Accuphase A 35 Brochure

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Accuphase A 35 Brochure

Extracted text from Accuphase A 35 Brochure (Ocr-read)


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n Triple push-pull arrangement of power MOS-FETs delivers 150 watts per channel into 1 ohm (music signals), 120 watts into 2 ohms, 60 watts into 4 ohms, or 30 watts into 8 ohms. n Strong power supply with large transformer and high fi ltering capacity. The power supply features a large high-effi ciency transformer and two 47,000 μF aluminum electrolytic capacitors selected for sound quality. n Instrumentation amplifi er principle allows fully balanced signal paths, and current feedback amplifi er topology drastically improves S/N ratio. n Bridged mode supports upgrading to monophonic amplifi er with 300 watts into 2 ohms (music signals), 240 watts into 4 ohms, or 120 watts into 8 ohms. Simply by setting the mode selector to the bridged position, the A-35 is turned into a monophonic amplifi er with 4 times the output power as compared to stereo operation. This can be used when more power reserves are needed. n Redesigned NFB circuit path results in minimized output impedance, thereby further improving the damping factor. This manifests itself in even better sound quality. n Analog power meters with off/sensitivity selector. Meter illumination and operation as well as meter sensitivity (0 dB, -20 dB) can be controlled with a selector. n 4-step gain control also minimizes residual noise.The gain control switches gain in the fi rst instrumentation amplifi er stage. Four settings are available: MAX, -3 dB, -6 dB, -12 dB. n Fully balanced input stage shuts out external noise interference. n Mode selector with dual mono position supports bi-amping. n Oversize speaker terminals accept also Y lugs. A pure class A amplifi er maintains a constant current fl ow regardless of the presence or absence of a musical sig- nal. This makes it possible to create a perfectly stable sound stage with unparalleled ambience that is the dream of any audiophile. Within this rarefi ed breed of amplifi ers, the high-end pure class A stereo amplifi er A-65 has gar- nered praise the world over as the ultimate reference for superb performance and sheer sonic excellence. The A-35 was developed as a successor to the A-30 while inherit- ing many design aspects of the A-65. Dedication to the best sound possible is always an Accuphase hallmark. The use of the instrumentation amplifi er principle allows fully balanced input signal paths, and further refi ned MCS+ topology pushes noise and distortion down to absolutely minimal levels. In terms of its design as well as its sound, the A-35 offers a highly attractive entry point to the world of pure class A. In the output stage of the A-35, proven power MOS-FET devices are used in a triple-parallel confi guration for each channel. MOS-FETs have excellent frequency character- istics, and their high input impedance reduces the load imposed on the preceding drive stage. The devices are directly mounted on large heat sinks for effi cient dissipa- tion of thermal energy, assuring perfect operation stabil- ity. Driving these devices in pure class A produces rich, high-defi nition sound that brings out the fi nest nuances in the music. The power supply of an amplifi er is its ultimate source of energy. Unless it provides ample reserves, sound quality will suffer, and even basic performance parameters may not be met. The A-35 has a massive power transformer and two 47,000 μF smoothing capacitors specially select- ed for their sonic properties. This sustains an output power rating of 120 watts into 2 ohms, 60 watts into 4 ohms, or 30 watts into 8 ohms per channel, and it enables the A-35 to perfectly handle even very-low impedance speakers or speakers with wildly fl uctuating impedance characteristics. To prevent clipping on occasional momentary high-level pulses, the maximum clipping level of the A-35 is set to 50 watts per channel into 8 ohms (sine wave output). Use in bridged mode is also possible, turning the A-35 into a high- power monophonic amplifi er. Pure Class A sound that-s every audiophile-s dream - Input stage features ful- ly balanced signal paths as found in high-quality instrumentation ampli ers. Further re ned MCS+ topology and current feedback result in superb sound quality and outstanding S/N ratio and other performance parameters. Strong power supply section and power MOS-FET devices in triple-parallel push- pull con guration sustain linear power output progression down to ultra-low impedances, with the capability to deliver 150 watts into 1 ohm (music signal). INPUT Figure 1 Circuit diagram of amplifi er section (one channel) Gain selector Power transformer Bias stabilizer NFB NETWORK Protection and power meter circuit assemblyFiltering capacitors Unbalanced and balanced input connectors NFB NETWORK GAIN CONTROL CIRCUIT Bias stabilizer Bias stabilizer Bias stabilizerNFB NETWORK REGULATORREGULATOR INPUT MCS+ (MultipleCircuit Summing) Gain control3-parallel push-pull power MOS-FETs Output voltage (V) Output current (A) Figure 2 Load impedance vs. output power (output voltage/output current) > 1-ohm operation possible with music signals only OUTPUT Bias stabilizer Meter selector Large speaker terminals High-reliability parts selected for sound quality Instrumentation amplifi er NFB NETWORK SPEAKER TERMINALS

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n Power amplifi er assemblyPower amplifi er assembly with three parallel push-pull power MOS-FET pairs per channel mounted directly to large heat sink, MCS+ circuitry, and current feedback amplifi er. Current feedback principle assures excellent phase characteristics in high range As shown in the illustration, the A-35 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. INPUT OUTPUT INPUT Current NFB network I/V converter Current adder Trans-impedance amplifi er Amp- lifi er Principle of current feedback amplifi er Buffer Buffer Instrumentation amp confi guration allows fully balanced signal paths The newly adopted -instrumentation amplifi er- principle 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 signifi cant advantage is the fact that external noise and other external infl uences are virtually shut out. The result is a power amplifi er with drastically improved operation stability and reliability. Further refined MCS+ topology reduces noise even further Accuphase-s original MCS (Multiple Circuit Summing) principle uses a number of identical circuits connected in parallel to achieve superior performance characteristics. MCS+ is a further refi ned version of this approach. By extending parallel operation to the class A drive stage of the current/voltage converter, the noise fl oor has been further lowered. INPUT NFB NETWORK GAIN CONTROL CIRCUIT INPUT NFB NETWORK Signal input stage Power amplifi er stage OUTPUT Instrumentation amplifi er confi guration Instrumentation amplifi er and further refi ned MCS+ topology