Accuphase P 3000 Brochure
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0 10 20 0 8 16 24 32 40 400W 330W 220W 133W71W 1Ω 2Ω 4Ω 8Ω 16Ω Output current (A) Output voltage (V) Note 1 Low amplifier output impedanceWhen forming the load of a power amplifier, a loudspeaker generates a counterelectromotive force that can flow back into the amplifier via the NF loop. This phenomenon is influenced by fluctuations in speaker impedance and interferes with the drive performance of the amplifier. The output impedance of a power amplifier should therefore be made as low as possible by using output devices with high current capability. This absorbs the counterelectromotive force generated by the voice coil and prevents the occurrence of intermodulation distortion. Note 2 Constant drive voltage principleEven when the impedance of a load fluctuates drastically, the ideal power amplifier should deliver a constant voltage signal to the load. Figure 2 is a graph plotting the output voltage versus current characteristics. Even when the load changes, the output voltage remains almost constant, showing linear current progression. Actual measurement of clipping power at the extremely low load impedance of 1 ohm yields 400 watts. At 2 ohms, the figure is 330 watts, at 4 ohms 220 watts, and at 8 ohms 133 watts. This demonstrates the impressive performance reserves of this amplifier. Fig. 2 Load impedance vs. output power (Output voltage/output current) ★1 ohm rating is for music signals only. Power amplifier with instrumentation amp configuration The P-3000 features a new "instrumentation amplifier" principle whereby 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 vir tually shut out. The result A stereo power amplifier capable of delivering 400 watts into 1 ohm (with music signals) Fully balanced signal paths as found in high-quality instrumentation amplifiers. Further refined MCS+ topology and current feedback design. Improved S/N ratio, minimal distortion, and great performance in all other areas. Power supply with massive 700 VA toroidal transformer and triple parallel push-pull arrangement of high-power transistors in each channel. The P-3000 is based on the same design technology as the renowned P-7000 and P-5000 models. Using only carefully selected top quality parts throughout, the P-3000 is an ideal match for the C-2000 preamplifier. A new feature in the P-3000 is the fact that all signal paths from the input terminals onwards are fully balanced, an approach otherwise found only in instrumentation amplifiers of the highest quality. In addition, the power amplifier section employs an improved version of MCS called MCS+ (Multiple Circuit Summing plus), as well as the famous Accuphase current feedback topology. S/N ratio, distortion, and other electrical characteristics are further improved. And of course, these refinements manifest themselves in even better sound quality. In order to drive any kind of speaker with precision and authority, a power amplifier must provide extremely low output impedance (Note 1) and be capable of supplying a constant drive voltage at all times (Note 2). To realize constant-voltage capability over the entire frequency range, a powerful output stage supported by a capable power supply are necessary. In the output stage of the P-3000, three pairs of high-power transistors are arranged in a parallel push-pull configuration for each channel. The devices are mounted to large heat sinks on both sides for efficient dissipation of thermal energy. Rated output power into an ultra-low impedance of 1 ohm is 400 watts per channel (music signals only). Power remains linear also when impedance changes, as exemplified by the rating of 300 watts into 2 ohms, 150 watts into 4 ohms and 75 watts into 8 ohms. Even speakers with very low impedance or with drastic impedance fluctuations can be driven effortlessly and accurately. By using the P-3000 in bridged mode, it is possible to create a monophonic amplifier with even higher power reserves. This performance is sustained by a massive high-efficiency Super Ring toroidal transformer and large filtering capacitors. OUTPUT + B3 – B3 –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 Q24 Q25 Q26 Q13 Q11 Q15 Q10 Q14 Q12 Q16 NFB NETWORK MCS+Multiple Circuit Summing( ) Bias stabilizer circuit Bias stabilizer circuit Bias stabilizer circuit Bias stabilizer circuitBias stabilizer circuit Fig. 1 Circuit diagram of amplifier section (one channel) + – –INPUT NFB NETWORK GAIN CONTROL CIRCUIT NFB NETWORK OUTPUT +INPUT + – + – is a drastic improvement in operation stability and reliability. Further refined MCS+ topology Accuphase's original MCS (Multiple Circuit Summing) principle uses a number of identical circuits connected in parallel to achieve superior performance characteristics. The MCS+ is a further refined version of this approach. Improvements in the bias circuitry of the input-stage buffer amplifier result in greater stability. This in turn makes it possible to extend the parallel operation approach to the class-A drive stage of the current/voltage converter, thereby further lowering the noise floor. Triple parallel push-pull power unit delivers guaranteed linear power output of 300 watts into 2 ohms, 150 watts into 4 ohms, and 75 watts into 8 ohms The output stage uses high-power transistors with a rated collector dissipation of 130 watts. These devices feature excellent frequency response, current amplification linearity, and switching characteristics. The transistors are arranged in a triple parallel push- pull configuration and mounted on a massive heat sink. This assures Instrumentation amplifier configuration Signal input stage Power amplifier stage
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effective heat dissipation and reduces the impedance of the output stage. Current feedback circuit topology prevents phase shifts in high frequency range The P-3000 employs the renowned current feedback principle developed by Accuphase. At the sensing point of the feedback loop, the impedance is kept low and current detection is performed. An impedance-converting amplifier then turns the current into a voltage to be used as the feedback signal. Since the impedance at the current feedback point (current adder in Figure 3) is very low, there is almost no phase shift. Phase compensation can be kept to a minimum, resulting in excellent transient response and superb sonic transparency. Minimal amounts of NFB are used to maximum effect, providing natural energy response. Figure 4 shows frequency response for different gain settings of the current feedback amplifier. The graphs demonstrate that response remains uniform over a wide range. Robust power supply with "Super Ring" toroidal transformer and high filtering capacity The P-3000 features a massive toroidal power transformer with a maximum rating of 700 VA. The transformer is housed in a case filled with a material that transmits heat and absorbs vibrations. This Gain(Large) (High) Frequency completely prevents any adverse influences on other circuit parts. A toroidal transformer uses heavy-gauge copper wiring on a doughnut-shaped core, resulting in low impedance and high efficiency while allowing compact dimensions, which is especially useful for audio appli- cations. Two ultra-large aluminum electrolytic capacitors rated for 47,000 µF each serve to smooth out the pulsating direct current from the rectifier, providing more than ample filtering capacity. BufferCurrent adder I-V converter Trans-impedance amplifier Amplifier Output Current NFB network – Input Buffer + Input Fig. 3 Principle of current feedback amplifier nPower amplifier assembly with 3 parallel push-pull transistor pairs per channel mounted directly to large heat sink, MCS+ circuitry, and current feedback amplifier Fig. 4 Frequency response with current feedback(Response remains uniform also when gain changes)