© 2004 Wohler Technologies Inc. ALL rights reserved
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AMP2-DA/AVU and AMP2-DA/APP User Manual P/N 821584 Rev-A Section 3: Technical Information
AES to Analog Converter Module PCB (919117)
There are four primary and three ancillary sections comprising the 919117 PCB (AES/EBU digital to analog converter):
1) Input source selection.
2) audio data extraction.
3) Digital to analog conversion.
4) Analog buffer / output amplifiers.
5) Power suppy, Reset, and Error indication.
Input Source Selection (IC13)
Each of the two selectable signal inputs are transformer-coupled to the inputs of a one-of-two active buffer/switch (IC13). The output
of this switch is applied to the receiver stage of the AES receiver/unframer.
Audio Data Extraction (IC11)
"Header" and ancillary data are removed from the recovered input datastream, yielding a datastream having only alternating left/right
channel audio data, which is output on pin 26 of IC11.
Digital to Analog Conversion (IC10)
The "pure" audio datastream, along with a data clock and a channel ID (left/right) clock, are applied to a 20 bit two channel D to A
converter (IC10), where the datastream is converted into left and right analog outputs.
Analog buffer (IC4) / Output Amplifiers (IC8, IC9)
Buffer/amps provide balanced left and right channel outputs as well as single ended outputs. Gain calibration, the analog level, which
corresponds to a given digital value, is settable via a DIP switch. The default factory setting is 20 dB below "full code" (digital zero)
to equal +4 dbu (0.775V). The other three settings possible are for -18 dBfs = 0 dBu, -20 dBfs = 0 dBu, and -20 dBfs = +8 dBu.
See page 16 for DIP switch location and settings.
Power Supply
The 24V rail internal to the rest of the unit is converted to +5V for digital portions of the 919117 PCB by switching regulator IC12.
Error Indication
The AES status LED is a bicolor LED (Red/Green). It is green as long as a valid digital data strean is being received. The 8412 receiver
is capable of indicating two types of error conditions: 1) Faulty data; data identified by the sending device (possibly invalid), and 2)
Faulty reception; errors in reception of data or no data stream at all. A DIP switch on the rear panel (Item B, page 12) may be set to
allow the AES Status LED to indicate reception and data errors
or to indicate reception errors only.
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