Accuphase C 2000 Brochure
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Innovative AAVA type volume control Adjusts listening level without deterioration in S/N ratio or distortion. Dual mono construction with two power transformers and separate modular AAVA amplifiers for left and right channels mounted on motherboard. Option board slots provide support for digital input signals and high-grade analog record playback. The C-2000 inherits the design technology of the Accuphase C-2800 and C-2400, featuring the same AAVA type volume control. AAVA (Accuphase Analog Vari-gain Amplifier) is an innovative concept that differs radically from conventional variable-resistor type volume controls. It tackles one of the most important aspects of a preamplifier, namely how it handles listening level adjustment. In AAVA, amplification and volume control are fully unified, eliminating all mechanical contact points. Pure analog processing ensures optimum performance and superb sound. Doing away with the variable resistor in the signal path has numerous advantages and brings theamplifier a significant step closer to absolute purity in signal transmission. Another benefit of AAVA is that it is configured only with highly reliable semiconductor components. This assures that performance and sound quality will remain undiminished for many years to come. The large volume knob on the front panel employs a position detection method that combines superb precision with a smooth conventional feel. The power transformer, filtering capacitors and all other parts of the power supply are duplicated for the left and right channel. What's more, all unit amplifiers such as for line input, balanced output, and AAVA are also entirely separate forthe two channels, arranged on a high-quality motherboard. This fully monophonic construction prevents unwanted interaction both on the electrical and the physical plane. The line amplifier with integrated volume control is a major aspect of the C-2000, but there are also a host of other attractive features in this superb analog preamplifier. Tone controls and loudness compensator allow fine tuning of the sound. Tape recorder and copying facilities as well as an EXT PRE function provide connection flexibility. A range of option boards allows the amplifier to handle digital input signals and to realize high-grade playback of analog records. BUFFER BUFFER V- I Converter CPU OUTPUT INPUT I -V Converter Volume Balance Attenuator VOLUME5 46 37 28 19 MIN MAX 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. The volume can be adjusted without any deterioration in sound quality. 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. Modular AAVA unit contains input buffer, 16 V-I converter amps and current switches, current adder, I-V converter amp, and other circuitry on three boards, plus a CPU for AAVA control. Modules are installed separately for left/ right channel on a mother- board. n nn n nVolume 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. n nn n nAAVA maintains high S/N ratio and unchanged frequency response With conventional volume controls, the impedance increases significantly at settings that correspond to normal listening levels, thereby leading to increased noise. Because there is no change in impedance with AAVA, there is no deterioration of S/N ratio, and frequency response also is not affected. Adjusting the volume with AAVA does not mean introducing noise. High S/N ratio is maintained, and there is no alteration of sound quality. n nn n nNo more left/right tracking differences or crosstalk Because AAVA is an electronic circuit employing fixed- value resistors, there is vir tually no left/right tracking error also at low volume levels. Since channels can be kept separate, crosstalk also does not present a problem. n nn n nSimple 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. n nn n nAAVA 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 reconver ts the current into a voltage. The entire process is carried out in the analog domain. n nn n nSame 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. n nn n nAttenuator 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. AAVA (Accuphase Analog Vari-gain Amplifier) volume control AAVA principle 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 position Reconversion of current into voltage Current values are added Volume knob is turned and position is detected AAVA operation
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Output Input F1 –A1 – A2 VR1 F2 VR2 Response in dB Frequency in Hz 10 100 1k 10k 100k 16 12 8 4 0 –4 –8 –12 –16 100Hz BASS TREBLE 40Hz 20kHz 8kHz Logic-controlled relays assure high sound quality and long-term reliability The C-2000 offers a host of input and output connectors and functions. Strategically placed relays allow straight and short signal paths, to prevent degradation that could occur if the signal had to travel long distances for connection and function switching. Dual mono construction with separate power transformers and separate board-mounted unit amplifiers for left/right The input buffer, AAVA circuit, balanced output and other amplifier circuitry are configured as five separate units for each channel, arranged neatly on a motherboard. Power transformers and smoothing capacitors are also separate for the two stereo channels. This thorough dual monophonic approach assures total freedom from unwanted mutual interaction. Tone control circuit principle (using summing active filters)Tone control characteristics Tone controls use summing active filters for highest sound quality The tone control circuitry in the C-2000 uses summing active filters. The illustration below shows the operation principle of this circuit. The flat signal is passed straight through, and only when an adjustment is required, the characteristics are created at F 1 and F 2 and added to the signal, thereby producing the desired change. This designprovides efficient control without degrading signal purity. The turnover frequency for the bass control (max. ±8 dB) can be switched between 40 and 100 Hz, and that for the treble control (max. ±8 dB) between 8 kHz and 20 kHz. nSupplied remote commander RC-20 Allows volume control and input source selection.