended output format. The Analogue Devices OP-42, an FET item, is chosen for its sound quality in this role. i) The audio signal is now processed through a three pole passive low pass filter using quality components, and then into the output buffer stage. j) The output buffer stage is loosely based upon the circuit principles applied in our power amp circuits and Phase 6 Pre-Amp - An FET control op-amp feeds an output driver stage, diode biased into class-A, with overall feedback arrangements completing the circuit. k) Power on/off muting is effected through use of a small relay, allowing the electronics to stabilise their operation points before connecting to the output sockets. l) A standard SP/DIF digital output, buffered and re-clocked, is fitted to the rear panel via a BNC connector. Phase 7 CD Player General Notes: The Phase 7 has been designed to play music and provide pleasure to our customers. Technical specifications are not our principal aim - sound quality is far more important than the Nth degree of technical brilliance…. The Phase 1 Reference Pre and Power Amplifiers These two units are at present the top items in our range. Their price and performance are consistent with the fact that each is totally hand build by the chief engineer alone. The Phase 1 Reference Preamplifier is unusual in that its original concept was to form a circuit based on the operation, nature, and principles of valve (tube) circuits used in this role. This pre-amp uses high quality RCA type input sockets, hand wired direct to the input selector and output recording switch system, then on to an Alps Blue Velvet Potentiometer for volume control, an Alps zero centre-loss balance control achieved by the use of silver plating on the potentiometer tracks, and then on to the twin cascode gain stages, capacitor coupled via high quality polycarbonate capacitors. Twin outputs (for Bi-Amping etc) are fitted, and a switch muting circuit is employed allowing the operating points of the circuit to settle before allowing connection to the power amplifiers - a simple switch in this circuit also allows normal in use muting. (The power up muting circuit has a delay of about 1 minute). The power supply for the Phase 1 Pre-amp is also slightly unusual, in that it draws a constant current from its 50VA transformer, which is then simply regulated and filtered through the act of bleeding excess current supply to ground, whilst supplying a single clean 40v supply rail for the following circuits to use. The Phono stage, when fitted as an option, is switchable for both moving magnet and moving coil pickup cartridges. The MM stage employs a simple cascode input and a driver, followed by passive RIAA EQ, and finally another cascode/driver stage to its output in the input/record switch system. MC is catered for by the addition of a simple head amplifier stage preceeding the MM stage, with loadings and connections being made through separate RCA inputs and a small rear mounted toggle switch. Input sensitivity for line inputs is around 150mV. (A small attenuation is fitted in the CD input line to ensure approximate level with other inputs. Output level for the given input is set between 500mV and 775mV for use with the Phase 1 Power Amplifiers, but can be adjusted to suit almost any other power amp as required. The Phase 1 Reference Power Amplifier is the result of taking the basic Shearne Audio power amplifier circuit topology to its logical conclusion. The unit is dual mono, from the twin power switches onward, with the exception of a simple RF bypass to ground at very high frequencies. The basic circuit concepts used do not differ in any major way from the most basic models in the range, however, there has been major developments in certain areas, together with much higher specification components used in certain crucial places. The power amp circuits themselves use twin paralleled output devices, uprated and quieter driver and signal transistors, high quality polycarbonate input capacitors, and considerably more refined voltage regulation for the input stages. A higher output bias current is allowed to flow through the output stage, the two channels being accurately matched for equality of performance thus ensuring precise imagery. The twin power amp PCBs are mounted to extrusions and external heatsinks to ensure stable thermal operation (the unit takes about ½ an hour to reach ideal temperatures due to this increase of extra metal to warm through, but the wait is worth the inconvenience). Each Amp PCB is then hand wired to their respective power supply capacitors (ALS30's with a total capacitance of 20,000uF per rail, per channel) then back to a 30A bridge and a 330VA toroid for each board. The Phase 1 Power Amplifier, whilst not massively powerful in terms of watts output (around 100Watts) is designed to sound effortless and unforced in the manner of many of the good valve units around, without the physical size, weight, heat, delicacy, and sometimes service requirements of the later. The Phase 1 is able to create deep soundstages, with real bass weight - a powerful sound if you like, without smearing midrange and treble as an expense.

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