Accuphase E 350 Brochure
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+ – Integrated amplifi er with innovative AAVA-II volume control - Instrumenta- tion amplifi er confi guration in power amplifi er section allows balanced signal transmission. Current feedback design ensures optimal high-range character- istics. High-power transistors in parallel push-pull arrangement are supported by ample power supply with massive transformer and large fi ltering capacitors. The result is an abundance of quality power: 100 watts per channel into 8 ohms. n CPU assembly for control of AAVA-II and various functions INPUT V- I ConverterVolume Balance AttenuatorI-V Converter OUTPUT CPU AMP. Feedback network AAVA-II operation principle AAVA-II (Accuphase Analog Vari-gain Amplifi er) is a novel volume control concept that completely does away with variable resistors in the signal path. Because the music signal does not have to pass through such devices, there is no adverse infl uence from changes in impedance. This means that the outstanding S/N ratio and low distortion of the amplifi er are not compromised in any way, and the same superb sound quality will be obtained at any volume setting. AAVA-II (Accuphase Analog Vari-gain Amplifi er) type volume control n AAVA-II input stage employs current feedback principle that ensures high-speed, low-noise operation and assures excellent characteristics at high output voltages. n Volume control resolutionThe listening volume is adjusted by a combination of 16 V-I converters. The number of possible volume steps is 2 to the power of 16 = 65,536, as determined by current switches. n AAVA-II circuitry is deceptively simpleBecause AAVA-II employs circuitry that is electrically very simple, long-term reliability is excellent, with n AAVA-II maintains high S/N ratio and uniform frequency response Because AAVA-II does not introduce any change in impedance, there is no deterioration of S/N ratio or alteration of frequency response. Changing the volume with AAVA does not mean introducing noise or otherwise degrading the sound quality of the amplifi er. n Control knob gives same operation feel as with a conventional high-quality volume control. n Attenuator and balance control also implemented by AAVA-II performance and sound quality that will remain unchanged also after prolonged use. n AAVA-II means analog processingThe AAVA-II circuit converts the music signal from a voltage into a current, to allow control by current switches, and then back into a voltage. The entire process is carried out in the analog domain. n No more left/right tracking differences or crosstalk Because AAVA-II is an electronic circuit employing only fi xed-value resistors, there is virtually no left/right tracking error also at low volume levels, and crosstalk also does not present a problem. The acclaimed E-300 series has a strong following among discerning music lovers and plays a central role in the Accuphase integrated amplifier lineup. Technological excellence is a common theme, and know-how is inherited and further enhanced throughout the series. The E-350 represents a full model change from the model E-308. Featuring the revolutionary AAVA-II (Accuphase Analog Vari-gain Amplifi er) volume control, the E-350 combines latest technological sophistication with high-grade parts and materials, resulting in an integrated amplifi er capable of bringing out the fi nest nuances in any music source. The AAVA principle was introduced to high acclaim in the model E-550, adding another highlight to the roster of Accuphase audio innovations. The E-350 now features a further refi ned version of this revolutionary circuit. While AAVA in its initial form required a considerable amount of physical space, AAVA-II delivers the same peerless performance in a more compact form factor. This was made possible by implementing highly sophisticated surface mount technology while increasing component density and integration as well as optimizing the layout. The power amplifi er section is confi gured as an advanced instrumentation amplifi er, which enables fully balanced signal transmission throughout. In conjunction with the current feedback principle, this makes for even better electrical characteristics. The output stage uses high-power transistors designed for audio applications arranged in a parallel push-pull confi guration, greatly improving the capability of the amplifi er to drive low impedance loads. Speaker operation is sustained by a large power transformer and amply dimensioned fi ltering capacitors, allowing the amplifi er to deliver plenty of quality power: 2 × 140 watts into 4 ohms or 2 × 100 watts into 8 ohms. Current feedback amplifi er How AAVA-II works AAVA-II operates by feeding the music signal to a V-I (voltage - current) converting amplifi er where it is weighted in 16 steps [1/2, 1/4, ..., 1/32,768, 1/65,536]. The 16 current steps are turned on or off by 16 current switches, and the combination of switch settings determines the overall volume. The switching operation is controlled by a CPU according to the position of the volume control knob. The combined signal current forms a variable gain circuit that adjusts the volume. Finally, the combined current is converted back into a music signal voltage by an I-V (current- voltage) converter. 16 current switches (65,536 possible combinations) Conversion into current with 16 weighting stages (1/2~1/2 16)Volume knob is turned and position is detected Reconversion of current into voltage Current values are added CPU detects position of volume knob and operates current on/off switches according to knob position n AAVA-II volume control assembly with higher integration density of components and circuitry
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n Power amplifi er assembly with parallel push-pull devices mounted to large heat sink and current feedback circuitry INPUT NFB network NFB networkNFB networkOUTPUT Circuit diagram of E-350 power amplifi er (one channel) Bias stabilizer Bias stabilizer Bias stabilizer n Output stage is confi gured with high-power transistors in parallel push-pull confi gu- ration, delivering high-quality power: 140 W/4 ohms or 100 W/8 ohms per channel. High-power transistors Large power transformer Large-size speaker terminals Input/output connectors directly linked to relays MC/MM button EXT PRE button n Instrumentation amplifi er principle in power amplifi er section works in tandem with current feedback design, for outstanding high-range phase characteristics. n Logic-controlled relays for signal switching ensure high sound qual- ity and long-term reliability. n Balanced input connectors shut out external noise interference. n High Carbon cast iron insulator feet further enhance sonic purity. n Supplied remote commander RC-200 Allows volume adjust- ment and input source switching. n Power supply features mas- sive high-effi ciency 550 VA transformer and two large fi ltering capacitors (22,000 µF × 2) n Analog peak power meters. n Option board installation slots. Filtering capacitors n Two sets of large-size speaker terminals suitable for Y lugs. n E-350 front panel switching enables MC/MM selection for optional Analog Disc Input Board AD-20. n EXT PRE button and pream- plifi er output/power ampli- fi er input connectors allow independent use of pream- plifi er and power amplifi er sections.