Class-A amplifier
TL;DR
Class-A is the traditional analog amplifier topology where transistors conduct continuously. Legendary for smoothness and lack of crossover distortion but extremely inefficient (~25%) - burns hot and needs massive heatsinks.
Class-A amplifiers have transistors that conduct current continuously across the entire audio waveform. This eliminates crossover distortion (a nonlinearity where Class-AB transitions between transistor pairs) but at massive efficiency cost.
Trade-offs
- Pro: audibly smooth midrange, no crossover distortion
- Con: ~25% efficient – most power dissipated as heat
- Con: huge heatsinks, hot to touch, high power consumption
- Con: rarely delivers more than 20W per channel in reasonable form factors
Where you’ll find it
Rare in budget hi-fi due to cost and heat. Some tube preamps operate Class-A. Most modern budget amps use Class-D for efficiency or Class-AB for compromise.
Ready to see this in action?
Browse honest, hands-on reviews of budget hi-fi gear that puts these concepts to the test.
