Accuphase C 2400 Brochure

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Accuphase C 2400 Brochure

Extracted text from Accuphase C 2400 Brochure (Ocr-read)

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Innovative AAVA type volume control guarantees great sound and top performance Experience volume adjustment without deterioration in S/N ratio or distortion. AAVA and other circuit modules are arranged on motherboard separately for left and right channels. Fully dual monaural construction features two separate power transformers. Dedicated phono equalizer unit allows analog record reproduction with superb fidelity. BUFFER BUFFER V- I Converter CPU OUTPUT INPUT I -V Converter Volume Balance Attenuator GAIN VOLUME5 46 37 28 19 MIN MAX The C-2400 inherits the design technology of the outstanding Accuphase C-2800, featuring the same AAVA type volume control. One of the most important aspects of a preamplifier is how it handles volume adjustment. AAVA (Accuphase Analog Vari-gain Amplifier) is an innovative concept that differs radically from conventional variable-resistor type volume controls. 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 the amplifiera 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 monaural 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-2400, 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 phono equalizer unit (AD-2800) for faithful playback of analog records is also available. AAVA (Accuphase Analog Vari-gain Amplifier) volume control 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 resolutionAAVA adjusts the listening volume by means of 16 current switches which are operated by 16 weighted V-I converter amplifiers. The number of possible volume steps set by the combination of these conver ter amplifiers is 2 to the power of 16 = 65,536. AAVA maintains high S/N ratioWith 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 conver ter amplifiers (changing the actual gain), there is no change in impedance and thus no deterioration of S/N ratio. Changing the volume with AAVA does not mean introducing noise or detracting from the high performance of the amplifier. 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. Simple circuit configurationAAVA 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 processingThe 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. 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. 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 signal16 current switches (65,536 possible combinations) AAVA operation principle 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 positionCurrent values are addedReconversion of current into voltage Volume knob is turned and position is detected AAVA operation principle 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 volume. Finally, the combined current is converted back into a voltage by an I-V (current - voltage) conver ter. Input buffer, 16 V-I converter amps and current switches, current adder, I-V converter amp, and other circuitry on modular AAVA unit, installed separately for left/right channel on motherboard

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Selectable preamplifier gain The overall gain of the preamplifier can be set to 12, 18, or 24 dB with a rear-panel switch. This allows the C-2400 to operate at optimum gain in any kind of system. Logic-controlled relays assure high sound quality and long-term reliability The C-2400 offers a host of input and output connectors and functions. Strategically placed relays prevent any signal degradation that could occur if the signal has to travel through long paths for connection and function switching. Fully dual monaural 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 dual monaural approach assures total freedom from unwanted mutual interaction. Tone controls use summing active filters for highest sound quality The tone control circuitry in the C-2400 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 design provides efficient control without degrading signal purity. F1 VR1 F2 VR2 Supplied remote commander RC-32 Allows volume control and input source selection. Factory default: 18 dB Flexible input/output configuration Dedicated headphone amplifier optimized for sound quality EXT PRE function allows use of external preamplifier Optional phono equalizer allows playback of analog records Supplied remote commander with volume control function Versatile features: Recording/playback/monitoring facilities for 2 recorders Copy function Loudness compensator for fuller bass at low levels Subsonic filter removes ultra low frequency noise Phase selector Attenuator Principle of tone control circuitry (summing active filter) Input Output