INTEGRATED STEREO AMPLIFIER E-407 - Accuphase

1 INTEGRATED STEREO AMPLIFIERE-407m triple parallel push - pull output stage delivers quality power: 180 watts 2 into 8ohms m Current feedback principle combines superb sound with total operation stabilitym Logic-controlled relays for shortest signal paths m Separator switch allowsindependent use of pre/power sections m Large toroidal power transformer m Balancedinputs m Option board available for playback of analog recordsState-of-the-art INTEGRATED AMPLIFIER features current feedback topologyfor superb high-range phase fidelity. Wide-range power transistors intriple parallel push - pull configuration and massive toroidal transformerdeliver ample power: 260 watts 2 into 4 ohms, 180 watts 2 into 8ohms. Option board enables analog record reproduction in E-407 represents a new pinnacle of ampli-fier design.

2 Featuring latest technology and us-ing only the highest quality materials, this inte-grated STEREO AMPLIFIER is destined to become anew reference. Frequency response, S/N ratio,and all other performance aspects make theE-407 perfectly suited for the new generationof ultra high quality program sources such asSACD and INTEGRATED AMPLIFIER provides various advan-tages such as convenient operation and modestspace 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 thispossibility, the E-407 is designed to achieve totalelectrical and structural separation of thepreamplifier and power AMPLIFIER sections. Thesetwo parts operate as if they were entirely sepa-rate components.

3 A switch even allows using thepreamplifier and power AMPLIFIER 's highly acclaimed current feedbacktopology virtually eliminates phase shifts in theupper frequency range and assures outstandingperformance 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 powersupply section which features a massive, highlyefficient toroidal power transformer housed in adiecast enclosure equipped with heat the standard configuration, the E-407 has sixinputs, two of which employ the balanced princi-ple that assures ideal signal transmission char-acteristics. Provisions for two tape recorders, witheasy dubbing in both directions, tone controls, andloudness compensation are further attractive fea-tures.

4 An optional analog disc input board allowsreproduction of analog records with outstandingsonic external design of the E-407 continues theAccuphase tradition, featuring a champagne goldbrushed front panel. Two large power meters inthe 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 theE-407 is a great addition to any living parallel push - pull output stage deliversquality power: 260 watts/channel into 4 ohms,220 watts/channel into 6 ohms or 180 watts/channel into 8 ohmsThe 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, andswitching performance characteristics. They areconnected in a triple parallel configuration (Fig-ure 1) for low impedance and mounted directlyon a large heatsink to assure ef-ficient dissipationof thermal allows the E-407 to deliver am-ple power output ,amounting to 260watts into 4 ohms,220 watts into 6 ohms, or 180 watts into 8 ohmsper feedback topology in power amplifierand preamplifier sections guarantees top-level performanceIn the E-407 , the signal current rather than thevoltage is used for feedback.

5 Figure 2 shows theoperating principle of this circuit. At the sensingpoint of the feedback loop, the impedance is keptlow and current detection is performed. An im-pedance-converting AMPLIFIER then converts thecurrent into a voltage to be used as the feedbacksignal. 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 transientresponse andsuperb 3 showsfrequency re-sponse for dif-ferent gain set-tings of the cur-rent feedbackamplifier. The graphs demonstrate that responseremains uniform over a wide line AMPLIFIER for superior sonicpurityThe line AMPLIFIER is entirely built from discreteparts, to assure optimum performance. Using aprinciple developed by Accuphase , a differentialpure complementary push - pull circuit is combinedwith a single-ended push - pull emitter followeroutput stage .

6 This comparatively simple topologyreduces the need for phase compensation, re-sulting in effortless, utterly natural and transpar-ent reliable logic-controlled relaysProgram source switching is performed by logic-controlled relays which are arranged so as topermit theshortest possi-ble signalpaths. Thehermeticallysealed relaysare high-qual-ity types devel-oped specifi-cally for de-manding com-munication ap-plications. The contacts are twin crossbar typesplated with gold for minimum contact resistanceand outstanding long-term controls use summing active filters forpure soundThe tone control circuitry 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 transistorsRelays connected directly togold-plated input/ output jacksFigure 2 Principle of current feedback amplifierFigure 1 Circuit diagram of power AMPLIFIER section (one channel)Figure 3 Frequency response with current feedback(Response remains uniform also when gain changes)Line AMPLIFIER assembly withcurrent feedback circuitry Biasstabilizercuit.

7 The flat signal is passedstraight through, and only whenan adjustment is required, thecharacteris-tics createdat F1 and F2are added tothe signal,thereby pro-ducing thedesiredchange. Thisdesign pro-vides efficientcontrol with-out degrading signal toroidal power transformer and high fil-tering capacityThe power supply section is a critical aspect ofany power AMPLIFIER . The E-407 features a largetoroidal power transformer with a rating of 600VA. The transformer is housed in a non-resonantaluminum enclosure filled with damping materialthat has excellent heat transfer transformers which use heavy-gaugecopper wiring on a ring-shaped core have vari-ous advantages, such as very low impedance,small size, and high conversion efficiency. Thetoroidal type transformer used by Accuphase isideally suited for audio applications.

8 It has the fol-lowing characteristics:aNear-circular core caliber allows near-circularcoil windings with high packing density, result-ing in low leakage flux and minimum ferrite core diameter and copperwindings with high specific gravity mean lowferrite losses and low inrush massive electrolytic capacitors, each ratedfor 33,000 uF assure ample reserves also for re-production of the most demanding headphone AMPLIFIER for best soundThe E-407 provides a separateamplifier for the phone jack de-signed to provide superior sonicperformance. The speaker out-put can be cut off by a switch,and the main volume controlcan be used to adjust theheadphone listening sets of heavy-dutyspeaker terminalsThe oversize speakerterminals are made ofextruded high-puritybrass material whichaccept also heavy-gauge speaker cable.

9 Two setsof outputs with aspeaker selectorare provided, andbi-wiring (supply-ing the same sig-nal via dual leadsto speakers withseparate high-fre-quency and low-frequency inputs)is also analog peak power metersThe power meters use logarithmic compressionto cover a wide dynamic range, letting you easilymonitor the output level of the rapidly fluctuatingmusic signal. Meter illumination can be switchedoff, which is conven-ient for example ina home remote commander RC-20 Allows volume control and sourceswitchingPower amplifierassembly with tri-ple parallel push - pull output devicesmounted to largeheat sink and cur-rent feedback am-plifier circuitryHeavy-duty speaker terminalsFigure 4 Tone control circuit principle(Summing active filter type)Massive filtering capacitors andlarge toroidal power transformerGUARANTEED SPECIFICATIONS[Guaranteed specifications are measured according to EIA standard RS-490.]

10 ]mContinuous Average output Power (both channels driven, 20 - 20,000 Hz)260 watts per channel into 4 ohms220 watts per channel into 6 ohms180 watts per channel into 8 ohmsmTotal Harmonic Distortion (both channels driven, 20 - 20,000 Hz) , with 4 to 16 ohms loadmIntermodulation ResponseHIGH LEVEL INPUT/MAIN INPUT20 - 20,000 Hz +0, dB (for rated output )2 - 150,000 Hz +0, dB (for 1 watt output )mDamping Factor120 (with 8-ohm load, 50 Hz)mInput Sensitivity, Input ImpedanceSensitivity For rated outputFor 1 W output (EIA)HIGH LEVEL INPUT158 mV mV20 kWBALANCED INPUT158 mV mV40 kWMAIN INPUT V 112 mV20 kWmOutput Voltage, output ImpedancePRE output : V, 50 ohms(at rated continuous average output )mGainMAIN INPUT output : 28 dBHIGH LEVEL INPUT PRE output : 20 dBmTone ControlsTurnover frequency and adjustment rangeBASS: 300 Hz 10 dB (50 Hz)TREBLE: 3 kHz 10 dB (20 kHz)mLoudness Compensation+6 dB (100 Hz), (Volume control setting -30 dB)mSignal-to-Noise Ratio (input-converted noise) Input shorted, IHF-A weighting S/N ratio at rated inputHIGH LEVEL INPUT113 dB 82 dBBALANCED INPUT 92 dB 82 dBMAIN INPUT128 dB 103 dBmPower Level MetersS/N ratio (EIA) Logarithmic compression, peak readingmetersdB scalemLoad Impedance4 - 16 ohmsmStereo HeadphonesSuitable impedance.