# Accuphase P 5000 Brochure

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## Extracted text from Accuphase P 5000 Brochure (Ocr-read)

### Page 1

Stereo power amplifier is ideal match for C-2400 MCS technology in input stage improves S/N ratio, distortion ratings and other characteristics. 6 pairs of wide-band high-power transistors in parallel push-pull configuration for each channel. Massive 1 kVA toroidal power transformer supports 650 watts of power into ultra-low 1-ohm impedance. 4-step gain control effectively reduces noise. The P-5000 continues the distinguished design policy of the M-8000 and P-7000. This stereo power amplifier uses carefully selected top quality parts throughout and is an ideal match for the C-2400 preamplifier. MCS topology in the input stage reduces noise even further. Refined technology and inspired design result in superb performance and flawless 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 these design goals, a power supply that fully meets the demands of the output stage is necessary. In the output stage of the P-5000, six pairs of high-power transistors with a rated collector dissipation of 150 watts are arranged in a parallel push-pull configuration for each channel. The devices are mounted to large heat sinks for efficient dissipation of thermal energy. Rated output power into 1 ohm is 650 watts per channel (music signals only). Power remains linear also when impedance changes, as exemplified by the rating of 400 watts into 2 ohms, 200 watts into 4 ohms and 100 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-5000 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. The important input stage also has been given due attention. Another Accuphase innovation called MCS (Multiple Circuit Summing) helps to minimize noise. Current feedback topology assures totally stable operation up to very high frequencies. Balanced inputs shut out external noise. The copper foil side of the PCBs and all input and output terminals and major signal carrying points are gold plated, for enhanced signal purity. BIAS STABILIZER CIRCUIT BIAS STABILIZER CIRCUITBIAS STABILIZER CIRCUIT 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 660 watts. At 2 ohms, the figure is 500 watts, at 4 ohms 310 watts, and at 8 ohms 171 watts. This demonstrates the impressive performance reserves of this amplifier. 6-parallel push-pull power unit delivers guaranteed linear power output of 400 watts into 2 ohms, 200 watts into 4 ohms and 100 watts into 8 ohms The output stage uses high-power transistors with a rated collector dissipation of 150 watts and collector current of 15 amperes. These devices boast excellent frequency response, current amplification linearity, and switching characteristics. The transistors are arranged in a 6-parallel push-pull configuration (Figure 1) for ultra-low impedance and mounted on a massive heat sink made from diecast aluminum. This assures effective heat dissipation and reduces the impedance of the output stage. Power linearity is maintained down to ultra-low loads, which demonstrates the impressive capabilities of this amplifier.MCS topology in input stage reduces residual noise and drastically improves S/N ratio The input stage features Accuphase's original MCS (Multiple Circuit Summing) design. Three separate unit amplifiers for the input signal are connected in parallel, minimizing noise and distortion and greatly improving other performance parameters as well. This approach yields further improved sound quality. NFB switching type gain control reduces residual noise Because the current feedback type amplifier circuitry is very stable and introduces little phase shift, an NFB switching gain control has become possible (MAX, –3 dB, –6 dB, –12 dB). With this approach, reducing gain also results in reduced noise. This is especially beneficial when using highly efficient speaker systems where the noise floor could be a problem. Fig. 2 Output power vs. load impedance(output voltage/output current: actual measurements) * 1-ohm operation possible with music signals only Output voltage (V) Output current (A) Fig. 1 Circuit diagram of amplifier section (one channel)

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Current feedback circuit topology prevents phase shifts in high frequency range The P-5000 employs the renowned current feed- back principle developed by Accuphase. At the sens- ing point of the feedback loop, the impedance is kept low and current detection is performed. An impedance-converting amplifier then turns the cur- rent into a voltage to be used as the feedbacksignal. Since the impedance at the current feed- back point (cur- rent adder in Figure 3) is very low, there is almost no phase shift. Phase com- pensation can be kept to a minimum, re- sulting in excel- lent transient response and superb sonic transpar- ency. 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-5000 features a massive toroidal power trans- former with a maximum rating of 1 kVA. The trans- former is housed in a non-resonant alu- minum case filled with a material that transmits heat and absorbs vibrations. This completely pre- vents any adverse influences on other circuit parts. A tor- oidal transformer uses heavy-gauge copper wiring on a doughnut-shaped core, resulting in low impedance and high efficiency while allowing compact dimensions. Two ul- tra-large aluminum electrolytic capaci- tors rated for 47,000 µF each serve to smooth out the pulsating direct current from the rectifier, providing more than ample filter- ing capacity. n nn n nPower amplifier assembly with 6 parallel push- pull transistor pairs per channel mounted directly to large aluminum diecast heat sinks, MCS circuitry, and current feedback amplifier Fig. 4 Frequency response with current feedback I-V converter Current NFB network Amplifier Output Trans-impedance amplifier Current adder – Input Buffer + Input Buffer Fig. 3 Current feedback amplifier principle diagram