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Power Amps

Behringer KM 750 750W Stereo Power Amplifier
400W Stereo / ATR Technology
£ 137.00
To Product
Behringer NX3000D
Lightweight 3000W Class D
£ 248.00
To Product
Fame Audio PA Patch Panel
4x Speakon I/O, 2x XLR I/O
£ 54.00
To Product

Power amplifiers form the backbone of the PA system - because as amplifiers they provide the necessary volume. Read everything you need to know before buying here!

1. PA Power Amplifiers – General Information 

4-Kanal-Endstufe von Fame Audio
4- Channel power amplifier from Fame Audio

In small set-ups, separate power amplifiers are less common because active speakers with integrated amplifiers are increasingly used. However, such active systems are simply too weak for events of a certain size. But even beyond that, dedicated PA power amplifiers offer some advantages. 

Advantages of separate power amplifiers:

  • Highest possible performance
  • Flexible combination with boxes and other components

Most power amplifiers are designed as 2-channel or 4-channel models. Apart from that, there are power amplifiers with DSP, which contain special functions such as equaliser, delay, crossover and limiter in digital form. Power amplifier cables are designed for connection to either Speak-on and terminals (output) or XLR, jack or cinch (inputs) - although of course not every amplifier has the same connections. 

Well-known PA power amplifier manufacturers include:

Behringer KM 750 Stereo Power Amplifier
Behringer KM 750 Stereo Power Amplifier with various connection possibilities.

2. Amplifier Classes

Amplifiers or power amplifiers are divided into classes, with Class-AB and Class-D being particularly relevant for PA power amplifiers, as well as Class-H in some cases. What does this mean?

Well, class A amplifiers can deliver high sound quality, but they are not exactly efficient in terms of heat and energy consumption. Class B power amplifiers are much more economical in terms of power consumption, but you have to make concessions in terms of sound, because distortion occurs more quickly. Class AB power amplifiers provide a remedy here by combining both properties - clean sound and efficiency. A further development of the AB principle is the Class-H.

Class-D power amp technology is not only efficient but also significantly more compact than units in other classes. Digital power amplifiers often feature such a Class-D design. 

Yamaha PX3 mit Class-D-Technologie
Yamaha PX3 with Class-D Technology

3. Power

Probably the most common question when it comes to PA power amplifiers is: How many watts do I need? This is not so easy to answer in a general way, because of course the required power of the amplifier always depends on the type and location of the event. As a general rule, it is better to have excess wattage than too little - you can always turn down the volume of a PA system; conversely, with weaker systems, the end is reached when a certain volume is achieved. 

As a rough example, one could say that for small evening events, an amplifier with 100 to 200 watts can be sufficient. (Rock) bands, on the other hand, should aim for power amplifiers in the mid three-digit watt range, and in the club environment and on larger stages, amplifiers with 1000 or (significantly) more watts are often used.

Tip: Don't forget the speakers in terms of power. A 2000-watt amplifier is of no use if the speakers cannot even come close to handling this power or volume.

A few rules of thumb for choosing the right power amplifier: 

  1. Rule: The entire PA system, including speakers and power amplifier, should have enough power so that you do not have to push it to the limit. If in doubt, go for a higher power category.
  2. Rule: The power amplifier should have a little more power than the speakers. If the amplifier is always driven at its load limit, resulting in overdriving/distortion/clipping, this can damage the speakers.
  3. Rule: Always use the RMS value to compare the power of the amplifier and the speaker. Other values are usually inaccurate and cannot be compared well. Also pay attention to how the values turn out with different resistance (Ohm).

4. Switching power supply vs. conventional power supply

Switching power supplies are often the first choice in professional power amplifiers: They are smaller and lighter than conventional power supplies, but at the same time offer better energy economy thanks to higher efficiency. Conventional power supplies are primarily cheaper - still a small advantage, even if less relevant in the professional PA sector.

5. Cooling

Rückseite der QSC PLD 4.2 mit eingebautem Lüfter
Rear of the QSC PLD 4.2 with integrated fan.

You have already read above that power amplifiers produce heat - logical, after all, there is a lot of power involved. To prevent the unit from stuttering or, in the worst case, giving up completely, PA power amplifiers are equipped with cooling mechanisms. There are two main variants here:

  • Active cooling by means of a fans
  • Passive cooling through air circulation

Active cooling provides more reliable results in almost all cases and is recommended especially in professional, demanding environments. 

Tip: Look for dust filters in the power amplifier housing and also clean the unit from time to time. This will ensure that there is always sufficient air flow.

6. Protection mechanisms

When using a PA power amplifier, many things can go wrong, from unsightly clipping to destruction of the equipment. To prevent this as far as possible, a good power amplifier should have appropriate protective mechanisms. These include, for example: 

  • Overheating protection
  • Limiter
  • DC protection circuit (DC voltage protection)
  • Overload protection