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Resumen del manual
For your own benefit, follow alt the instructions in this manual and save it for future reference. The AOCOM GFP-345 is a result ol a thorough examination and réévaluation of all factors affecting the sonic performance of preamplifiers. A great deal of care was taken to insure that the audio performance of the GFP-345 could be maintained for years to come by the selection of top-quality components and circuit topologies. The result is a preamplifier which is as musical-sounding as, and which preserves the dynamic contrasts of, an original performance. The installation and operation of the GFP-345 are described in the following pages. We sincerely hope you will value and enjoy the considerable attention we have given its design and construction. This manual has been written to help you understand the correct operation of the GFP-345. Please read it carefully to fully comprehend all its features and functions and thereby derive the maximum performance from its use in your system. FEATURES GFP-345 The GFP-345 is modeled after the highly innovative internal designs and circuit topologies of both the "Reference Standard” GFP-565 and GFP-555D preamplifiers — accordingly, it is setting new standards for products in its price category. Many of the most significant performance characteristics of the GFP-565 and GFP-555D have been built into the GFP-345. The power supply and low impedance outputs were designed to preserve music dynamics. The amplification stages employ direct-coupled, custom-designed, Hnear-gain amplifiers operating in full Class A to insure the minimum distortion and low-noise required for digital-source material. Buffered tape outputs insure input-signal integrity, and preclude interference with the main-source signal in the preamplifier's circuits when digital or cassette tape recorders are connected (even when these are not operating). The optional phono preamplifier {available as a plug-in board: the PHO-802A) delivers the quietest obtainable performance with unmatched record-squalization accuracy and lowest distortion. Operating in full class A, its unrestricted dynamics and musical accuracy are delivered at surprisingly modest cost. The GFP-345 contains the highest-quality components; never before available in a component of such moderate cost. This should insure stable, dependable operation and long, trouble-free life. • Low-impedance power supply lor best regulation and optimal circuit performance. This type of design insures that music dynamics are delivered through the preamplifier without compression. • Thick power-supply traces on printed circuit board for minimal losses and improved voltage stability. This technique insures constant voltage to all the circuitry, regardless of volume or dynamic demands of the music. • All capacitors are state-of-the-art electrolytics and film capacitors with very low ESR and unsurpassed sonic purity. This design feature provides an audible benefit, the lowest possible distortion of music signals. • Overdesigned mu-metal-shielded power transformer for better regulation. This transformer design eliminates stray hum fields for lowest noise and provides undiminished voltage to circuits for best performance under any demands for level. • Precision, programmable regulators for stabilized, constant DC voltages, regardless of load. This type of regulator insures stable operation ol all circuits regardless of the dynamic demands of the music being played. • Amplifier stages use ADCOM premium-grade ICs selected for their linear operation and sonic quality. These linear amplifiers insure extremely low noise, low distortion and low DC offset for best performance with either set of preamp outputs. • Amplifiers are operated in pure Class-A mode to insure lowest distortion regardless of the signal level or setting of the level control. • Entire signal path is direct-coupled from input to output. Direct coupling minimizes the number of components signal must go through, preventing degradation of the music. • Two sets of outputs: OUTPUTS LAB are direct-coupled. They provide a signal in the most straightforward, simplest path. OUTPUTS NORM are capacitor-coupled using precision, high-grade film capacitors for power amps which can not accept ultra-wide bandwidth inputs. 1 • Low-output-impedance {100 ohms) from both sets of outputs to reduce interaction of connecting cables and other equipment and preserve music dynamic contrasts. • Five sets of inputs, front panel controlled, including TAPE IN; six sets if the EXTERNAL PROCESSOR IN jacks are used also as an auxiliary input. • Low-impedance tape outputs {100 ohms) to perfectly interface with any type of tape recorder. This technique allows the preamp to mate with any type recorder, including DAT and DCC, and insures the best recording characteristics independently of the cable used and the load impedance of the tape recorder inputs. • Buffered tape outputs to preserve input-source-signal integrity and pr...