BUGERA Amplifier Tube (5AR4) The 5AR4 is a classic, more powerful version of the 5V4 rectifier tube  a component used to convert AC to DC The BUGERA 5AR4 is built to exacting specifications and This rectifier tube provides a tighter sound than the 5V4 due to its shorter rise time and yet produces the famous sag with the compressed feel that makes your guitar sing Premier engineering provides superior reliability and consistency that makes the BUGERA 5AR4 one of the best you can buy