3400-daa.ib.doc
Page 3 of 8
25-07-2002
Description.
The IRT DAA-3400 is an eight output non-reclocking distribution amplifier for AES/EBU digital audio signals. The
DAA-3400 will operate at any frequency from 34 to 54 KHz and may be used with non-EAS digital signals that have
net zero DC content. Provision is made for 75 ohm coax and 110 ohm balanced line in the input and output
distribution circuits. The DAA-3400 is designed to fit the IRT range of eurocard mounting frames, including the 12
slot FR-700 and 2 slot FRU-1030 rack mounting frames.
Circuit Description.
The DAA-3400 input circuit is a linking arrangement (SW1,SW2) to select either the balanced or unbalanced input
from the rear panel input connector. The signal is then coupled to a high speed differential line receiver using
transformer T1. The line receiver is buffered by its internal line driver circuit and this signal drives output line driver
circuits for the nine outputs from the DAA-3400, eight to the rear panel assembly via transformers T2-T9 and one
via T10 to the front panel monitor connector. The eight outputs to the rear panel are sourced through 51 ohms
resistors to set the output impedance for the balanced out put circuits when using the ZAA-3401 rear panel assembly.
For 75 ohms output circuits the ZAA-3400 rear panel assembly uses a resistive voltage divider to set the output
impedance back to 75 ohms at a nominal level of 1 Vp-p.
The power supply comprises two bridge rectifiers whose rectified outputs are paralleled (positive and negative
respectively) to provide redundancy. The inputs to these rectifiers are two independent feeds of 28 Vac (centre tap
grounded). A DC-DC converter module is used to provide the required 5 volts supply for the line receiver and
transmitter circuits. The DC indicator LED on the front panel is used to indicate presence of the 5 volts supply.
IRT
Communications
www.irtcommunications.com