Solid-state preamplifier with passive/active modes
All pre-owned product is tested in our service department and have been passed for sale... and comes with a 90 day warranty!
In nice condition Some smudges and small scratches on one side and top. Manual is included, but Remote control is NOT included. Circa 1999
Original box and backing are NOT included, but we will pack carefully. Specs are last image.
Stereophile LOVED this piece - see the review HERE. "Adcom's GFP-750 is a remarkable preamplifier. It's well-built and elegantly designed—on the inside, where it counts. I've gone just gaga over it, not simply because it performs well for the money, but because it begs comparison with the best preamplifiers I've ever heard. Period. No matter how much you've budgeted for a stereo preamplifier, listen to the GFP-750 first."
Famous Nelson Pass design.
The GFP-750 can be operated either as a completely "passive" (no gain) unit, with absolutely minimal sonic impact, or as a sophisticated active (utilizing active components and providing gain) preamplifier. In passive mode the GFP-750 is strictly a "line level input switcher", with its high quality four gang volume attenuator that lets you adjust the volume. While its active circuitry is both unique and superb (details later), you always have the option of using the GFP-750 in this ultimate passive mode, for control with maximum fidelity.
Any "line level" source that you have (CD player, tuner, DVD player {audio output}, tape deck, etc.) can be directed through the GFP-750 in the passive mode. The only effect the GFP-750 will have on the sound is volume adjustment, using the built-in precision four gang volume attenuator. In this mode the GFP-750 adds no noise, no distortion, in fact, it changes nothing. So, as far as your ears are concerned, it's sonically invisible. And that's our goal, isn't it?
Adcom's active approach- The engineering design specifications for the GFP-750 were simple:
Minimize circuitry (the fewer parts and gain stages, the less chance there is for sonic degradation). Reduce or eliminate negative feedback. Incorporate true differential balanced audio signal paths for the best sound quality. Use high quality MosFet transistors throughout. Power the internal circuits of the GFP-750 with a power supply that can keep up with any conceivable signal demand. Incorporate an easy way to add home theater processing while maintaining the best performance.
Adcom's creative engineering solutions: The GFP-750 has only one active gain stage. It's a pure Class A design, long regarded as the best sounding type of amplifier circuit. The active devices in this gain stage are exclusively reference grade HexFet transistors (an advanced hybrid MosFet device) that offer superb, dynamic sound with a smoothness and openness heretofore considered unobtainable in solid state devices. Countless hours of intense listening have proven to us that well designed amplifier stages using MosFet devices are the smoothest and most natural sounding. So you'll find these more expensive MosFets and HexFets throughout Adcom's line, because we won't compromise performance to save money on parts.
The GFP-750's active circuits have extremely wide frequency bandwidth for uncolored sound, yet they've been designed to be impervious to RF (Radio Frequency) interference, as an added assurance that noise won't be an issue. The GFP-750 features both balanced XLR (for the CD) and unbalanced gold plated RCA input circuits. Using the balanced XLRs assures the quietest signal transfer between components. Balanced XLR circuits are also included for output connection to an appropriately equipped power amplifier, like the GFA-5802.
The GFP-750's output stage acts as pure current source (as opposed to a voltage source). That means it's effectively isolated from the power amplifiers input impedance and the impedance of the cables used between them. (High quality cables are important, but should have less of a sonic impact on the GFP-750 than some other preamp designs.) The GFP-750 incorporates a power supply that would more typically suit a receiver or integrated amplifier! It includes a large toroidal (donut shaped) transformer which offers less internal resistance to current flow and lower induced hum than traditional transformer designs. This transformer has multiple output taps, one for each channel. Individual voltage regulators are mounted to special aluminum heat sinks for maximum stability and to allow high current draw during dynamic passages. Selected high capacity storage capacitors are mounted close to the individual circuit they service to supply clean, filtered power to the active components.
The GFP-750's component parts are carefully selected reference grade devices, for maximum sound quality and minimum noise. The GFP-750 is direct coupled, eliminating capacitors entirely, where possible, to reduce their sonic impact.
Input switching is accomplished with hermetically sealed high quality relays. This eliminates the noise and other problems associated with alternate switching methods.
