The Warm Audio WA-2A is a transformer-balanced, high-voltage, opto (light-controlled) all-tube compressor with a completely discrete signal path and through-hole component topology. It features custom, large-core Cinemag USA input and output transformers, four premium vacuum tubes, and Kenetek opto-cells.FeaturesUSA-made CineMag input and output transformersUSA-made Kenetek T4B opto attenuator. Socketed to allow for retro-fitting with vintage (or other) opto-cellsPremium Tung-Sol and Electro-Harmonix tubes. 2 x 12AX7, 1 x 12BH7, 1 x 6AQ5 (or 6P1 - interchangeable)Variable Pre-emphasis knob (via the back-panel) allows for compression hi-pass filteringStereo-link capability via TRS connector and knob on back panelSpecificationsXLR and TRS balanced line level inputs - 600 Ω impedanceXLR and TRS balanced line level outputs - 600 Ω impedanceFrequency Response +/- 1 dB, 15 Hz to 20 kHzGain 40 dB +/- 1 dBInput Level + 16 dB maximumOutput Level +10 dB nominal, + 16 dB maximumDistortion Less than 0.5 % THD at +/- 10 dBmNoise = - 74 dBAttack Time: 10 millisecondsRelease Time: 0.06 seconds for 50% release; 0.5 to 5 seconds for complete releaseMeter: shows both dB gain reduction and dB outputPower: 115/230 volts (switchable), 50/60 HzDimensions:19" rack-mount chassis, 2U19" x 7" x 3.5"Weight: 12 lbs.Note: further information can be found within the "WA-2A User Manual" under the "Documentation" tab above. Warm Audio WA-2A Vintage Style Optical Compressor.