In the 1980s, before Audio Research had completely committed to vacuum tubes, they did make a couple of pieces of solid state gear. Not surprisingly, those pieces were very well built and their sound, like most Audio Research gear, is jaw-dropping. The SP7 is a solid state stereo preamplifier that features 4 line level inputs and a moving magnet phono input.
At the heart of the SP7 are (4) AM8 modules. These Analog Modules were rumored to be high performance op amps but their true nature was never fully disclosed by ARC - they're certainly cool looking. Two of them are used for the line stage of the preamp and two of them are used for the moving magnet phono section.
These preamps are renowned for their surprising clarity and reliability. The surprising realism of this one nearly knocked me out of my chair when I fired it up after service. Huge soundstage and remarkable, non-fatiguing detail are the characteristics of this preamp. It also has an airy quality that I'm only used to hearing in modern audio equipment.
This one had its power supply capacitors replaced as well as the associated diodes. It uses a very thick double-sided PCB and the caps are soldered directly to the surface of PCB in some places. All voltages were confirmed and the unit is working just as it should. Cosmetically, it is in good condition for its age. Somewhere along the way, the screws holding the top and bottom cover were replaced - please see photo.