Audio Research EC-4A // Vintage / 3-way Electronic Tube Crossover (475060-1)

The Audio Research EC‑4A is a rare breed: a fully analog, tube-powered, three-way crossover that does its heavy lifting behind the scenes with grace and precision. Sporting six 12AX7 tubes and fixed crossover points—switchable via capacitor banks—it offers surgical clean division of your signal path without ever leaning on op‑amps or digital tricks. It sounds smooth and musically coherent, with that unmistakable warm vibe ARC is known for—though some users note the power supply could use an upgrade for extra finesse. In short, the EC‑4A isn’t just a component—it’s an audiophile’s secret weapon for building active, tube‑rich speaker systems that breathe just like live music.

S/N: 475060-1

• All tubes test good
• All are 1st order filters
• Bass is -6dB at 150Hz, -20dB at 600Hz
• Midrange is -6dB at 50Hz and 1kHz, -20dB at 10Hz and 6kHz
• Treble is -6dB at 250Hz, -20dB at 50Hz
• Midrange and especially treble would need to be changed if used with "normal" 3-way speaker or many a tweeter might meet a sad end