Architecture & Engineering Specifications
The microphone preamplifier shall perform the function of amplifying each of 8 discrete microphone channels and converting into digital audio formats. Each channel shall have a microphone preamplifier input, an analogue line output, and digital outputs in both copper and optical formats. The copper output shall be compliant with the Audio Engineering Society AES3-2009 standard and the optical output shall be in the proprietary Alesis ADAT format.
The microphone preamplifier shall provide variable gain from +10 dB to +60 dB, and selection switches for phase invert, -20 dB pad and +48 V phantom power for each channel. Swept second-order (12 dB/octave) high and low pass filters shall also be provided for each channel, with frequency ranges 10 Hz to 400 Hz and 1 kHz to 40 kHz respectively.
The microphone preamplifier shall have a precision clock reference provided by a temperature-controlled crystal oscillator (TCXO) with 1 part-per-million (1 ppm) stability.
The microphone preamplifier shall provide analogue to digital conversion with 24 bit resolution at 44.1 kHz, 48 kHz, 88.2 kHz and 96 kHz sampling rates with the option of synchronising to either the internal 1 ppm precision clock reference oscillator or the external word clock input.
The microphone preamplifier shall have each analogue input paralleled on both individually on industry standard XLR connectors and combined on a 25 way D-type connector.
The microphone preamplifier shall have a 25 way D-type connector with connections for the electronically balanced analogue output for each channel.
The microphone preamplifier shall have two 25 way D-type connectors for the AES3 digital outputs, to support operation at both standard 44.1/48 kHz and high 88.2/96 kHz sample rates.
The microphone preamplifier shall have two TOSLINK optical connectors for the ADAT outputs, to support operation at both standard 44.1/48 kHz and high 88.2/96 kHz sample rates. The microphone preamplifier shall have word clock input and output connections on 75 Ω BNC connectors.
The microphone preamplifier shall include an auto-ranging universal switch-mode power supply for use on a worldwide basis.
The microphone preamplifier shall be housed in a standard 1U 19" rackmount chassis, and shall be 483 mm wide x 301 mm deep x 44 mm high (19.0" x 11.8" x 1.7"), with nominal weight 4.3 kg (9.5 lbs). The microphone preamplifier shall be installed in a rack frame or road case capable of safely supporting its weight. Input, output, and power connections shall be made at the rear panel of the microphone preamplifier. Installers shall allow adequate space at the rear for connection and disconnection of input, output, and power connections. The power requirements shall be 100 to 240 VAC, 50 to 60 Hz.
The microphone preamplifier shall be the Midas model XL48 and no other alternative shall be acceptable.