Transistors
Solid-state amplifiers use transistors to increase the signal and drive the speakers. Size, heat and efficiency depend on the circuit, but they do not need routine tube replacement.
AMPLIFICATION
From a small signal to room-filling sound
An amplifier controls volume and supplies the power that moves the speakers. The choices below describe different parts of how it does that.
On this page
FROM CHOOSING TO DRIVING
Control first, power second
The control stage selects the source and sets the listening level. The power stage supplies the current that moves the speakers. An integrated amplifier combines both in one box; separates use a preamplifier and a power amplifier.
Source
Control
Power
Speakers
THE OUTPUT DEVICES
Tubes or transistors?
Vacuum tubes
Tube amplifiers use vacuum tubes (also called valves) to increase the signal. They may need periodic tube replacement and careful speaker matching.
HOW THE CIRCUIT WORKS
Circuit arrangement and amplifier class
These terms answer different questions. Tubes or transistors describe the devices. Single-ended or push-pull describes how output devices work together. Class A, AB or D describes how they operate—not a quality ranking.
Single-ended
One output device, or one group, handles the full waveform. Often simple and commonly associated with lower-powered tube designs.
Push-pull
Two halves of the output stage share the waveform. This can provide more power and better efficiency.
Class A, AB and D
In Class A, output devices conduct throughout the waveform. In Class AB, complementary devices share the waveform with some overlap. Class D uses rapid switching for high efficiency; the D does not mean “digital.”
MATCH THE WHOLE SYSTEM
Power, headroom and speakers
Watts are one clue
Current delivery, power supply and behaviour into changing speaker impedance also affect real-world control.
Sensitivity changes demand
More sensitive speakers need less power for the same volume. Room size and listening distance matter too.
Headroom keeps music open
Extra clean power helps short musical peaks arrive without strain.
Listen as a system
The best amplifier suits the speakers, room, sources and the way you actually listen.
CHOOSING WITH INTENTION
Questions worth answering first
- 01
Which speakers will the amplifier drive?
- 02
How far away do you sit, and how loudly do you like to listen?
- 03
Which sources need an input?
- 04
If you are considering tubes, are you comfortable replacing them occasionally?