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Balanced Audio Input Module

Transient, frequency, and noise analyses were performed on a PSpice model of the balanced audio input circuit. The first simulation run was a transient response simulation. Plotting the pair of input voltages (sine waves, inverses of each other) and the output voltage shows that the circuit does, indeed, properly receive a balanced audio input signal. Also shown is the gain feature of the trim stage of the circuit, here set to a gain of 4. Refer to the attached PSpice plot entitled balanced audio input - gain of 4. Since one stage of the input board is capacatively coupled to the next, to remove DC bias voltages, frequency response simulation was carried out, to ensure that the high-pass filter was designed properly. The specification for the mixer unit dictates that the unit be no more than 3dB down at 20Hz. The simulation shows that the low-end 3dB point of the input circuit is at around 17Hz. Refer to the attached plot, entitled balanced audio input frequency response. Lastly, an input noise analysis was run. This was done to gain data for later noise analysis. Unfortunately, at present, an NE5532 model for PSpice is nowhere to be found. This noise data is for the 741 op-amp. Still, it provides at least some indication as to the noise present. Further analysis will be done when the proper Spice model has been obtained. Refer to the attached plot, entitled balanced audio input, noise analysis.
next up previous contents
Next: Unbalanced Audio Input Up: Mixer Unit Previous: Mixer Unit   Contents
Steve Richardson 2000-07-06
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