Tech Talk Application Note #5
Tech Talk Application Note #5
Application: Using the AES-302 Digital Audio Switcher/DA with an inexpensive CD/DVD Player
to provide automatic back up audio at a transmitter site for stations lacking an alternate path.
Benefits: Interfacing the AES-302 to an inexpensive CD/DVD Player capable of MP3 playback
provides hours of playback audio at very little cost. The cost of the player used in this example was
less than fifty dollars.
Application Note: The accompanying schematic diagrams on page 3 show the suggested connection of remote control interface and digital audio connection between the BDI AES-302 and a CD/
DVD player with coaxial digital output. Audio connection is taken from the coaxial output of the
player and connected to the B input of the AES-302. If a player with optical output is available, the
AES-302 can be ordered with an optical input for direct connection via a light pipe. It is necessary to
modify the player by soldering a pair of wires to the start button of the machine. A player with a
wired remote could also be used. Choose a CD/DVD player that is suitable for your needs. If you
will be recording MP3 files make sure that the recording CD player and the CD/DVD player that you
use for this project are compatible with each other. Also, choose a player that will remain on at all
times. Some players go to “sleep” after a certain amount of time. Players suitable for this project can
be had for as little as $50.00 making this an inexpensive and easy way to provide many hours of
automatic backup audio for a station.
The photos on the next page show how a simple circuit board with DIP relay, resistor, and capacitor can be mounted right inside the player. If you have a player that can be started with a maintained
closure, the capacitor and resistor aren’t needed. Simply connect pin 7 to the relay coil. We used a
DB9 connector for interface but a ¼” or 1/8” tip/ring/sleave phone jack and plug could be used as
there are only two remote connections from the AES-302 required. Use the tip and ring for connections to the circuit and add a ground to the sleave if desired. If a DB9 is used, the additional relay
contacts could be used to actuate an alarm or auto dialer.
Here is how it works: If your primary feed were to fail, the AES-302 will switch immediately or
after predetermined silence depending on the type of failure. Once the AES-302 switches to the B
input, the remote control status output will command the CD/DVD player to start playing. Depending on the your recording sample rate and amount of compression, the CD player can provide many
hours of playback audio to your transmitter pending restoration of the primary feed. For example, at
128 kB/sec can provide over ten hours of back up audio with this simple and inexpensive setup. BDI
can supply the parts necessary for this example or a wired perforated board with components
mounted. Call us for availability.
For any questions about this application or any other, feel free to call or email us for further information. Telephone – (914) 737-5032 or email us at Techsupport@Broadcast-Devices.com
You can install the suggested circuit
inside the player. Here we used a DB9
connector for connection and support.
You can use a simple 1/4” or 1/8” tip/
ring/sleave phone jack instead as the
project only requires two connections
to the AES-302.
Figure 1
Figure 2 shows a simple two wire
solder connection two the front
panel start button. These are the
only connections to the player.
The AES-302 provides power and
ground. The on board relay
provides a dry closure to the
player.
Figure 2
Here a rear panel view shows the DB9
connector protruding from the back. Allow
enough clearance so that the cover can be
replaced and that nothing touches inside.
The player in this example has plenty of
room inside so the board could have been
mounted to the chassis as an alternate
method.
Figure 3
Tech Talk Application Note
www.Broadcast-Devices.com (914) 737-5032
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AES-302 REMOTE
CONTROL
DB9F
1
A Input of AES-302
4
B Input of AES-302
4
2
2
1
1
D
3
3
1
6
2
8
3
7
4
9
5
D
A Command to R/C
B Command to R/C
R/C Cont/Status Common
A Selected Status Out to R/C
C
C
CD/DVD Player
+
R1
100K 1/4W
C1
4.7uF/25V
K
Coaxial Digital Output RCA JACK
SW
SW PUSHBUTTON Inside Player
If unbalanced cable is used connect shield to pins 1
and 3 of the XLR connector.If balanced cable is
used, connect the center pin of the RCA plug to pin
2 of the XLR and connect the other balanced wire
to the shield and then connect the shield to pins 1
and 3 of the XLR connector as shown.
12 VDC DPDT
B
B
Suggested Digital Audio Cable and Remote
Control Wiring Between Player and
AES-302
BDI Tech Talk Application Note
A
A
AES-302 Application 5
AES-302/CD/DVD Interface
Call BDI Applications Engineering at (914) 737-5032 or email to:
TechSupport@Broadcast-Devices.com
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