The difference between constant resistance power amplifier and constant voltage power amplifier

The difference between constant resistance power amplifier and constant voltage power amplifier

The power amplifiers and speakers of the public address are of constant voltage, and the speaker  of the sound reinforcement system of the conference room are all of constant resistance, so what is the difference between constant resistance and constant voltage?

What they have in common: Both can amplify audio signals from computers, CDs, DVDs, etc., and promote the work of speakers.

- Each feature -

Constant voltage power amplifier

Constant voltage power amplifiers (amplifiers) are output at high voltage, most of which are monophonic settings, and the final output is generally output with an output transformer, the sound quality is slightly worse, but the transmission distance is long. Widely used in places with large spaces such as troops, railway stations, docks, schools, shopping malls, etc.

1. It is mostly used in public places.

2. Mono output.

3. High voltage and low current output.

Constant voltage power amplifiers are mainly used in public broadcasting and background music in public places. Because the distance between the public address and background music system speakers and the power amplifier is relatively long, and a power amplifier usually needs to be connected to multiple low-power speakers. In order to reduce line loss and prevent the volume of other speakers from being affected by the opening or closing of a certain speaker in the system, the constant voltage power amplifier outputs high voltage and low current (relatively). To connect multiple speakers of the power amplifier with constant voltage, just connect the speakers in parallel on an ordinary wire.

Fixed resistance power amplifier

Although the fixed resistance power amplifier has good sound quality, the transmission distance is short. Mainly used in family, KTV, conference hall.

1. It is mostly used in home theater, KTV, stage and conference room.

2. Stereo output.

3. Low voltage and high current output

Because speakers in conference rooms and stages are relatively close to power amplifiers and there is no need to connect many speakers, fixed-impedance power amplifiers output high current and low voltage, and special audio cables are used to connect power amplifiers and speakers.

- The difference between the two in the output form -

constant pressure

The output voltage does not change with the change of the load impedance, that is, the power amplifier with a constant maximum voltage of the output audio signal. Due to the use of deep negative feedback, the amount of this deep negative feedback is generally above 10~20dB, and the output voltage is very stable. The amount of load connected within the rated power range has little effect on the output voltage of the amplifier. In order to reduce the power loss of the transmission line in long-distance power transmission, an output transformer is needed. The higher the voltage, the smaller the loss of the transmission line.

The output voltage mainly includes 70V, 90V, 120V, etc. It requires a certain rated voltage of the load, and the constant-voltage power amplifier is connected in parallel with multiple constant-voltage speakers, and the power does not exceed the total power of the constant-voltage power amplifier.

In a constant voltage power amplifier, if the rated load voltage changes, the power will change accordingly. 100V, 10W speakers connected to 70V become 5W (the power difference between 100V and 70V is twice).

Fixed resistance

The power amplifier requires a certain output load resistance. If the load impedance changes in the fixed resistance power amplifier, the power will change accordingly. An 8 ohm 100W fixed resistance power amplifier connected to 4 ohms becomes close to 200W.