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GRANITE AUDIO 770fp - The high B+ voltages and high-current filament voltages are on separate layers from the signal path and trace circuits, and isolated from them by a layer of pure copper.  This gives excellent ratings for low noise, extra shielding, and low cross talk between channels and inputs.  All traces are set at maximum distances apart and only cross at perpendicular orientation, as opposed to parallel which would generate noise and crosstalk.  This differs from most PC boards which are single layer with no shielding.  The traces in a single layer board must run parallel and unshielded , which causes all sorts of interference.  The 4-layer board is cleaner and quieter sounding, as well as fully shielded.

Why tubes?  A tube is a true valve.  A transistor is a switch.  Tubes let the music flow, while transistors are incessantly turning your music on and off by their very nature.  Ever notice how the water flows smooth from conventional shower heads while it pulsates from massage heads?  The on-off pulses feel good on your back, but they're harsh on your music and add to listening fatigue the same way your back gets numb to the water pulses after a while.

All the quality parts from Vishay, Alps, Sprague, Alcoswitch, Electroswitch, and Holco are mounted directly to the PC board.  There is only a few inches of wire to connect the power supply board to the main amp board.  Essentially the main board is one piece with all the parts attached. 

The power supply is on a separate board to eliminate potential ground loop problems which cause low frequency hum.  The filaments are filtered and rectified with low-noise  ultra-fast recovery Schottkey rectifiers which produce a smoother voltage rail than conventional silicone rectifiers.  Switches and contacts are either gold or silver.  The RCA inputs are hard gold plate over silver over copper for the best in long-life wear and maximum transfer of a clean unaltered signal.  The Model 770 uses tube rectification because we believe it sounds better and gives a fuller richer bass sound.