Dynamic Headroom

It refers to the ability of an amplifier to deliver a greater amount of power on brief musical peaks than the amount of power it is rated to deliver continuously.

That can be good in the sense that the peak power levels required by a lot of music can be vastly higher than the average levels that are required. Classical symphonic music is one of the most extreme examples of that.

However, high dynamic headroom can also be an indication that the amplifier's power supply and/or its thermal design are "weak," because it indicates that the amplifier cannot sustain its maximum power capability for very long.

Regards,
-- Al

Almarg...I don't agree with your description of the power supply as "weak". It may have been designed that way.

I like to think about this issue in terms of voltage. The amplifier delivers an electrical output which is the same shape as the input signal, but at higher voltage. When the output voltage is applied to a load (speaker) current will be drawn, and if the amp can't deliver enough current the voltage will fall. This limits amp power. Amp power may be limited by either the voltage it can output, or the current it can supply. It is better to be limited by current because music typically includes voltage peaks of such short duration that the power supply can provide the necessary current for a brief interval by drawing from its capacitance.

The "continuous rms power" by which audio amps are rated is really unsuitable for audio. The "headroom" measurement is important.

You also asked what the numbers mean. 3 db of headroom means that it has headroom that allows the amp to double its output for short periods of time.

I also disagree with Almarg about "signs of a weak power supply". The rest of the info is good.