Warm Audio WA-2A optical compressor 2A-style, transformer weight, high voltage, opto (light-controlled) tube compressorfully discrete signal path USA-made CineMag in and output transformersUSA-made Kenetek opto-damper custom-made for retro-fitting opto cells first-class Tung-Sol and Electro Harmonix tubes: 2 x 12ax7, 1 x 12bh7, 1 x 6aq5 (can be replaced by a 6p1)adjustable pre-emphasis for high-pass filtering stereo link capablebalanced XLR and TRS line inputs: 600 Ohms