Audio Adapter+ Reference Manual

The Audio Adapter+ is a module that provides easy audio connectivity to the Analog Discovery 3. It is equipped with Mono and Stereo 3.5 mm audio connectors that provide signal paths to both the inputs of the oscilloscope and outputs of the arbitrary waveform generator. The Audio Adapter+ is equipped with a 2×15 MTE connector, which makes it compatible with the Analog Discovery 3, in addition to the Analog Discovery (Legacy), and Analog Discovery 2. An additional 2×15 MTE connector is loaded as a pass-through for digital signals, power supplies, and trigger pins so that these features are fully supported for your audio applications.

• Provides audio connectivity via 3.5 mm jacks for both Scope inputs and Wavegen outputs
• Inputs and outputs can independently use 2 mono jacks or 1 stereo jack, selected via jumpers
• Active circuitry powered by the Analog Discovery 3 power supplies
• Pass-through Connector for all other Analog Discovery 3 signals, including Digital I/O, Triggers, and Power Supplies
• Compatible with the Analog Discovery 3, Analog Discovery 2, and Analog Discovery (Legacy)

The Audio Adapter+ is compatible with the following:

• Analog Discovery 3
• Analog Discovery 2
• Analog Discovery (Legacy)

This reference manual applies to Revision C of the Audio Adapter+.

Table 1: Connectors and Jumpers

Warning: Please be careful when connecting a stereo audio source to mono connectors as it will short the second channel to ground. This may lead to damaging your audio equipment if it's not protected.

The Audio Adapter+ can be used to acquire audio signals generated by other devices. The audio inputs make use of Scope input channels, and can make use of any WaveForms instruments that leverage these hardware resources, like the Oscilloscope, Spectrum Analyzer, and Network Analyzer instruments. Scope inputs can be used simultaneously alongside AWG outputs and other I/O.

The adapter can process either stereo or mono audio signals passed in through the 3.5 mm audio input jacks, J1 and J2. The Mono/Stereo input connector (J1) can be used with either mono or stereo inputs. The Mono-only input connector (J2) can only be used with mono inputs and is only active when the adapter is being used in mono mode. In order to select the input type, JP1 should be placed in the desired position.

The equivalent circuits for the Mono and Stereo audio input modes are summarized in the circuit diagrams, below:

The Audio Adapter+ can be used to generate audio signals. The audio outputs make use of AWG output channels and can make use of any WaveForms instrument that can leverage these hardware resources, like the Wavegen, Network Analyzer, and Impedance Analyzer instruments. AWG outputs can be used simultaneously alongside Scope inputs and other I/O.

The adapter can generate signals for both stereo and mono audio cables and devices, via the 3.5 mm audio output jacks, J3 and J4. The Mono/Stereo output connector (J3) can be used with either mono or stereo outputs. The Mono-only output connector (J4) can only be used with mono outputs and is only active when the adapter is being used in mono mode. In order to select the input type, JP2 should be placed in the desired position.

An active amplifier circuit is used to condition AWG output signals prior to sending them out over audio output jacks. This means that voltage levels displayed in the Wavegen instrument in WaveForms are not necessarily representative of the amplitude of a signal on an actual audio cable. For more information, check out the “Amplifier” section, below.

The equivalent circuits for the Mono and Stereo audio output modes are summarized in the circuit diagrams, below:

The audio outputs go through a voltage divider and an amplifier, which are used to scale down the output range from -5 to 5 V to between -1 and 1 V, in order to protect external audio equipment from inadvertent damage. The gain between the AWG output and the audio connector is roughly 1/5.

The amplifier requires power from the Analog Discovery's power supplies in order to function. While the Audio Adapter+ is in use, see the Power section, below.

The gain from each AWG output to the Audio jack is roughly:

$$V_{Audio}={V_{AWG} \over 5}\label{1}\tag{1}$$

As such, the audio signal range is:

$$-909mV < V_{Audio} < 909mV \left( High\;Range \right)$$ $$-227mV < V_{Audio} < 227mV \left( Low\;Range \right)\label{2}\tag{2}$$

The analog output signals are AC coupled. The common mode voltage of the amplifier is set to 0 V, which means that any DC offset applied to the AWG output is effectively removed when it reaches the audio connector.

For a detailed circuit diagram of the analog output amplifier circuitry, refer to the Audio Adapter+ Schematics

In order to function properly, the Audio Adapter+ must be provided with power from the Analog Discovery 3 power supplies. Active circuitry is used in the output amplifier and should be provided power through the use of the Power Supplies instrument in WaveForms. The Power Supplies should provide 1.5 V or greater through the positive supply rail, with tracking enabled to provide -1.5 V or the equivalent through the negative rail.

The Analog Discovery Audio Adapter is controlled with the Analog Discovery 3 through the use of WaveForms.

• For more information on the Audio Adapter+ and Analog Discovery 3, check out their resource centers: Audio Adapter+, Analog Discovery 3
• WaveForms can be downloaded from the WaveForms Resource Center.
• Audio Adapter Schematics