经典AudioPrecision音频分析仪测试介绍.ppt

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AP introduction
• XLR Connector
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AP introduction
• XLR Connector - In reference to its original manufacturer, James H. Cannon, founder of Cannon Electric in Los Angeles, California (now part of ITT Corporation), the connector is colloquially known as a cannon plug or cannon connector. - The most common is the 3-pin XLR3, used almost universally as a balanced audio connector for high quality microphones and connections between equipment. - XLR plugs and sockets are used mostly in professional audio and video electronics cabling applications. Home audio and video electronics normally use RCA connectors.
AP Introduction & THD + N
• Analyzer input and XLR connector • AP Panel • Audio specifications • THD + N
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AP introduction
• Analyzer input cable connection - Single ended output (MP3 headphone) 2 – Signal, 3 – Ground. e.g., Channel A: 2 – Left output, 3 – Ground Channel B: 2 – Right output, 3 – Ground - Differential output (loudspeaker) 2 – Non-inverting signal, 3 – Inverting signal
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AP introduction
• Crosstalk - Signals from one channel leaking into another channel. Normally, this happens between left and right stereo channels. - A generator drives one channel and this channel's output value is noted; meanwhile the other channel is set for zero volts. The measured channel left open. - Whatever signal is induced into the tested channel is measured at its output with an rms voltmeter and noted. A ratio is formed by dividing the unwanted signal by the abovenoted output test value, and the answer expressed in dB.
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AP introduction
• Signal to Noise Ratio - Signal to noise ratio, as a relative measurement, must be made with reference to a specific output amplitude from the device under test. - The rated output amplitude must be calibrated as the 0 dBr reference of the analyzer. Then the residual output amplitude (noise) is measured and expressed in dB relative to the reference.
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AP introduction
• Frequency Response - Frequency Response measurements are made by stepping or sweeping a sine wave oscillator, at a fixed amplitude, across the spectrum of interest. - Usually stated in terms of dB variation from some reference midband frequency(e.g., 1KHz). - The test may be easily modified. The frequency range and direction of sweep can be changed from the 20 KHz ~ 20 Hz stored by entering new values for START and STOP under SWEEP (F9) DEFINITIONS panel.
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• AP1 Panel
AP introduction
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AP introduction
• THD + N vs Level Curve
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AP introduction
• Analyzer Panel
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AP introduction
• Sweep Definitions Panel