Accuphase E 407 Brochure

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Accuphase E 407 Brochure

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State-of-the-art integrated amplifier features current feedback topology for superb high-range phase fidelity. Wide-range power transistors in triple parallel push-pull configuration and massive toroidal transformer deliver ample power: 260 watts × 2 into 4 ohms, 180 watts × 2 into 8 ohms. Option board enables analog record reproduction in top-notch quality. The E-407 represents a new pinnacle of ampli- fier design. Featuring latest technology and us- ing only the highest quality materials, this inte- grated stereo amplifier is destined to become a new reference. Frequency response, S/N ratio, and all other performance aspects make the E-407 perfectly suited for the new generation of ultra high quality program sources such as SACD and DVD-Audio. An integrated amplifier provides various advan- tages such as convenient operation and modest space requirements. However, because its over- all gain is very high, even the slightest interfer- ence or crosstalk at the input can have a consid- erable effect on the sonic result. To preclude this possibility, the E-407 is designed to achieve total electrical and structural separation of the preamplifier and power amplifier sections. These two parts operate as if they were entirely sepa- rate components. A switch even allows using the preamplifier and power amplifier independently. Accuphase's highly acclaimed current feedback topology virtually eliminates phase shifts in the upper frequency range and assures outstanding performance and sound quality. The power am- plifier output stage employs a triple parallel push- pull configuration, using multi-emitter power tran- sistors designed for high-power audio applica- tions. Ample muscle is provided by the power supply section which features a massive, highly efficient toroidal power transformer housed in a diecast enclosure equipped with heat fins. In the standard configuration, the E-407 has six inputs, two of which employ the balanced princi- ple that assures ideal signal transmission char- acteristics. Provisions for two tape recorders, with easy dubbing in both directions, tone controls, and loudness compensation are further attractive fea- tures. An optional analog disc input board allows reproduction of analog records with outstanding sonic quality. The external design of the E-407 continues the Accuphase tradition, featuring a champagne gold brushed front panel. Two large power meters in the center are flanked by the input selector sec- tion and the volume control. Not only by virtue ofits excellent sound, from its looks as well the E-407 is a great addition to any living room. Triple parallel push-pull output stage delivers quality power: 260 watts/channel into 4 ohms, 220 watts/channel into 6 ohms or 180 watts/ channel into 8 ohms The output devices are multi-emitter power tran- sistors designed for high-power audio applica- tions. These devices have excellent frequency re- sponse, forward-current transfer ratio linearity, and switching performance characteristics. They are connected in a triple parallel configuration (Fig- ure 1) for low impedance and mounted directly on a large heat sink to assure ef- ficient dissipation of thermal energy. This allows the E- 407 to deliver am- ple power output, amounting to 260 watts into 4 ohms, 220 watts into 6 ohms, or 180 watts into 8 ohms per channel. Current feedback topology in power amplifier and preamplifier sections guarantees top- level performance In the E-407, the signal current rather than the voltage is used for feedback. Figure 2 shows the operating principle of this circuit. At the sensing point of the feedback loop, the impedance is kept low and current detection is performed. An im- pedance-converting amplifier then converts the current into a voltage to be used as the feedback signal. Since the impedance at the current feed-back point (current adder in Figure 2) is very low, there is almost no phase shift. Phase compensa- tion can be kept to a minimum, resulting in excel- lent transient response and superb sonic transparency. Figure 3 shows frequency re- sponse for dif- ferent gain set- tings of the cur- rent feedback amplifier. The graphs demonstrate that response remains uniform over a wide range. Discrete-type line amplifier for superior sonic purity The line amplifier is entirely built from discrete par ts, to assure optimum performance. Using a principle developed by Accuphase, a differential pure complementary push-pull circuit is combined with a single-ended push-pull emitter follower output stage. This comparatively simple topology reduces the need for phase compensation, re- sulting in effortless, utterly natural and transpar- ent sound. Highly reliable logic-controlled relays Program source switching is performed by logic- controlled relays which are arranged so as to permit the shortest possi- ble signal paths. The her metically sealed relays are high-qual- ity types devel- oped specifi- cally for de- manding com- munication ap- plications. The contacts are twin crossbar types plated with gold for minimum contact resistance and outstanding long-term reliability. Tone controls use summing active filters for pure sound The tone control circuitr y in the E-407 was spe- cially designed with summing active filters. Fig- ure 4 illustrates the operation principle of this cir- High-current power transistors Relays connected directly to gold-plated input/output jacks Figure 2 Principle of current feedback amplifier Figure 1 Circuit diagram of power amplifier section (one channel) Figure 3 Frequency response with current feedback (Response remains unifor m also when gain changes) Line amplifier assembly with current feedback circuitry Bias stabilizer