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MAINTENANCE ORBAN MODEL 8685
Field Audit of Performance
Required Equipment:
• Bitstream analyzer that can accept AES3id inputs
Audio Precision System 2
Stanford Research Systems SR1
NTI Digilyzer DL1 or equivalent
• Digital voltmeter (for testing power supply voltages)
Accurate to ±0.1%.
• Oscilloscope
DC-coupled, triggered sweep, with 5MHz or greater vertical bandwidth.
• Two short 75Ω jumper cables terminated by male BNC connectors
• One 75Ω BNC “Tee” connector, male to two females.
• Optional: Distortion analyzer with analog input (for checking the performance
of the analog outputs)
Audio Precision System 2 or equivalent
• Optional: Two 620Ω ±5% resistors (for terminating the analog outputs)
• Optional: HD-SDI test set
Phabrix SxA AES or equivalent
It is assumed that the technician is thoroughly familiar with the operation of this
equipment.
This procedure is useful for detecting and diagnosing problems with the 8685's per-
formance. It assesses the performance of the digital inputs, digital outputs, and digi-
tal-to-analog converters and verifies that the digital signal processing section (DSP)
is passing signal correctly. If it is doing so, there is a high probability that the DSP is
performing the dynamic signal processing correctly. There is therefore no need to
measure such things as attack and release times—these are defined by software and
will automatically be correct if the DSP is otherwise operating normally.
If you do not have a signal analyzer with a digital input (like the Audio Precision Sys-
tem 2), you may use the 8685’s two analog outputs to drive an analyzer with analog
inputs. However, this will limit the resolution of your measurements.
The procedure uses the 8685’s built-in high-resolution sinewave oscillator to gener-
ate test tones. An external tone generator is not required.
It is often more convenient to make measurements on the bench away from high RF
fields which could affect results. For example, in a high RF field it is very difficult to
accurately measure the very low THD produced by a properly operating 8685 at
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