Thomann's Cool Online Guides: PA-Amps

5. Technical Matters

Unfortunately, even the leading manufacturers of power amps have yet to make it easy for non-technical musicians to know what’s right for their needs. Here, we take a look at some of the terminology used and give you some idea of what it means, so you can be sure that you’re comparing like with like.


RMS stands for ‘Root Mean Square’ and is the official, international and only really meaningful indication of the power capacity of an amp. The RMS value of an amp is expressed in Watts (W) - 200 Watts RMS, 1 kilowatt RMS and so on (1 kilowatt (kW) = 1,000W, often referred to simply as ‘K’), and indicates that the amp will continuously maintain a stable, consistent signal across all frequency ranges, up to the specified power value. You should always consider buying an amp with a slightly higher RMS value than you need, so you can operate it comfortably within its specified range.

Sine Wave Power

Another measurement of power output and quality, largely superseded by RMS, but still used occasionally. If you come across it, it is broadly interchangeable with RMS, providing it is ‘Continuous’ Sine Wave Power.

Peak Power

Beware of this measure - it always looks higher than RMS, but it is only an indication of the maximum output capacity of the amp, or indeed the maximum loading of the speakers. It gives you no real indication of the amp’s ability to perform throughout its range or over time.

Peak Music Power Output (PMPO)

Again, a measure sometimes used to suggest more power than can realistically be delivered. Unlike RMS or Sine Wave Power, PMPO measures the power according to the varying frequencies of actual music playing through the system, and produces a measure of the maximum capacity. Like Peak Power, this measure is an absolute maximum, which may actually damage the system if it is sustained for any length of time. Approach this rating with caution - always use RMS or Sine Wave Power.

Rated Output

A measure used in the electrical industry that is occasionally applied to power amps. Broadly, it is similar to RMS, but since they do not use the same methods of calculation, it is not safe to directly compare the two.

Energy Dissipation

This is the measure of the amount of electricity that is converted to heat energy by the amp. The higher the value, the more cooling is required.


This is the electrical measure of resistance, measured in Ohms. It is a critical specification when matching amps and speakers. If there is a bad match, at best you’ll get a bad sound, at worst you’ll damage amp, speakers, or both. Note the following key considerations:

  • Low impedances place a heavier load on the amp, which will generate more heat. Make sure the cooling system is good enough, and allow for plenty of circulation.

  • Very low impedances may also overload the amp to the extent that its circuit protection kicks in an switches it off.

  • You need thicker and/or shorter cables when attaching low impedance speakers, because the quality of the signal deteriorates rapidly along longer cables.

  • Usually, higher impedances lead to better sound because they allow for easier matching of amps and speakers, although modern power amps are often capable of driving down to 2 Ohms.

Impedance essentially works like the narrowing of a stream of water - the higher the impedance, the narrower the gap, so it follows that an amplifier will deliver more power at lower impedances, and in fact their ratings are generally given at several different impedances, typically 16 Ohms, 8 Ohms, 4 Ohms and 2 Ohms. In short, always be careful that you are comparing apples with apples in terms of power and impedance, and that you are looking at the measurement per channel, not ‘bridged mono’ - some amplifiers are capable of joining both channels together to form a more powerful but single channel amp. Try to work within the maximums set out in the data sheets - just as you wouldn’t rev a car at its peak for long periods, so your power amp is not designed to work flat out continuously.

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PA-Amps overview

Alesis Surge Mesh Kit Adam T5V Subpac M2X Roland R-07 black Yamaha Stagepas 600BT Arturia Minibrute 2 Focal Listen Professional Heritage Audio HA-73 EQ Elite Epiphone Richie Faulkner Flying V Focal Shape Twin Sound Devices MixPre-3 Yamaha Stagepas 400BT
Alesis Surge Mesh Kit

E-Drum Set 385 Sounds, 40 kits, 60 songs, Additional input for a fourth tom and a second crash pad, 2 Master outputs 6.3 mm mono jack, Headphone output 3.5 mm stereo jack, Aux input 3.5mm stereo jack, MIDI input...

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Adam T5V

Active Nearfield Monitor Equipped with: 5" woofer and 1.9" U-ART ribbon tweeter, 2x Class-D amplifiers: 50W RMS woofer, 20W RMS tweeter, Frequency range: 45 - 25000 Hz, Crossover frequency: 3 kHz, Maximum input level: 106 dB (1m/pair), Rear bass...

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Subpac M2X

Subpac M2X, Mobile tactile bass system, SubPac adds real depth, connection and enjoyment to whatever you play through it - your music and media comes to life with the added dimension of physical bass. Frequency Response: 1hz-200hz, Wired Input: 3.5mm...

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Roland R-07 black

Portable MP3 / WAV Recorder with Bluetooth Functionality Stereo recordings up to 24 Bit / 96 kHz in WAV format or up to 396 kbps in MP3 format on microSD / SDHC card, Built-in stereo microphone, Integrated hybrid limiter,...

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Yamaha Stagepas 600BT

Mini-PA System with Bluetooth Function Consisting of 2x passive 2-way boxes and 10-channel power mixers, Power mixers and speaker cables can be stored in the boxes for transportation, Successor of the Stagepas 600i, Including 2 speaker cables, each 6...

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Arturia Minibrute 2

Arturia Minibrute 2; analog semi-modular Synthesizer; Combination of classic and modular Synthesizer; 25 note Keyboard with Aftertouch; Brute-Oscillator; Steiner-Parker-Filter; additional Loop-Envelope; linear FM; Hardsync; two free assignable LFOs; integrated Step Sequencer; Arpeggiator; 48 point Patchbay; Pitch- and Modulation Wheel; Connections:...

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Focal Listen Professional

Headphones Closed, Circumaural, Conversion technology for acoustic transparency and dynamics, Impedance: 32 ohms, Sensitivity (@ 1 kHz - / 1 Vrms): 122 dB SPL, THD (THD, @ 1 kHz / 100 dB SPL): 0.3%, Frequency range: 5 Hz to...

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Heritage Audio HA-73 EQ Elite

Heritage Audio HA-73 EQ Elite; 1-Channel Mic-Preamp wit EQ; based on the 1073; hand wound Carnhill Transformers; 3 stage fully discrete class A mic preamp; max. Gain: 80 dB Mic and 50 dB Line; -20 dB Pad; LO-Z switches the...

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Epiphone Richie Faulkner Flying V

Electric Guitar Body and neck: Mahogany, Fretboard: Ebony, Neck profile: Thin C, 22 Jumbo frets, Scale: 628 mm, Pickups: Active EMG 57 (bridge) and EMG 66 (neck) humbucker, Floyd Rose 1000, Grover Rotomatic machine heads, Colour: Black, Incl. Deluxe...

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Focal Shape Twin

Active Near Field Monitor Tweeter with low directivity for flexible listening position, Closed design with two passive membranes for easy installation near the wall, 2.5-Way concept for optimal control of the bass and lower mids, Optimal integration through extensive...

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Sound Devices MixPre-3

Sound Devices MixPre-3; portable audio recorder with USB audio interface; 5 tracks: stereo mix + 3 isolated tracks; Kashmir microphone preamp with 76db gain; equivalent Input Noise: 128dBu max (A-weighting, gain=76dB, 150 Ohm source impedance); limiter per channel; low cut...

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Yamaha Stagepas 400BT

Mini-PA System Bluetooth Function Consisting of 2x passive 2-way boxes and 8-channel power mixers, Power mixers and speaker cables can be stored in the boxes for transportation, Successor of the Stagepas 400i, Including 2 speaker cables, each 6 m...

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