Whirlwind manual MD-1 MIC TO LINE DRIVER / HEADPHONE MONITOR

www.whirlwindusa.com

MD-1MIC TO LINE DRIVER / HEADPHONE MONITOR

The Whirlwind MD-1 is the culmination of many years of joint product development between our engineers and suggestions from professionals such as you. This compact portable unit combines a high quality microphone preamp- line driver with a headphone amplifier designed to monitor the mic preamp or be used independently. The MD-1 employs two 9-Volt batteries and provides enough gain to drive both headphones and long signal lines and allow for maximum headroom in the mic preamp.

FEATURES

•Up to 66 dBm of gain adjustable with analog style potentiometer.

•Finest quality mu metal shielded input transformer.

•Wide range frequency response.

•Low input noise and harmonic distortion.

•Low susceptibility to radio frequency interference.

•Balanced, transformer isolated input and output connections.

•Headphone section monitors main input, separate balanced headphone line input or mix of both.

•Rugged construction.

•9 Volt battery power with reasonable battery life.

CIRCUIT DESCRIPTION

The input is a via a female XLR connector with a switch for mic or line level mode. In MIC mode, a mu metal shielded input transformer provides 20dBm of impedance gain with low THD. The MD-1 provides 18VDC phantom power when the MIC/LINE switch is in the MIC mode and the phantom power switch is on. In LINE mode, the audio signal bypasses the transformer and is presented to a standard active balanced input configuration. After the input section, the signal is routed to the active gain circuit.

The active gain section uses a low noise IC to produce up to 26dBm of forward gain. The GAIN control provides both attenuation and gain to the user. With the gain control fully CCW, the circuit provides 50dBm of attenuation (line input mode). With the gain control fully CW (mic mode) the unit will provide 66dB of forward gain from input to output (18dB from the input section, 28dB from the active section and 20dB from the output transformer). After the active gain section, the signal is sent to both the output driver and the headphone amplifier. In the output driver circuit, the signal passes through an IC that buffers the signal, drives the output transformer (which adds 20dBm of impedance gain), provides isolation and helps to maintain maximum common mode rejection. The transformer output is connected to the DRIVER side of the output selector switch. In the