Power amplifier technology
Power amplifier type characteristics:
Thinuna offer several series of amplifiers, these amplifiers are carefully designed and meet international standards. All models are designed with perfect protection circuits to ensure long life and trouble-free operation. Also greatly reduce the amount of repair, reduce maintenance and use costs. There are the following categories:
Combined amplifier
Single-channel pure post-stage power amplifier
Combined amplifier with partition
Dual-channel pure post-stage power amplifier
combined amplifier with partition and each partition ca independently adjust the volume
High impedance constant voltage connections and low impedance constantresistance connections.
Broadcast amplifier usually adopts 100V/70V line output voltage to push the speaker. The low voltage power signal output from the amplifieris converted to 100V line high voltage power signal by the transformer inside the amplifier, and then input to the broadcasting loudspeaker through the transmission line, which is converted to low voltage by the matching transformer built in the broadcasting loudspeaker and pushes the loudspeaker to sound. When the transmission distance of broadcasting system is long, the transmission voltage can be increased to reduce the loss caused by line transmission, and there is no need to use heavy low-resistance cable to make the transmission distance longer.
Broadcast speakers(be conn ected in parallel to the 100V/70V circuit of the fixed-voltage amplifier. As long as the rated output power of the amplifier is not exceeded, any number of speakers can be connected (when the line is too long, the same need to allow for the loss caused by the line); considering that low-impedance connections need to consider impedance matching, in order to avoid wrong connections, PA systems should use high-impedance (fixed-voltage) connections if possible.
In addition to the 100V/70V fixed voltage output, the broadcast amplifier usually also has a low e connection output such as 4 ohm/8 ohm/16 ohm. The total inputim nedance ofthe speaker must be designed to be greater than the output impedance of the amplifier in the low-impedance connection. If the total impedance of the speaker is lower than that of the amplifier, it may lead to unstable operation or amplifier failure. Constantresistance output amplifier and speaker wiring distance should be less than a few dozen meters, such as wiring distance is too long, the amplifier output power will be consumed -part in the cable heat and can not provide adequate power to the speaker.
Example of fixed voltage connection: The PA-6250 is a 500W power amplifier that can drive a total of 25 20W bi-directional projection speakers, HW-220B, using 100V output. Since the transformer of HW-220 projection speaker provides three power selection taps, full, half and 1/4 power. When each speaker is connected to the half power tap, the output power of the speaker is 10W, and the number of speakers that can be accessed by the amplifier is doubled to 50; when each speaker is connected to the 1/4 power tap, the output power of the speaker is 5W, and the number of speakers that can be accessed by the amplifier is 4 times 100.
The same reason for the amplifier output: if the amplifier output is changed from 100V output to 70V output, the speaker can only provide half power output, so the number of speakers can be doubled. Similarly, the number of speakers that can be connected to the 50V amplifier output compared to the 100V amplifier output is 4 times, but the output power of each speaker is only 1/4 of the rated power.
It can be seen that: when the PA-6250 fixed-voltage amplifier uses 70V output, while the HW-220B speaker is connected to 1/4 power tap, the number of speakers that can be connected at this time is 2x4= 8 times, and the speaker output power is 1/8 rated power 2.5W.
Output cable selection: the cable cross-sectional area connecting the speakers should not be less than 0.5 square millimeters, the material shouldbe 600V vinyl (PVC) insulated wire, preferably with flame retardant materials, with twisted wire is preferred (good anti-interference effect), the cable should be arranged in the pipe slot, or take other effective protection measures and shielding.
The size of the cable cross-sectional area depends on two factors:
The size of the load power (the higher the power, the thicker the cable should be)
The distance of transmission (the longer the distance, the thicker the cable should be)
Cross-sectional area of broadcast cable versus transmission distance and load power:
The data in the table below comes from the assumption that all speaker loads are placed at the farthest endof the cable, which allows the cable cross-sectional area to be reduced if the speakers are arranged evenly along the transmission cable. Therefore, the cable cross-sectional area selected for practical applications is usually smaller than the values in the table below.
