Accuphase A 46 Brochure

Page 1

Trans-impedance amplifier Amplifier Output (+) input bufferCurrent adder (-) input buffer Current NFB network /V NFB NETWORK NFB NETWORK NFB NETWORK OUTPUT ´
INPUT µ
INPUT Signal input stage Power amplifier stage ´µ ´µ ´µ Instrumentation amplifier OUTPUT Bias stabilizer circuit -“INPUT +INPUT NFB NETWORK NFB NETWORK GAIN CONTROL CIRCUIT + -“ -“ + REGULATOR REGULATOR + B1 -“ B1 -“ B2 + B2 Q1 Q3 Q2 Q4 Q8 Q6 Q7 Q5 Q9 Q17 Q19 Q18 Q20 Q21 Q22 Q23 Q25 Q27 Q29 Q24 Q26 Q28 Q30 Q31 Q32 Q13 Q1 1 Q15 Q10 Q14 Q12 Q16 NFB NETWORK Bias stabilizer circuit Bias stabilizer circuit Bias stabilizer circuit Bias stabilizer circuit Gain control MCS+ (Multiple Circuit Summing) Power MOS-FETs 6-parallel push-pull Output current (A) Output voltage (V) Ã’
1-ohm operation possible with music signals only converter Principle of current feedback amplifier Instrumentation amplifier configuration Ù Figure 1 Circuit diagram of amplifier section (one channel) Parts selected for sound quality and reliability Meter circuitry assembly Power MOS-FETs Filtering capacitors Toroidal power transformer Line/balanced input connectors Large speaker terminals Gain selector Meter selector MOS-FET switches Input selector Protection circuitry Figure 2 Load impedance vs. output power (output voltage/output current) Power amplifier assembly with six parallel push-pull power MOS-FET pairs per channel mounted directly to large heat sink, MCS+ circuitry, and current feedback amplifier. Instrumentation amplifier and further refined MCS+ topology Phase selector for balanced input Ã- Ã- Pure Class A power amplifier with power M\fS-F\bT devices -“ Fully balanced signal paths realized through instrumentation amplifier configuration. Further refined MCS+ topology and current feedback result in superb sound quality and excellent ratings for S/N ratio, THD, and other parameters. Strong power supply and power M\fS-F\bT devices in six-parallel push-pull configuration sustain an amazing 360 watts per channel into ultra-low impedance 1-ohm loads (with music signals). 4-step gain control provides flexibility. Pure Class A power amplifiers from Accuphase have long been blending the purity of class A operation with the superior performance of power MOS-FETs. Acclaimed by audiophiles the world over, these products reflect a level of technical know-how that is second to none. Each model in the A-65/A-45/A-35 lineup has received high praise, both for sound quality and performance. The A-46 is a minor-change successor to the A-45, positioned as the medium power level model of the series. Naturally, the A-46 also demonstrates the same unwavering dedication to sound quality and outstanding design policy which are the hallmark of Accuphase. This pure class A stereo power amplifier with its distinctive external heat sinks is built for the true enjoyment of music. The A-46 uses latest instrumentation amplifier topology throughout, which allows fully balanced transmission in all signal handling stages. The power amplifier section features further improved MCS+ topology and the renowned current feedback approach. This results in electrical characteristics that surpass even the demanding standards set by its predecessors. Employing only highest grade materials and strictly selected parts, the A-46 realizes very low output impedance which ensures that constant drive voltage is available for the speakers. The output stage features power MOS-FETs renowned for their excellent sound and superior reliability. For each channel, six of these devices are arranged in a parallel push-pull class A arrangement. MOS-FETs have excellent frequency response characteristics and high input impedance, which reduces the load of the preceding (drive) stage. Driving these devices in pure class A means that constant power is always supplied, regardless of the presence or absence of a musical signal. This makes the amplifier completely immune to external influences and ensures stable operation at all times. The large heat sinks mounted on the outside reliably prevent internal heat buildup, allowing the amplifier to sustain output levels of as much as 360 watts per channel into 1 ohm (with music signals). If even higher power is required, bridged mode turns the A-46 into a high-grade monophonic power amplifier. Ù Power modules with 6-parallel push-pull arrangement of power MOS-FETs deliver a guaranteed linear output of 360 watts per channel into 1 ohm (music signals only), 180 watts into 2 ohms, 90 watts into 4 ohms, or 45 watts into 8 ohms. Ù Amply dimensioned power supply with high-efficiency toroidal transformer and two large 47,000 µF filtering capacitors. Ù Bridged mode allows upgrading to monophonic amplifier with 720 watts into 2 ohms (music signals only), 360 watts into 4 ohms, or 180 watts into 8 ohms. Ù Revised NFB design minimizes output impedance and increases damping factor, resulting in further improved sound quality. Ù Fully balanced input stage shuts out external noise interference. Ù Mode selector for easy switching between dual mono/stereo/bridged operation Ù Front panel input type selector (line/balanced). Ù 4-step gain control (MAX, -3 dB, -6 dB, -12 dB) minimizes residual noise. Ù Large analog power meters with operation/illumination and sensitivity selector. Ù Speaker protection uses semiconductor (MOS-FET) switch. Elimination of mechanical switches assures long-term reliability and improved signal purity, resulting in further improved sound quality. Ù PCB copper foil and all major signal path components are gold- plated. Ù Two sets of speaker outputs, with large terminals that accept also Y lugs. Instrumentation amp configuration allows fully balanced signal paths The advanced instrumentation amplifier principle used in the A-46 ensures that all signal paths from the inputs to the power amp stage are fully balanced. This results in excellent CMRR (common mode rejection ratio) and minimal distortion. Another significant advantage is that external noise and other external influences are virtually shut out. The result is a drastic improvement in operation stability and reliability. Further refined MCS+ topology for even lower noise Accuphase's original MCS (Multiple Circuit Summing) configuration uses a number of identical circuits connected in parallel to achieve superior performance characteristics. MCS+ is a further refined version of this approach. By extending parallel operation to the class-A drive stage of the current/voltage converter, the noise floor has been lowered further. Current feedback principle assures excellent phase characteristics in high range As shown in the illustration, the A-46 uses the output signal current rather than voltage for feedback. Since the impedance at the current feedback point is very low, there is almost no phase shift. A minimal amount of NFB therefore results in maximum improvement of circuit parameters. In the factory default condition, the switch is set to the left side ("pin e +"), as shown in the illustration. If the balanced output of the connected preamplifier has a "pin w +" arrangement, the switch should be set to the right side.

Page 2

Trans-impedance amplifier Amplifier Output (+) input bufferCurrent adder (-) input buffer Current NFB network /V NFB NETWORK NFB NETWORK NFB NETWORK OUTPUT ´
INPUT µ
INPUT Signal input stage Power amplifier stage ´µ ´µ ´µ Instrumentation amplifier OUTPUT Bias stabilizer circuit -“INPUT +INPUT NFB NETWORK NFB NETWORK GAIN CONTROL CIRCUIT + -“ -“ + REGULATOR REGULATOR + B1 -“ B1 -“ B2 + B2 Q1 Q3 Q2 Q4 Q8 Q6 Q7 Q5 Q9 Q17 Q19 Q18 Q20 Q21 Q22 Q23 Q25 Q27 Q29 Q24 Q26 Q28 Q30 Q31 Q32 Q13 Q1 1 Q15 Q10 Q14 Q12 Q16 NFB NETWORK Bias stabilizer circuit Bias stabilizer circuit Bias stabilizer circuit Bias stabilizer circuit Gain control MCS+ (Multiple Circuit Summing) Power MOS-FETs 6-parallel push-pull Output current (A) Output voltage (V) Ã’
1-ohm operation possible with music signals only converter Principle of current feedback amplifier Instrumentation amplifier configuration Ù Figure 1 Circuit diagram of amplifier section (one channel) Parts selected for sound quality and reliability Meter circuitry assembly Power MOS-FETs Filtering capacitors Toroidal power transformer Line/balanced input connectors Large speaker terminals Gain selector Meter selector MOS-FET switches Input selector Protection circuitry Figure 2 Load impedance vs. output power (output voltage/output current) Power amplifier assembly with six parallel push-pull power MOS-FET pairs per channel mounted directly to large heat sink, MCS+ circuitry, and current feedback amplifier. Instrumentation amplifier and further refined MCS+ topology Phase selector for balanced input Ã- Ã- Pure Class A power amplifier with power M\fS-F\bT devices -“ Fully balanced signal paths realized through instrumentation amplifier configuration. Further refined MCS+ topology and current feedback result in superb sound quality and excellent ratings for S/N ratio, THD, and other parameters. Strong power supply and power M\fS-F\bT devices in six-parallel push-pull configuration sustain an amazing 360 watts per channel into ultra-low impedance 1-ohm loads (with music signals). 4-step gain control provides flexibility. Pure Class A power amplifiers from Accuphase have long been blending the purity of class A operation with the superior performance of power MOS-FETs. Acclaimed by audiophiles the world over, these products reflect a level of technical know-how that is second to none. Each model in the A-65/A-45/A-35 lineup has received high praise, both for sound quality and performance. The A-46 is a minor-change successor to the A-45, positioned as the medium power level model of the series. Naturally, the A-46 also demonstrates the same unwavering dedication to sound quality and outstanding design policy which are the hallmark of Accuphase. This pure class A stereo power amplifier with its distinctive external heat sinks is built for the true enjoyment of music. The A-46 uses latest instrumentation amplifier topology throughout, which allows fully balanced transmission in all signal handling stages. The power amplifier section features further improved MCS+ topology and the renowned current feedback approach. This results in electrical characteristics that surpass even the demanding standards set by its predecessors. Employing only highest grade materials and strictly selected parts, the A-46 realizes very low output impedance which ensures that constant drive voltage is available for the speakers. The output stage features power MOS-FETs renowned for their excellent sound and superior reliability. For each channel, six of these devices are arranged in a parallel push-pull class A arrangement. MOS-FETs have excellent frequency response characteristics and high input impedance, which reduces the load of the preceding (drive) stage. Driving these devices in pure class A means that constant power is always supplied, regardless of the presence or absence of a musical signal. This makes the amplifier completely immune to external influences and ensures stable operation at all times. The large heat sinks mounted on the outside reliably prevent internal heat buildup, allowing the amplifier to sustain output levels of as much as 360 watts per channel into 1 ohm (with music signals). If even higher power is required, bridged mode turns the A-46 into a high-grade monophonic power amplifier. Ù Power modules with 6-parallel push-pull arrangement of power MOS-FETs deliver a guaranteed linear output of 360 watts per channel into 1 ohm (music signals only), 180 watts into 2 ohms, 90 watts into 4 ohms, or 45 watts into 8 ohms. Ù Amply dimensioned power supply with high-efficiency toroidal transformer and two large 47,000 µF filtering capacitors. Ù Bridged mode allows upgrading to monophonic amplifier with 720 watts into 2 ohms (music signals only), 360 watts into 4 ohms, or 180 watts into 8 ohms. Ù Revised NFB design minimizes output impedance and increases damping factor, resulting in further improved sound quality. Ù Fully balanced input stage shuts out external noise interference. Ù Mode selector for easy switching between dual mono/stereo/bridged operation Ù Front panel input type selector (line/balanced). Ù 4-step gain control (MAX, -3 dB, -6 dB, -12 dB) minimizes residual noise. Ù Large analog power meters with operation/illumination and sensitivity selector. Ù Speaker protection uses semiconductor (MOS-FET) switch. Elimination of mechanical switches assures long-term reliability and improved signal purity, resulting in further improved sound quality. Ù PCB copper foil and all major signal path components are gold- plated. Ù Two sets of speaker outputs, with large terminals that accept also Y lugs. Instrumentation amp configuration allows fully balanced signal paths The advanced instrumentation amplifier principle used in the A-46 ensures that all signal paths from the inputs to the power amp stage are fully balanced. This results in excellent CMRR (common mode rejection ratio) and minimal distortion. Another significant advantage is that external noise and other external influences are virtually shut out. The result is a drastic improvement in operation stability and reliability. Further refined MCS+ topology for even lower noise Accuphase's original MCS (Multiple Circuit Summing) configuration uses a number of identical circuits connected in parallel to achieve superior performance characteristics. MCS+ is a further refined version of this approach. By extending parallel operation to the class-A drive stage of the current/voltage converter, the noise floor has been lowered further. Current feedback principle assures excellent phase characteristics in high range As shown in the illustration, the A-46 uses the output signal current rather than voltage for feedback. Since the impedance at the current feedback point is very low, there is almost no phase shift. A minimal amount of NFB therefore results in maximum improvement of circuit parameters. In the factory default condition, the switch is set to the left side ("pin e +"), as shown in the illustration. If the balanced output of the connected preamplifier has a "pin w +" arrangement, the switch should be set to the right side.