Introduction, Features gfp-345 – Adcom GFP-345 User Manual
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INTRODUCTION
Piease read thoroughly these operating instructions forthe G FP-345 before connecting or attempting to operate this unit.
For your own benefit, foHow alt the instructions in this manual and save it tor future reference.
The ADCOM GFP-345 is a result of 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-346 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, linear-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-equalization 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 for 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 tenefit, the lowest possible distortion of music signals.
• Overdesigned mu-metal-$hielded 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 of 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.