Features ALL-TUBE audio path 12AU7WA + 6414 per ch. Unbalanced 1/4" Inputs And Outputs and... Balanced Transformer Coupled XLR Inputs And Outputs Hi-current drive <50 Ohm 1/4" & XLR outputs Silent conductive plastic INPUT attenuators Description Product Description Set it and forget it! Our ELOP® Limiters make your job easy. The principle of operation is based around using a rectified sample of the audio to shine an LED (Light Emitting Diode) onto an LDR (Light Dependent Resistor). The photo-resistor in combination with a fixed resistor simply act as a changing voltage divider to attenuate the signal-- like a smart volume control. A similar principle was found in the older **Teletronix & Urei **LA-2A, LA-3, and LA-4 units which used a slower electro-luminescent panel-light on a conventional LDR encased in a light-tight enclosure. Ours uses modern VACTROL technology (but with a trick!) for exact sample-to-sample tracking and no high frequency loss while digging deep into limiting-- problems commonly associated with older LA-series limiters and other opto-based units.