What it does
A power amplifier takes the small, finished signal from a preamplifier and delivers the current and voltage needed to move loudspeaker drivers. It has no volume control and usually no source selection; it is fed by a preamplifier, a streaming preamplifier or a DAC with its own volume control. Because it is the component that works hardest, its design and its match to the loudspeaker have an outsized effect on dynamics, bass control and the sense of ease at volume.
The options
Stereo or monoblock
A stereo amplifier holds both channels in one chassis. Monoblocks use one chassis per channel, each with its own power supply, and can sit next to the loudspeaker on short cables. Monoblocks offer more isolation between channels and more room for heat sinks and transformers; a stereo amplifier is simpler to place and usually costs less for the same quality.
Watts and current
The watt rating tells you how loud an amplifier can play into an easy load. Current delivery tells you how well it copes with a hard one. Loudspeakers whose impedance dips low, or whose phase angle swings, need an amplifier that keeps its composure when the load gets difficult. This is why two amplifiers with the same rating can sound very different on the same loudspeaker.
Class A, AB and D
Class A amplifiers run their output devices fully on all the time. They are warm to the touch, limited in power for their size, and prized for their liquidity. Class AB designs, which include most McIntosh and Boulder amplifiers, run in class A at low levels and switch to a more efficient mode as demand rises. Class D uses high-speed switching to deliver a great deal of power from a small, cool chassis; the best modern examples are serious instruments.
Tube or solid-state
Tube power amplifiers from McIntosh and Audio Research trade some control and ultimate power for a sense of air and dimension that remains hard to duplicate. Solid-state amplifiers from Pass Labs, Boulder, Burmester and MOON deliver more power with less upkeep and, with the right loudspeaker, lose little in the way of beauty.
Bi-amping
Loudspeakers with two sets of binding posts can be driven by two amplifiers, one for the bass and one for the midrange and treble. Done carefully, with matched gain, it can unlock dynamics and clarity. Done carelessly, it is expensive. We are happy to talk through whether a particular loudspeaker rewards it.
How we think about it at Pearl
The amplifier is chosen for the loudspeaker, not the other way around. We carry power amplifiers from McIntosh, Pass Labs, Boulder, Burmester, Audio Research and MOON, which lets us offer tube and solid-state, stereo and monoblock, from under 100 watts to the McIntosh MC1.25KW and the Boulder 3050. Our two listening rooms let you hear how a loudspeaker responds to different amplifiers rather than take it on trust.
Where to start
Tell us what loudspeakers you own or are considering and how large the room is. If you already have a preamplifier, bring its model name too; gain structure matters. From there we can suggest two or three amplifiers and set up a comparison.
