Accuphase E 550 Brochure

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The ultimate integrated pure class A amplifier – Power MOS-FETs arranged in triple parallel push-pull configuration. Innovative AAVA volume control. Strong power supply with large toroidal transformer and high filtering capacity supports linear output progression of 120 watts/ch into 2 ohms, 60 watts/ch into 4 ohms, or 30 watts/ch into 8 ohms. Power amp section uses current feedback for optimum high-frequency phase characteristics and MCS+ topology. The first integrated pure class A amplifier from Accuphase, the E-530, drew a lot of attention and praise. The E-550 now takes over as a further improved and fully redesigned successor model. It stands at the pinnacle of integrated amplifiers, featuring latest technology and strictly selected high-quality parts. For the first time in an integrated amplifier, it offers the revolutionary AAVA type volume control. In AAVA, amplification and volume control are fully unified, and no variable resistors are used. This ensures excellent sound quality and performance, but the circuitry requires aconsiderable amount of space. In order to enable the use of AAVA in an integrated amplifier, advanced design know-how and mounting technology were brought into play, to increase component density while keeping sonic purity and performance at the high level that is the hallmark of Accuphase. The result speaks for itself. The power amplifier section features the highly acclaimed current feedback principle developed by Accuphase, as well as further improved MCS+ circuit topology, for even better electrical characteristics. The output stage devices arepower MOS-FETs famous for their musical qualities, arranged in a triple parallel push-pull configuration and driven in pure class A. Low output impedance and constant voltage drive ensure superb speaker control. The large high- efficiency toroidal transformer (430 VA) in the power supply, along with eight 10,000 µF filtering capacitors selected for their sonic properties support linear progression of output regardless of impedance, with a per-channel rating of 120 watts into 2 ohms, 60 watts into 4 ohms, or 30 watts into 8 ohms. BUFFER V- I Converter CPU OUTPUT INPUT I -V Converter Volume Balance Attenuator AAVA (Accuphase Analog Vari-gain Amplifier) volume control ■ ■■ ■ ■Volume control resolution AAVA adjusts the listening volume by means of 16 current switches which are operated by 16 weighted V-I conver ter amplifiers. The number of possible volume steps set by the combination of these converter amplifiers is 2 to the power of 16 = 65,536. ■ ■■ ■ ■AAVA maintains high S/N ratio and uniform frequency response With conventional volume controls, the impedance increases significantly at settings that correspond to normal listening levels, thereby leading to increased noise. Because AAVA performs adjustment by selective use of V-I converter amplifiers (changing the actual gain), there is no change in impedance and thus no deterioration of S/N ratio or alteration of frequency response. Changing the volume with AAVA does not mean introducing noise or detracting from the high performance of the amplifier. ■ ■■ ■ ■Same operation feel as a conventional high-quality volume control The volume control knob position is detected by a dedicated CPU which in turn selects the current switches for AAVA operation. Operating the knob therefore feels exactly the same as with a conventional control, and as before, operation via the remote commander is also possible.■ ■■ ■ ■Simple circuit configuration AAVA unifies the amplifier and volume control functions, resulting in a circuit that is electrically very simple. Long-term reliability is excellent, with performance and sound quality that will remain unchanged also after prolonged use. ■ ■■ ■ ■AAVA means analog processing The AAVA circuit converts the music signal from a voltage into a current, switches gain by means of current switches, and then reconverts the current into a voltage. The entire process is carried out in the analog domain. ■ ■■ ■ ■No more left/right tracking differences or crosstalk Because AAVA is an electronic circuit employing highly precise metal film resistors, there is virtually no left/right tracking error also at low volume levels. Since channels can be kept separate, crosstalk also does not present a problem. ■ ■■ ■ ■Attenuator and balance control also implemented by AAVA The functions of the attenuator and the left/right balance control are covered by the AAVA circuit as well, eliminating the need for additional circuit stages. Keeping the configuration simple helps to maintain high performance and sonic purity. Input music signal 16 current switches (65,536 possible combinations) Conversion into current with 16 weighting stages (1/2 - 1/2 16)CPU detects position of volume knob and operates current on/off switches according to knob positionVolume knob is turned and position is detected Reconversion of current into voltage Current values are added The newly developed volume control called AAVA (Accuphase Analog Vari-gain Amplifier) is totally different from conventional controls using resistors. Because the music signal does not pass through variable resistors, it is not affected by changes in impedance. This means that high signal-to-noise ratio and low distortion of the signal are maintained. Adjusting the volume does not introduce any deterioration in sound quality. ■ ■■ ■ ■AAVA control assembly with three AAVA units and CPU arranged neatly on a mother- board AAVA operates by feeding the music signal to a V-I (voltage - current) converting amplifier where it is weighted in 16 steps [1/2, 1/2 2, ... 1/2 15, 1/2 16]. 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 voltage by an I-V (current - voltage) converter. AAVA operation ■ ■■ ■ ■Output amplifi e triple p power M mount e sink