Residential Audio & Video Systems Copyright © 2005 Heathkit Company, Inc. All Rights Reserved Presentation 6 – The Spectrum Analyzer

2 Objectives At the end of this presentation, you will be able to:

3 Explain the difference between a time domain and a frequency domain display. Describe what the spectrum analyzer displays. Recognize the difference between linear and logarithmic scales. Define spectrum, harmonic, roll-off, white noise, and pink noise. Explain the purpose of an audio equalizer.

4 TIME/ DIV ms us.1.2 TR INTENS. FOCUS POWER X - Y Y-POS. IY-POS. II INVERT CH. I VERT. INP. 10M TRIG. I/II CHOP mV V VOLTS/ DIV mV V VOLTS/ DIV. 20 CH I/II DUAL ADD DC AC GD DC AC GD 20 MHz Dual Trace Oscilloscope X-MAG X 10 CH. II VERT. INP. 10M VAR. GAIN CAL. TV SEP. OFF TV: H TV: V TRIG. AC DC HF LF ~ X-POS. HOLD OFF. + / - EXT. AT/NORM. LEVEL TRIG. INP. 100Vp max CAL. Time Amplitude The Oscilloscope

5 Time Amplitude Time Domain Display

6 Fourier Theorem Any periodic waveform is made up of one or more sine waves that are harmonically related. A fundamental sine wave and a number of its harmonics can be combined to form any complex waveform.

7 Square Wave Sine Wave Odd Harmonics 3rd5th7th9th

8 Oscilloscope

9 Spectrum Analyzer Oscilloscope

10 Frequency Amplitude Frequency Domain Display

11 Frequency (kHz)

12 Spectrum Analyzer Oscilloscope

13 Linear Display 2kHz

14 1 Hz 10 Hz 100 Hz1 kHz 10 kHz Logarithmic Display

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16

17 Linear Logarithmic

18 The Spectrum Analyzer FREQ/ DIV Hz kHz TR INTENS. FOCUS POWER Y-POS Log LIN mV V VOLTS/dB/ DIV. 20 Audio Spectrum Analyzer X-MAG X 10 INPUT 10M VAR. GAIN CAL. X-POS. HOLD OFF. CAL. Volts dB Log LIN Freq Amplitude

19 20 K 70dB RangeLevel ENTERMODE Input

20 To Parallel Port

21

22 Controls Frequency Range Amplitude Log - Linear

23 Residential Audio System Amplifier System Tape Player Radio Other CD Player

24 Sources of Predictably Signals Audio Test CD Audio Test Cassette Tape Signal Generators

25 Signal Generator Produces Sine waves Square waves Saw tooth waves White noise Pink noise

26

27 20 Hz 60 Hz

28 20 Hz Odd Harmonics ALL Harmonics

29 White Noise A spectrum of frequencies across the entire band. Specific frequencies vary from one instant to the next. However, over time, all frequencies have about the same amplitude.

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31

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34 Pink Noise Start with white noise. Attenuate the frequencies at a precise rate. (Usually, 3 dB per octave)

35 The Audio Equalizer FADER k2k 4k 8k16k -12 OnOff EQ Bypass XOVER Level Frequency

36 FADER k2k 4k 8k16k -12 OnOff EQ Bypass XOVER Level Frequency 20 K 70dB RangeLevel ENTERMODE Input

Residential Audio & Video Systems Copyright © 2005 Heathkit Company, Inc. All Rights Reserved End