EC21

About the EC21

The Audio Research EC-21 is a vintage active two-way electronic tube crossover introduced around 1980. It allows biamplification of quality loudspeaker systems by splitting the audio signal into two frequency bands with adjustable crossover points and slopes. The unit uses three 12AX7 vacuum tubes (McIntosh branded JJ tubes in serviced units) to provide a warm, tube-driven sound characteristic. It features an infinitely variable, fixed frequency and slope design, with a crossover frequency typically set around 125 Hz but adjustable via capacitor kits. The bass output gain is adjustable from 0 dB to +9 dB, with an 18 dB per octave slope. The EC-21 improves dynamic range and reduces distortion by biamplification, enhancing system performance and efficiency. It includes a power-on delay for tube stabilization (approximately 105 seconds). Dimensions are approximately 19" W x 5 ¼" H x 10 ¼" D. The unit is highly regarded for its sonic quality and vintage tube warmth, making it a sought-after piece for audiophiles seeking classic tube crossover performance.