Accuphase C 275 V Brochure

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Accuphase C 275 V Brochure

Extracted text from Accuphase C 275 V Brochure (Ocr-read)

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The new joy of analog -“ realized in a superb high-end preamplifier. Current feedback technology, Teflon-based printed circuit boards, four separate unit amplifiers, fully dual-mono construction with separate power supplies. Optional phono equalizer unit allows top-quality analog disc reproduction. All preamplifiers from Accuphase are based on balanced signal transmission, taking a no- compromise approach to quality. Furthermore, they reflect the rich experience accumulated by Accuphase during many years of building state-of- the-art components. The C-275V is a fully redesigned successor to the C-275, making extensive use of sophisticated technology first introduced in the highly renowned C-290V. As an analog preamplifier, it has been honed to an even higher degree of perfection. Every single part was carefully selected through intensive listening tests. It offers a full complement of sound tailoring features such as tone controls and a loudness compensator. The basic circuit design employs current feedback topology developed by Accuphase, assuring outstanding performance combined with excellent sound quality. As shown in Figure 1, in its standard configuration the C-275V is a dedicated line amplifier, but by installing an optional phono equalizer unit in a special slot on the rear panel, it allows high-grade analog disc reproduction as well. In keeping with the aim of creating the ideal line amplifier, the balanced output stage of the C-275V employs symmetrically bridged feedback, resulting in a floating design where the signal is kept entirely separate from the ground line. This lavish approach is highly desirable in a line amplifier and assures the best possible performance. The printed circuit boards are an important element of a preamplifier in regards to electrical performance as well as sound quality. In the C-275V, these are made from a Teflon material (glass fluorocarbon resin) with low dielectric constant and low loss, for optimum sound. Less frequently used controls are located behind a sub panel, and the elegant gold-colored panel face has a stylish appeal. Even in the smallest detail, the C-275V exudes an atmosphere of sheer class which makes this analog preamplifier a joy to own and rapture to listen to. Current feedback topology prevents phase shifts The amplifying circuits in the C-275V use the current feedback principle for negative feedback. Figure 2 shows the operating principle of this design. At the input point of the feedback loop, the impedance is Fig. 1 Block diagram of C-275V (one channel)(Option) kept low for current detection. A trans-impedance amplifier conver ts the current into a voltage to be used as the feedback signal. Since the impedance at the current feedback point (current adder in Figure 2) is very low, there is almost no phase shift. Phase compensation therefore can be kept at a minimum. A minimal amount of NFB results in maximum improvement of circuit parameters. The result is excellent transient response and superb sonic transparency, coupled with utterly natural energy balance. Figure 3 shows frequency response for different gain settings of the current feedback amplifier. The graphs demon- strate that re- sponse remains uniform over a wide range. Balanced output stage with bridged feedback In balanced signal transmission, two identical signals are transmitted simultaneously with inverted phase and combined at the receiving end, thereby canceling out common-mode noise and interference. This principle is one of the requirements for truly high-quality sound. The principle of balanced sound transmission is shown in Figure 4. The outputs of the two amplifiers are connected to form a cross-feedback loop, which sends the symmetrical (+) and (-“) signals with low impedance to the next stage. The signals are isolated from the ground line, resulting in an ideal balanced circuit. Even if one side of the output is grounded, both amplifiers continue to operate, and the output voltage does not change.Discrete line amplifier for optimum sound The line amplifier is a pure complementary push- pull circuit. It is built from discrete components and employs the superior current feedback principle. Phase compensation can be kept to a minimum, resulting in realistic ambience. Printed circuit boards made from Teflon with low dielectric constant and low loss The printed circuit boards for the signal-carrying circuits are made of Teflon, a glass fluorocarbon resin material. Teflon has a stable, low dielectric constant as well as superior heat resistance, excellent high-frequency characteristics, and many other desirable proper ties. As a result, signal purity is enhanced and there is a drastic improvement in perceived S/N ratio. * Teflon is a registered trademark of DuPont USA. Complete mono construction with separate transformers for left and right channels The power supply of the C-275V employs a dual- mono approach with separate power transfor mers and filtering capacitors for the two stereo channels. Each unit amplifier is equipped with a wide-range low-impedance voltage regulator to eliminate possible interference between stages. Tone controls use summing active filters for highest sound quality The tone control circuitry in the C-275V was specially designed with summing active filters such as found in high-quality graphic equalizers. Figure 5 illustrates the operation principle of (High) (High) Gain Frequency Input Output

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* Photo shows the amplifier with optional phono equalizer unit AD-275V installednRemote commander RC-26 allows volume control and input source selectionnMother PCB with gold-plated copper paths supports the four unit amplifiers (line and balanced amplifiers), as well as filtering capacitors and peripheral circuitry. Unit amplifier in thick aluminum housing this circuit. The flat signal is passed straight through, and only when an adjustment is required, the characteristics are created at F1 and F2 and added to the signal, thereby producing the desired change. This design provides efficient control without degrading signal purity. Vibration-free design with unit amplifiers in aluminum enclosures fastened to 8-mm hardened aluminum chassis The C-275V has four unit amplifiers, two each for the line input and line output in each channel. Each unit is powered by its own local voltage regulator circuitry, and is housed in a strong aluminum enclosure, to prevent interference between units. Hermetically sealed relays connected directly to gold-plated input/output jacks Logic-controlled relays for signal switching assure high sound quality and long-term reliability The use of logic-controlled relays at strategic locations makes it possible to keep signal paths extremely short. The relays used in the C-275V are high-performance hermetically sealed types as used in professional communication applications. The contacts are twin crossbar types plated with gold and silver palladium alloy, for minimum contactresistance and outstanding long-term reliability. Other features nVolume control designed for sonic purity nSupplied remote commander for volume adjustment and program source switching nDedicated headphone amplifier for superior sound nVersatile array of functions mTape recorder facilities with monitor switch and copy switch mOutput phase selector button mLoudness compensator with three selectable characteristics mSubsonic filter removes ultra low frequency noise