Biamp Rauland AP4601 and AP4603 are professional audio mixers designed for a wide range of applications, including sound reinforcement, broadcast, and recording. The AP4601 is an eight-input mixer with two independent notch filters, a high-pass filter, and a limiter. The AP4603 is an expander unit that adds eight inputs to the AP4601, for a total of 16 inputs. Both units feature XLR and TRS connectors, phantom power for condenser microphones, and a variety of controls for adjusting the sound.