⭕ ONE OWNER THRESHOLD SA/1 CLASS A MONOBLOCK AMPLIFIERS WITH CONSECUTIVE SERIAL NUMBERS 2517 AND 2518. THESE AMPS CAN DRIVE A 1 OHM LOAD WITH EASE ACCORDING TO NELSON AND WORK QUITE WELL WITH MY 1 OHM VERSION OF THE APOGEE SCINTILLAS DESIGNED BY NELSON PASS FOR THRESHOLD AND COMPARABLE TO SIMILAR COMPONENTS FROM KRELL, LEVINSON, BOULDER, AND OTHER. UPGRADED BY THRESHOLD TO OPTICAL BIAS E SERIES WITH BALANCED INPUTS WHICH ARE RARE AND PRICEY UPGRADE ON THIS MODEL AS WELL AS THE STANDARD RCA INPUTS, A REAR TOGGLE SWITCH SELECTS BETWEEN THEM GOLD OVER NICKEL OVER COPPER CIRCUIT BOARDS THROUGHOUT THE ENTIRE SIGNAL PATH INCLUDES OEM POWER CORDS, BOXES AND PACKING, OWNERS MANUAL AND BROCHURES ON SA SERIES AMPS! DELIVERY CAN BE ARRANGED OR COLLECTION LOCALLY. IN EXCELLENT CONDITION, BOTH FUNCTIONALLY AND COSMETICALLY. SEEN VERY LIGHTLY USE.