Why it matters
Class decides efficiency, heat, size, and power supply needs — not whether an amp “sounds good.” For a DIY or battery build, that efficiency number drives the whole design: heatsinks, enclosure, and run time.
How it works
The class is about how much of each signal cycle the output devices are switched on:
- Class A conducts the whole cycle. Very linear, but it burns power as heat even at idle, so it is hot, heavy, and rare in DIY power amps.
- Class AB conducts a bit more than half each, with two halves handing over near zero. It is the long-standing linear compromise — good performance, moderate efficiency, needs real heatsinking. Common in older and audiophile gear.
- Class D switches the output fully on and off at a high rate, then filters the result back to audio. Efficiency is typically 85–95%, so it runs cool and small. It dominates subwoofer plate amps, portable speakers, and most modern builds.
Class D is not “digital” — it is a switching analog amplifier. Modern Class D measures excellently and is the default choice for almost any DIY build that cares about heat, size, or battery life.
Common mistakes
Simple example
Related concepts
Related concepts
Discussion
No discussion yet
Ask a question or share a field note tied to this topic — it shows up here.