Black Lion Audio T4BLA Opto ElementThe ultimate opto upgrade. At the heart of almost every optical compressor lies a T4b style Optocell. When designing the B172a compressor, Black Lion Audio tested every single readily available and boutique T4b one could get their hands on and found the options to be sorely lacking. Black Lion found that no available optocells were holding up to their rigorous testing nor did they deliver the feel and quality that one should expect from a Black Lion