Pearl Black Pearl coolers have been in continuous production for 20 years, during which time Black Pearl has produced over 300,000 coolers for audio systems worldwide. They are undoubtedly the longest-running and most successful vacuum tube components. Black Pearl research began in the early 1950s by the US military and aerospace industry. Pearl coolers effectively reduce glass temperature, significantly extending the lifespan of soft glass-enclosed vacuum tubes used 50 years ago. Through extensive research and robust mechanisms, Black Pearl developed coolers that extend the life of lamps.