Telos Zephyr, User Manual

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Section 11 TECHNICAL INFORMATION 217
There are four major sections of the AES/EBU card:
1. The AES/EBU interface circuitry: U9 and U5 (CS8411) are AES/EBU receivers which
translate AES/EBU signals into the more useful three signal digital interface (clock,
data, frame- sync). U4 (CS8401) is the AES/EBU transmitter chip which generates
the AES/EBU compatible signal from the 3- wire interface. Both the receivers and
the transmitter are separated from the
outside world by transformers (T1- T4).
2. The Sample Rate Conversion circuitry: U1, U2, U3, and U6 (AD1890/1) convert the
sample rates of digital audio signals from the AES/EBU signals to the those used
internally by the Zephyr, and vice- versa. The chips can be placed in the audio path
or removed as needed through the control circuitry.
3.
The Control Circuitry: U7 (PAL26V12) is used to allow the Zephyr to address the
Xilinx chip (LCA1) and the AES/EBU chips. It generates the appropriate chip select
signals for each chip according to where it is located in Zephyr memory. LCA1 is
responsible for routing the sample rate converter chips into and out of the digital
audio chain. This is accomplished by a series of switches inside the chip which are
addressed individually by the Zephyr microprocessor. In addition, the 11.28MHz
crystal is routed through the Xilinx chip to provide the 44.1kHz sampling rate not
normally supported by the Zephyr.
Connector Descriptions
1. AES- IN: This is the XLR connector for the AES/EBU input from a digital audio
source. The Zephyr can automatically adjust the sample of the incoming signal to
match the internal Zephyr clocks, or this function can be bypassed if the AES/EBU
signal is already synchronized to the digital network.
2.
AES- OUT: This connector is used to provide the AES/EBU output signal from the
Zephyr receive path. The audio is identical to the Zephyr analog output, but the
sample rate is programmable.
3.
SYNC- IN: This is used to provide an external AES/EBU signal which the Zephyr can
then be synchronized to. Primarily for studios with a master clock, this connector
accepts any AES/EBU signal, and uses only the clock.
4. SYNC- OUT: An AES/EBU output that is simply the SYNC- IN routed back to the
outside world. This is useful in daisy- chaining several AES/EBU compatible devices
with one SYNC signal.
Power Supply
The power supply has a universal AC input, accepting a continuous input range
of 100- 240VAC, 50/60Hz. Its outputs provides three separate voltages: a +5V supply
which powers all the digital circuits, a ±12V output supplies basic audio circuits and is
further regulated on the motherboard to ±5V for critical audio functions like the A/D
and D/A sections. A separate small linear regulator supplies the critical PLL power.