Related Manuals for CBS laboratories Audimax 4450
Summary of Contents for CBS laboratories Audimax 4450
- Page 1 CBS Audimax 4450 Installation, Operation, and Maintenance CBS Laboratories Professional Products Stamford, Connecticut 06905...
- Page 2 Installation, Operation, and Maintenance Manual This manual is based on the CBS Laboratories manual, “CBS Audimax Models 4440A, 4450A Au- tomatic Level Control—Operating and Maintenance Instructions,” produced by the Professional Products Division, CBS Laboratories, Stamford, Connecticut 06905, August 1972. Copyright CBS...
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Page 3: Table Of Contents
CBS Audimax 4450A Automatic Level Control Table of Contents 1 General Description Introduction Functional Description Physical Description Specifications 2 Installation Procedures Signal Connections 3 Operational Setup Gated Gain Stabilizer Test Switch Decay (Recovery) Time Switch 4 Principles of Operation Overall System Operation Circuit Description 4.2.1 Gated Gain Stabilizer 4.2.2 Functional Graphs... - Page 4 Table 3.1 GGS Threshold Values for Table 3.2 Decay Time Settings Table 4.1a Parts List for the Audimax 4450 Input/Output Board Table 4.1b Parts List for the Audimax 4450 Power Supply/Logic Board Table 4.1c Parts List for the Audimax 4450 Chassis...
- Page 5 Trace 5.1 Audimax 4450 frequency response. The left channel is shown in blue, the right channel is shown in green. 35 Trace 5.2 Audimax 4450 THD+N. The left channel is shown in blue, the right channel is shown in green. 35 Trace 5.3 Audimax 4450 input/output phase (left channel).
- Page 6 Installation, Operation, and Maintenance Manual...
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Page 7: General Description
(Source: CBS Labs.) Introduction The Audimax 4450A, like the CBS Laboratories Volumax companion unit, is a tool to help the broadcaster achieve maximum audio program power within appropriate modulation limits. Designed for use wherever high-quality automatic-gain control is necessary, the 4450 provides a unique means of audio-signal control for AM, FM, and TV broadcasting, sound recording, motion-picture sound, and public address systems. -
Page 8: Specifications
The third board contains the Audimax dc power supply and the remainder of the audio feedback and logic circuitry. Specifications Typical specifications for the CBS Audimax 4450 are given in Table 1.1. Table 1.1 Specifications for the Auximax 4450 Parameter... -
Page 9: Installation Procedures
CBS Audimax 4450 Automatic Level Control Installation Procedures The Audimax 4450 is designed to be mounted in a standard 19-inch electronic equipment rack or 19-inch-wide console opening. The mounting dimensions are shown in Figure 2.1. Install the unit in a reasonably well-ventilated position, making sure there is no high-heat producing equipment located beneath it. - Page 10 Installation, Operation, and Maintenance Manual, Installation Procedures Figure 2.1 Installation guidelines for the Audimax 4450. (Source: CBS Labs.)
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Page 11: Operational Setup
8 VU with normal program input. With both CONTROL switches ON, adjust the left and right OUTPUT controls as needed to produce the desired output levels. With proper levels out of the audio console, the Audimax 4450 can operate without additional adjustment on the part of the operator. -
Page 12: Gated Gain Stabilizer
Installation, Operation, and Maintenance Manual, Operational Setup Figure 3.1 Front panel layout of the Audimax 4450. (Source: CBS Labs.) Gated Gain Stabilizer The function of the Audimax Gated Gain Stabilizer (GGS) is to answer the following question: Should the gain be increased when a lapse occurs in the audio program? This is especially important for television and motion pictures where the lapses occur quite often. -
Page 13: Test Switch
Decay (Recovery) Time Switch The gain control action of the Audimax 4450 has been designed to provide a precise degree of control with a minimum of noticeable change in the short-term dynamic range. As a tool for the broadcaster, the unit provides maximum modulation consistent with artistically acceptable performance for a wide variety of program material. - Page 14 Installation, Operation, and Maintenance Manual, Operational Setup...
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Page 15: Principles Of Operation
CBS Audimax 4450 Automatic Level Control Principles of Operation An overall block diagram of the Audimax 4450 is shown in Figure 4.1. The monaural model (4440) consists of the same input/output, feedback, and logic circuits, but without an input/output board for the right channel. - Page 16 Installation, Operation, and Maintenance Manual, Principles of Operation Figure 4.1 Audimax 4450 overall block diagram. (Source: CBS Labs.)
- Page 17 CBS Audimax 4450 Automatic Level Control Figure 4.2 Audimax 4450 system interconnections. (Source: CBS Labs.)
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Page 18: Circuit Description
20 seconds and the system gain is less than 0 dB, the gain will, similarly, return to 0 dB. These return-to-zero functions place the Audimax 4450 in a proper standby condition for the reappearance of audio signals after a program pause. - Page 19 CBS Audimax 4450 Automatic Level Control Figure 4.3 Schematic diagram of the audio input/output board ( ). (Source: CBS Labs.)
- Page 20 Installation, Operation, and Maintenance Manual, Principles of Operation Figure 4.4 Circuit board layout of the audio input/output board ( ). (Source: CBS Labs.)
- Page 21 CBS Audimax 4450 Automatic Level Control Figure 4.5 Schematic diagram of the power supply/logic board ( ). (Source: CBS Labs.)
- Page 22 Installation, Operation, and Maintenance Manual, Principles of Operation Figure 4.6 Circuit board layout of the power supply/logic board ( ). (Source: CBS Labs.)
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Page 23: Gated Gain Stabilizer
4.2.1 Gated Gain Stabilizer GGS action is employed to prevent the Audimax 4450 from seeking its maximum gain during a lapse of audio greater than approximately 2 seconds. For this discussion, a “lapse of audio” refers to a condition wherein the input signal level is below the GGS threshold. Referring to Figure 4.3,... - Page 24 Installation, Operation, and Maintenance Manual, Principles of Operation Figure 4.7 Audimax 4450 gain characteristic curves. (Source: CBS Labs.) level is smoothly increased from –50 dBm to –15 dBm, and then back down to –50 dBm. As the input is increased from –40 dBm to about –35 dBm, the gain of the device is constant because, although rectifier 2 has developed about –3 volts, the output from rectifier 1 is zero.
- Page 25 CBS Audimax 4450 Automatic Level Control Figure 4.7e –15 dBm to –20 dBm, the gain remains constant along NP. The output follows the line CD; the control voltage to remains constant along HK while the output of rectifier 2 drops along A1Q27 As the input level is reduced below –20 dBm, however, the output of rectifier 2 becomes less...
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Page 26: Power Supply
4.2.3 Power Supply The regulated power supply in the Audimax 4450 provides +20 V dc and –15 V dc. The schematic diagram of the regulated power supply is shown in Figure 4.5. Regulation is used to prevent variations in the ac line input from affecting Audimax circuit operation. Line voltage is... -
Page 27: Parts List
This preservation of balance in both amplitude and phase is vital when broadcasting stereo programming. Parts List The parts for the Audimax 4450 is given in Table 4.1. Table 4.1a Parts List for the Audimax 4450 Input/Output Board Component Number Description μ... -
Page 28: Table 4.1B Parts List For The Audimax 4450 Power Supply/Logic Board
910 k, 1/4 W R83, R84 240 ohms, 1/4 W 8.2 k, 1/4 W 6.2 k, 1/4 W Table 4.1b Parts List for the Audimax 4450 Power Supply/Logic Board Component Number Description μ C1, C2, C3, C4, C5, C6 F, 50 V electrolytic μ... -
Page 29: Table 4.1C Parts List For The Audimax 4450 Chassis
CBS Audimax 4450 Automatic Level Control Table 4.1b Parts List for the Audimax 4450 Power Supply/Logic Board 5 k, variable, linear (not used) R101 (memory unit) 1.2 megohms, 1/4 W R102 (memory unit) 510 k, 1/4 W Diode, zener, 15 V, 1N4744A Diode, zener, 20 v, 1N4747A Table 4.1c Parts List for the Audimax 4450 Chassis... - Page 30 Installation, Operation, and Maintenance Manual, Principles of Operation...
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Page 31: Maintenance And Adjustments
CBS Audimax 4450 Automatic Level Control Maintenance and Adjustments Remove all power from the Audimax 4450 prior to performing maintenance. For certain adjustments and troubleshooting, it will be necessary to operate the unit with power on. Observe proper safety precautions at all times. -
Page 32: Troubleshooting Suggestions
26) Alignment is now complete. Remove the test equipment and reassembly the unit. Troubleshooting Suggestions Troubleshooting of any apparent malfunction of the Audimax 4450 should begin with a check of the power supply. The dc voltages indicated at the power supply test points on board should fall within the tolerances indicated on the schematic diagram. -
Page 33: Input/Output Circuits
CBS Audimax 4450 Automatic Level Control supply could cause to fail. Similarly, shorting of the –15 V dc supply could cause A2Q2 A2Ql fail. The +20 V supply has a normal ripple value of 1 mV p-p; for the –15 V supply ripple is typically 2 mV rms. -
Page 34: Measured Performance
Trace 5.3 shows phase shift from input to output on the left channel as a function of frequency. Trace 5.4 shows the interchannel (left vs. right) phase shift through the Audimax 4450. This parameter is not specified by the manufacturer. - Page 35 Trace 5.1 Audimax 4450 frequency response. The left channel is shown in blue, the right channel is shown in green. Trace 5.2 Audimax 4450 THD+N. The left channel is shown in blue, the right channel is shown in green. Trace 5.5 shows left/right channel separation across the audio frequency band. This parameter is not specified by the manufacturer.
- Page 36 Installation, Operation, and Maintenance Manual, Maintenance and Adjustments Trace 5.3 Audimax 4450 input/output phase shift (left channel). Trace 5.4 Audimax 4450 interchannel phase shift. -100 Trace 5.5 Audimax 4450 crosstalk. The left channel is shown in blue, the right channel is shown in green.