503 Mic Pre with Limiter is a single-channel microphone preamplifier with switchable mic/line input, four low-noise amplification stages and a warm, clear tone across 20 Hz to 20 kHz. It delivers up to 77 dB of gain, a maximum input around −10 dBu and a +22 dBu output, with a noise floor of −128.6 dB. The soft-knee limiter (≈12:1) keeps peaks under control, and the unit provides phantom power, a 75 Hz high-pass filter and polarity reverse.