207d
instruction Manual
Aphex Systems Ltd. Model 207D
Page 20
207d
2-ch tube mic preamp with adc
Page 21
Aphex Systems Ltd. Model 207D
Specifications
6.2 ARCHITECTURAL SPECIFICATIONS
Basic Description
A two-channel electronic preamplifier for microphones and instruments comprising a transformerless balanced
microphone input and a high impedance unbalanced Instrument input for each of the two channels. The pre-
amplifier shall comprise a Reflected Plate Amplifier tube-type transformerless output stage. The preamplifier
shall further comprise an operating level switch to select between nominal output levels of +4dBu and -10dBV.
The two preamplifier channels shall be operable independently. There shall be two industry standard analog
output jacks per channel, an XLR 3-pin male, and a 1/4” TRS phone jack. In addition to the analog outputs,
a 24-Bit digital audio S/PDIF output from an internal analog-to-digital converter shall be provided. Additional
specifications are stated below.
Microphone Input
The input jack shall be a standard XLR-type 3-pin female. The input impedance shall be nominally 2000 ohms.
All normally operated controls for the mic input shall be placed on the front panel. The mic preamp shall com-
prise the following features: 1.) Sele48VDC Phantom Power; 2.) Selectable Polarity; 3.) Selectable 20dB
Pad; 4.) Selectable 70Hz 12dB/Octave Low Cut Filter; 5.) Selectable Peak Limiter; 6.) Continuous Gain Control.
The selectable peak limiter shall be a type that limits the mic signal before any amplification to prevent input
overload. The input stage shall be transformerless and actively balanced. The preamplified microphone signal
shall be sent through an INSERT jack to the output stage to facilitate the use of outboard signal processing.
Instrument Input
The input jack shall comprise a 1/4” phone jack. The input impedance shall be 1 megohms. The input stage
shall comprise a low noise JFET integrated circuit amplifier.
Insert Jack
A 1/4” TRS phone jack shall be provided at the rear panel for inserting outboard signal processing for the micro-
phone input only. The insert jack shall comprise an unbalanced send and an unbalanced return that operate
at nominal -10dBV levels. The point of insertion shall be between the microphone preamplifier and the tube
output stage.
Digital Outputs and Sample Rates
The digital sample rate shall be selected from internal frequencies of 441., 88.2, 48, and 96kHz. Additionally,
an external word clock input shall be provided to receive clock frequencied from 32 to 96kHz. The outputs shall
be both AES3 on XLR and S/PDIF on RCA.
Physical Properties
The device shall be packaged in an all metal chassis measuring 19” (482.23mm) wide, 1.75” (44.42mm) high,
with an overall depth of 8.25” (210mm). Depth behind the front panel shall be approximately 8” (203mm).
The device shall have a net weight of approximately 6lbs. (2.73kg) and is capable of mounting in a standard
electronic equipment rack.
Power
The unit shall have a self contained power supply operating from the ac line. Primary voltage, connectorization
and agency listings shall be appropriate to meet local requirements.