The MP73a is a 500 Series microphone preamp it is a one-channel vintage style microphone, line and instrument preamplifier. The signal path uses only discrete components like resistors, capacitors and transistors. The microphone and line input and the line output are transformer balanced, using two different transformers, each one optimized for its purpose. Great use for guitars, bass, keyboards and other instruments.The circuit used in the MP73a is similar to the preamp section in the classical 1073 module with a cor- responding sound character that is warm, punchy, sweet and musical. These classiccharacteristics have been heard on countless recordings through the years and it is a versatile sound that works very well on most sound sources and in most genres. The essence of this sound is now available at a surprisingly low cost, making it available to nearly everyone.