Accuphase E 250 Brochure

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+ B3 - B3 + - + B2 - B2 - B1 + B1 Q 1 Q 2 Q 4 Q 3 Q 5 Q 9 Q 10 Q 11 Q 12 Q 13 Q 14 Q 7 Q 6 Q 8 + - 10 100 1k 10k 100k 18 16 14 12 10 8 6 4 2 0 2 4- - -6 Unbalanced input/output jacks and balanced input connectors n Parallel push-pull power ampli fi er unit achieves 115 watts per channel into 4 ohms or 90 watts into 8 ohms. The output stage devices feature excellent frequency response, current ampli fi cation linearity, and switching characteristics. These high-power transistors have a rated collector dissipation of 100 watts. n Instrumentation amplifier principle in power ampli fi er section This allows the con fi guration of fully balanced signal paths from the input jacks to the output stage, including the signal input stage. In addition, the current feedback design ensures outstanding high-range phase characteristics. n Large and highly ef fi cient 400 VA transformer and two 22,000 μF fi ltering capacitors selected for sound quality provide ample reserves. n Option board installation slot provides further versatility. With AD-20 board, MC/MM switching on E-250 front panel is possible. n EXT PRE switch and power ampli fi er input connectors allow independent use of power ampli fi er section. n Use of metal thin- fi lm resistors in all signal paths ensures superb low-noise performance. n Large analog power meters show direct power output levels. n Logic-controlled relays for signal switching ensure high sound quality and long-term reliability. n Loudness compensator for enhanced bass at low listening levels n High Carbon cast iron insulator feet further enhance sonic purity. n Versatile array of inputs with balanced connectors to shut out external noise interference. n Two sets of large-size speaker terminals designed for Y lugs. The Accuphase E-200 series of basic integrated ampli fi ers enjoys an excellent reputation both in Japan and on the international stage. The E-250 represents a full model change of the E-213, featuring the new AAVA-II volume control and re fl ecting the latest design technology advances achieved by Accuphase. Carefully selected high- quality materials and parts are used throughout, in order to bring out even the fi nest nuances of the source. Using this integrated ampli fi er af- fords pure musical enjoyment. In the category of integrated ampli fi ers, AAVA implemented in the E-550 and AAVA-II in the E-450 and E-350 have received high praise for being a clearly superior volume control princi- ple. The E-250 inherits this advanced design technology. In order to fi t within the more limited space available, circuitry and component layout have been further re fi ned and advanced integra- tion technology is used to increase mounting density. This was achieved while retaining the outstanding performance that made AAVA and previous AAVA-II implementations such impres- sive feats of technology. AAVA-II in the E-250 of course also completely eliminates variable resistors from the signal path. Ampli fi cation and volume control are integrated in a single entity consisting only of top-quality and highly reliable semiconductor parts. This eliminates mechani- cal wear and associated problems, allowing the control to function perfectly for many years. The power ampli fi er section is con fi gured as an advanced instrumentation ampli fi 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 ap- plications arranged in a parallel push-pull con- fi guration, greatly improving the capability of the ampli fi er to drive low impedance loads. Speaker operation is sustained by a large power trans- former with a maximum rating of 400 VA and amply dimensioned fi ltering capacitors, allowing the ampli fi er to deliver plenty of quality power: 2 × 115 watts into 4 ohms or 2 × 90 watts into 8 ohms. Power ampli fi er inputs and an EXT PRE function let you use the power ampli fi er sepa- rately in a stand-alone con fi guration. Integrated amplifi er with innovative AAVA-II volume control -� In the power am- plifi er stage, high-power transistors in a parallel push-pull arrangement are\ sup- ported by a power supply with massive transformer and large fi ltering capacitors. Experience 90 watts per channel (into 8 ohms) of quality power before \ a perfectly silent background. Instrumentation amplifi er confi guration allows balanced signal transmission. Current feedback design ensures optimal high-range charact\ eristics. INPUT OUTPUT High-power transistors Filtering capacitors Compensator characteristics Large speaker terminals High-reliability parts selected for sound quality Circuit diagram of E-250 power ampli fi er (one channel) MC/MM Selector button Bias stabilizer EXT PRE switch Massive power transformer LOUDNESS COMPENSATOR: ON Frequency in Hz Response in dB Bias stabilizer Bias stabilizer NFB NETWORK NFB NETWORK NFB NETWORK

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1 2 1 22 1 23 1 216 1 215 AAVA-II (Accuphase Analog Vari-gain Amplifi er) type volume control 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. 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 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. 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 n Supplied remote commander RC-200 Allows volume adjust- ment and input source switching. INPUT V- I ConverterVolume Balance AttenuatorI-V Converter OUTPUT Current feedback amplifi er 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 position 16 current switches (65,536 possible combinations) Current values are addedReconversion of current into voltage Volume knob is turned and position is detected CPU AMP FEEDBACK NETWORK AAVA-II operation principle How AAVA-II works AAVA-II operates by feeding the music signal to a V-I (volt- age - current) converting amplifi er 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 combina- tion 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. An essential part of AAVA-II: initial stage current feed- back amplifi er circuitry with high-speed, low-noise operation and excellent high output voltage charac- teristics n Power amplifier assembly featur- ing parallel push-pull output stage directly mounted to large heat sink, instrumentation amplifi er confi gura- tion, and current feedback circuitry n AAVA-II volume control assembly with higher integration density of components and circuitry