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Resumen del manual
The lower the am: -’s output impedance, the fa;- :.he overshoot of the voice < ! dampen out. The output h ce of an amplifier can be lated by dividing the rated ut impedance, typically : us, by the damping factor. Tj 4B has a damping factor of 200 which correspond: n output impedance of 0.04 3.5.1 Calculi g the Maximun ngth of Cable fo : Specified ALTEC LANSING* CORPORATION ® a Mark IV Company 3 Operating and Service Instructions for the Altec Lansing 9444B Power Amplifier Table I 9444B Power Losses in 2-wire Speaker Cable Power Cable Cross- Power Awa DCR/ft Loss/ft Sect ional DCR/nietcr Loss/moii (GA) (-O/ft) (watWft) area (mm*) (ft/m) (watts/m 6 0.00081 0.0201 13.30 0.00264 0.0661 8 0.00X21 0.0302 8.36 0.00421 0.1051 10 0.00204 0.0509 5.26 0.00669 0.1669 12 0.00324 0.0809 3.31 0.01063 0.2650 14 0.00515 0.1286 2.08 0.01691 0.4210 16 0.00819 0.2043 1.31 0.02685 0.6667 18 0.01302 0.3244 0.82 0.04289 1.0609 20 0.02070 0.5148 0.52 0.06764 1.6627 22 0.03292 0.8163 0.33 0.10658 2.5950 Damping Factor Specification at the Load The damping factor rating is typically never realized at the load because of the resistance of the cable (and other factors such as the contact resistance of an output relay or the resistance of an output fuse). The damping factor at the load should be 30 for general paging systems and 50 for high fidelity music systems. Economics usually dictate, however, that these numbers are cut-in-half. The resulting damping factor at the load should be based on experience and customer satisfaction. Once a minimum damping factor is determined for a particular type of instaDation, the following equation can calculate the maximum length of 2-wire cable which can be used to achieve the minimum dam ping factor specified at the load: Max. Length of 2-wire cable in feet ZL. — Zo = _JDF_ DCR/ft where ZL is the load impedance to connect to the amplifier; Zo is the amplifier’s output impedance (0.04 ohms for the 9444B); DF is the minimum permissible damping factor at the load; and DCR/ft is the DC resistance of the 2-wire cable per foot from Table I. The same equation can be used to calculate the maximum cable length in meters by substituting the DCR per meter value from Table I. Let’s use the equation. Suppose ZL equals 8 ohms, Zo = 0.04 ohms, and the minimum damping factor at the load is 25. In addition, 18 GA cable is preferred. Then, the maximum length of 18 GA cable which can be used to achieve a damping factor of 25 at the load is: 8 — (0.04) _25_ = 21.5 feet 0.01302 f>/ft Sometimes it may be necessary to locate the speaker 100 feet or more away from the amplifier. In this situation, a much larger gauge cable is required. However, this may not be practical or economical. The size of the 2-wire cable can be greatly reduced by stepping up the output voltage of the amplifier to 70, 100, 140, or 210 volt, using an output transformer, then stepping down the voltage at the load. Such a system is shown in Figure 5. The maximum length of 2-wire cable in this situation can be approximated from the following equation: Max. Length of 2-wire cable in feet V8 _1___Zo_ (Pout)(DCR/ft) DF ZL where V is the stepped-up age of the system; Pout is the rated out,., power of the amplifi Zo is the output im ance of the amplifier ohms for the 9444B . ZL is the load impeda DCR/ft is the DC tance of the 2-wire per foot from Table I: DF is the minimum missible damping faci the load. Suppose a 210 volt system v. used at a 600 watt power lev-; drive an 8 ohm load with an n: mum damping factor of 25. Us -I the same 18 GA cable as bet the maximum length can nov. 198 feet. Power companies this technique to transfer ler amounts of power over great tances. 3.6 Speaker Protect: Fuse Selection Sometimes it may be ci< irable to use in-line fuses (fuse series with the output) to pro;-loudspeaker systems (or the a: lifier). It is difficult, however, determine the proper fuse va! with the correct time lag a:; overload characteristics to mat the limitations of a speaker sy tem. The values shown in Table I should serve only as a guide. 4 ALTEC LANSING* CORPORATION • a Mark IV Company Operating and Service Instructions for the Altec Lansing 9444B Power Amplifier INPUT POWER AMPLIFIER STEP-UP TRANSFORMES 70. 100. 140, OR 210 VOLTS LONG CABLE RUN (SHALL GAUGE WIRE) LOUDSPEAKER STEP-DOWN TRANSFORMER Figure 5 High-voltage Distribution System use, determine the power rating and load value. Then, select a standard value fuse of the next smaller value to the one listed Ln the table. Table II Calculated Output Fuse Values Power 4 ft 8ft 16 ft (wutis) Load Load Lead 100 3-70 2.62 1.85 150 4.54 3.21 2.27 200 5.24 3.70 2.62 300 6.42 4.54 3.21 -100 7.41 5.24 3.70 600 9.07 6.42 4.54 The values are calculated for fast-blow fuses which carry 135% of their current rating for an hour but will blow within 1 second at 200%. Other fuse values may be calculated for different power levels from the fol...
Otros modelos de este manual:El receptor y el amplificador - 9444B (926.12 kb)