Crown_Com-Tech_00_Series_Reference_Manual电路图.pdf

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1、K80636-2 3/95 Commercial Audio LL 32521C Fire Protective Signaling S5206 Commercial Audio E106377 120 VAC North American Units: Approved for THX Theatre Systems (CT-400 R = 0.016 ohms or D.F. = 500; Cable Length = 10 ft.; answer: #8 wire LS 1 0.5 200 500 1,000 2,000 20,000 5,000 10,000 .01 .001 .02

2、.004 .006 .002 .0004 .0006 .0002 0.6 0.7 0.8 1.5 0.9 tion 4.1, Precautions. You should always install loudspeaker cables of suffi- cient gauge (wire thickness) for the length used. The resistance introduced by inadequate output cables will reduce the amplifiers power to and motion control of the lou

3、dspeakers. The latter problem occurs be- cause the damping factor decreases as the cable re- sistance increases. This is very important because the amplifiers excellent damping factor can be easily ne- gated by using insufficient cable. Use the nomograph in Figure 3.13 and the following procedure to

4、 find the recommended wire gauge (AWG or American Wire Gauge) for your system. 1. Note the load resistance of the loudspeakers con- nected to each channel of the amplifier. If you are using 70 volt output, be sure to determine the load resistance of the step-down transformers (Crowns constant voltag

5、e computer can help with this, see Section 8.3). Mark this value on the “Load Resistance” line of the nomograph. 2. Select an acceptable damping factor and mark it on the “Damping Factor” line. Your amplifier can provide an excellent damping factor of 1,000 from 10 to 400 Hz in Stereo mode with an 8

6、 ohm load. In contrast, typical damping factors are 50 or lower. Higher damping factors yield lower distortion and greater motion control over the loudspeakers. A common damping factor for commercial applications is between 50 and 100. Higher damping fac- tors may be desirable for live sound, but lo

7、ng cable lengths often limit the highest damping factor that can be achieved practically. (Under these circumstances, Crowns IQ System is often used so amplifiers can be eas- ily monitored and controlled when they are located very near the loudspeakers.) In recording studios and home hi-fi, a dampin

8、g factor of 500 or more is very desirable. Use Good Connectors 1. To prevent possible short circuits, do not expose the loudspeaker cable connectors. 2. Do not use connectors that might acciden- tally tie two channels together when making or breaking connections (for example, a stan- dard three-wire

9、 stereo phone plug). 3. Connectors that can be plugged into AC power receptacles should never be used. 4. Connectors with low current-carrying ca- pacity should not be used. 5. Connectors with any tendency to short should never be used. 3. Draw a line through the two points with a pencil, and contin

10、ue until it intersects the “Source Resistance” line. 4. On the “2-Cond. Cable” line, mark the length of the cable run. 5. Draw a pencil line from the mark on the “Source Resis- tance” line through the mark on the “2-Cond. Cable” line, and on to intersect the “Annealed Copper Wire” line. 6. The requi

11、red wire gauge for the selected wire length and Fig. 3.13 Wire Size Nomograph Page 20 Com-Tech 200/400/800/1600 Power Amplifiers damping factor is the value on the “Annealed Copper Wire” line. Note: Wire size increases as the AWG gets smaller. 7. If the size of the cable exceeds what you want to use

12、, (1) find a way to use shorter cables, like using the IQ System, (2) settle for a lower damping factor, or (3) use more than one cable for each line. Options 1 and 2 will require the sub- stitution of new values for cable length or damping factor in the nomograph. For option 3, estimate the effecti

13、ve wire gauge by subtracting 3 from the apparent wire gauge every time the number of conductors of equal gauge is doubled. So, if #10 wire is too large, two #13 wires can be substituted, or four #16 wires can be used for the same effect. SOLVING OUTPUT PROBLEMS High-frequency oscillations can cause

14、your amplifier to prematurely activate its protection circuitry. The effects of this problem are similar to the RF problems described in Section 3.3.2. To prevent high-frequency oscillations, follow these guidelines: 1. Bundle together each pair of loudspeaker conduc- tors when using long cable runs

15、 or when different amplifiers use a common cable tray or jacket. (Do NOT bundle wires from different amplifiers.) This reduces the chance of conductors acting like antennas to transmit or receive the high frequen- cies that can cause oscillation. 2. Avoid using shielded loudspeaker cable. 3. Never t

16、ie together input and output grounds. 4. Never tie together the output of different amplifiers. 5. Keep output cables separated from input cables. 6. Install a low-pass filter in series with each input (see Section 3.3.2). 7. Install the input wiring according to the instructions in Section 3.3.2. A

17、nother problem to avoid is the presence of large sub- sonic currents when primarily inductive loads are used. Examples of inductive loads are 70 volt trans- formers and electrostatic loudspeakers. Inductive loads can appear as a short circuit at low fre- quencies. This can cause the amplifier to pro

18、duce large low-frequency currents and activate its protec- tion circuitry. Always take the precaution of installing a high-pass filter in series with the amplifiers input when inductive loads are used. A three-pole, 18 dB per oc- tave filter with a 3 dB frequency of 50 Hz is recom- mended (some appl

19、ications may benefit from an even higher 3 dB frequency). Such a filter is described with subsonic frequency problems in Section 3.3.2. Another way to protect inductive loads from large low- frequency currents and prevent the amplifier from pre- maturely activating its protective systems is to paral

20、lel a 590 to 708 F nonpolarized motor start capacitor and a 4 ohm, 20 watt resistor in series with the amplifier output and the positive (+) transformer lead. This cir- cuit is shown in Figure 3.14. It uses components that are available from most electrical supply stores. 3.3.4 Additional Load Prote

21、ction Com-Tech amplifiers can generate enormous power output. Using 8/4 ohm output, if your loudspeakers do not have built-in protection from excessive power, its a good idea to protect them. Loudspeakers are subject to thermal damage from sustained overpowering and Fig. 3.15 Loudspeaker Fuse Nomogr

22、aphFig. 3.14 Inductive Load (Transformer) Network 4 ohm, 20 watt Resistor 590 to 708 f Capacitor 120 VAC, N.P. + Inductive Load + From Amplifier Output 1.0 1.2 1.4 1.6 2.5 3 4 5 6 7 8 9 10 12 14 16 20 25 30 20 15 10 8 6 5 4 3 2 1.5 1 .8 .6 .5 .4 .3 .2 .15 .1 .08 3000 2000 1500 1000 800 600 400 300 2

23、00 150 100 80 60 40 30 20 15 10 8 6 4 3 2 1.5 1 SPEAKER Z (ohms) FUSE (amps) SPEAKER RATING PEAK MUSIC POWER (watts) (Typically 4 times the continuous average power) Example: Z = 8 ohms. Peak Power = 75 W Answer: Fuse = 1.5 A 2 40 Page 21 Com-Tech 200/400/800/1600 Power Amplifiers mechanical damage

24、from large transient voltages. In both cases, special fuses may be used to protect your loudspeakers, or you may opt for the convenience of a P.I.P. module that provides loudspeaker protection. Two different types of fuses are required for thermal protection and voltage protection. Slow-blow fuses a

25、re usually selected to protect loudspeakers from thermal damage because they are similar to loudspeakers in the way they respond to thermal conditions over time. In contrast, high-speed instrument fuses like the Littlefuse 361000 series are used to protect loud- speakers from large transient voltage

26、s. The nomo- graph in Figure 3.15 can be used to select the properly rated fuse for either type of loudspeaker protection. There are mainly two different approaches used when installing fuses for loudspeaker protection. A common practice is to put a single fuse in series with the output of each chan

27、nel. This makes installation easy because there is only one fuse per channel to install, but it can also lead to problems. The biggest disadvantage be- comes apparent if the fuse blows because power to all connected loads will be removed. A better approach is to fuse each driver indepen- dently. Thi

28、s allows you to apply the most appropriate protection for the type of driver being used. In general, low-frequency drivers (woofers) are most susceptible to thermal damage and high-frequency drivers (tweet- ers) are usually damaged by large transient voltages. This means that your loudspeakers will

29、tend to have better protection when the woofers are protected by slow-blow fuses and high-frequency drivers are pro- tected by high-speed instrument fuses. Depending on the application, you may want to use a P.I.P. module to protect your loudspeakers. When properly configured, all P.I.P. modules wit

30、h signal- driven compression can provide loudspeaker protec- tion. Some of the P.I.P. modules with signal-driven compression include the P.I.P.-AMCb, P.I.P.-EDCb and P.I.P.-PA. While the P.I.P.-EDCb is most commonly used for general loudspeaker protection, the P.I.P.- AMCb is very popular in systems

31、 that require a high- quality crossover, and the P.I.P.-PA is the processor of choice for applications that require a microphone and line level input for each channel. For more information on P.I.P. modules, see Section 8. 3.4 AC Mains Power All 120 VAC, 60 Hz North American units have a NEMA 5-15 A

32、C plug with an integral voltage presence lamp. These units include a 16 gauge cord with Com-Tech 200s and 400s, and a 14 gauge cord with Com-Tech 800s and 1600s. Other Com-Tech amplifiers are fur- nished with an appropriate AC cord and plug. Use an isolated wall outlet whenever possible with the cor

33、rect voltage and adequate current. Voltages greater than 10% above the specified AC mains volt- age for the amplifier may damage the 15 volt regula- tor, filter capacitors and output transistors. See Section 7 for power requirements under various conditions. All specifications in this manual were me

34、asured using 120 VAC, 60 Hz power mains unless otherwise noted. Specifications are derived using a mains voltage that is accurate to within 0.5% with THD less than 1.0% un- der all testing conditions. Performance variations can occur at other AC voltages and line frequencies. In ad- dition, line reg

35、ulation problems will directly affect the output power available from the amplifier. Page 22 Com-Tech 200/400/800/1600 Power Amplifiers 4 Operation 4.1 Precautions Although your amplifier is protected from internal and external faults, you should still take the following pre- cautions for optimum pe

36、rformance and safety: 1. Improper wiring for the Dual, Bridge-Mono and Parallel-Mono modes, as well as the 8/4 ohm and 70 volt output modes can result in serious operating difficulties. Refer to Section 3.3.1 for details. 2. WARNING: Never attempt to operate the amplifier in either Bridge-Mono or Pa

37、rallel-Mono mode unless both output channels are configured the same (8/4 ohm or 70 volt). 3. When driving an inductive load (like a 70 volt step- down transformer) use a high-pass filter or protec- tive network to prevent premature activation of the amplifiers protection circuitry (see Section 3.3.

38、3). 4. WARNING: Do not change the position of the dual/ mono switch or the output mode switches unless the amplifier is first turned off. 5. CAUTION: In Parallel-Mono mode, a jumper must be installed between the channel 1 and 2 positive (+) output terminals. Be sure to remove this jumper for Dual or

39、 Bridge-Mono modes, otherwise high distor- tion and excessive heating will occur. Check the dual/mono switch on the back panel for proper position. 6. Turn off the amplifier and unplug it from the AC mains before removing a P.I.P. card or before removing the dust filter. 7. Use care when making conn

40、ections, selecting sig- nal sources and controlling the output level. The load you save may be your own! 8. Do not short the ground lead of an output cable to the input signal ground. This may form a ground loop and cause oscillations. 9. Operate the amplifier from AC mains of not more than 10% abov

41、e or below the selected line voltage and only the specified line frequency. 10. Never connect the output to a power supply output, battery or power main. Such connections may result in electrical shock. 11. Tampering with the circuitry by unqualified person- nel, or making unauthorized circuit chang

42、es may be hazardous and invalidates all agency listings. Remember: Crown is not liable for damage that results from overdriving other system components. 4.2 Indicators The front panel of a Com-Tech amplifier has several helpful indicators. The amber Enable indicator is pro- vided to show the amplifi

43、er has been turned on (or en- abled) and that its low-voltage power supply is working. It does not indicate the status of the high-volt- age power supplies. For example, the Enable indicator will remain lit in the unlikely event that one of the amplifiers protection systems (described in Sec- tion 4

44、.3) removes power from one (or both) high-volt- age supplies to put the channel in “standby” mode. The Enable indicator will be illuminated for all condi- tions shown in Figure 4.1 except for the first example, “There is no power to the amplifier. ” The green ODEP indicators confirm the normal opera

45、- tion of Crowns patented Output Device Emulation Pro- tection circuitry. During normal operation, they glow brightly to confirm the presence of reserve thermal-dy- namic energy. They dim proportionally as the energy reserve decreases. In the rare event that there is no reserve, the indicators will

46、turn off and ODEP will pro- portionally limit the drive level of the output stages so the amplifier can continue safe operation even when conditions are severe. (For a more detailed description of ODEP, see Section 4.3.1.) A channels ODEP indicator also turns off if its high- voltage power supply is

47、 put in “standby” mode or the amplifiers circuit breaker is tripped. The standby mode is activated if DC or heavy common-mode cur- rent is detected at the output, if the transformer thermal protection system is activated, or if a P.I.P. like the P.I.P.-UL1711 or the IQ-P.I.P. is used to shut down a

48、high-voltage power supply. (For more information, see Section 4.3.3 and the table in Figure 4.1.) The yellow IOC indicators act as sensitive distortion meters to provide proof of distortion-free performance. The IOC (Input/Output Comparator) circuitry com- pares the incoming signals waveform to that

49、 of the output. Any difference between the two is distortion. The IOC indicators flash if there is a difference of 0.05% or more. It is normal for them to light momen- tarily when the amplifier is first turned on. Note: the channel 2 IOC indicator will stay on in Parallel-Mono mode. The green Signal Presence Indicators (SPI) flash syn- chronously with the output audio. The SPI detector cir- cuit is connected in the signal path after the input gain stages and level controls, so a flashing indicator tells you that there is audio in and out of the amplifier. Note: The Signal Presence Indic