Amplifiers

An amplifier has one job: take a signal of about two volts and give it enough current to move a speaker cone. Everything else — the phono stage, the DAC, the Bluetooth, the tone controls — is a convenience bolted onto that. Which is why the specification that decides an amplifier purchase is not the one on the front of the box.

The wattage number is mostly theatre

Power buys volume very slowly. Doubling the watts adds 3 dB. Perceived “twice as loud” is roughly 10 dB, which needs ten times the power. So the difference between a 35-watt amplifier and an 85-watt one is under 4 dB — real, but far less than the numbers suggest.

Meanwhile the difference between two speakers can easily be 7 dB, which is a factor of five in power. Your speakers decide your volume; your amplifier mostly decides whether they misbehave. That is why our matching guide is the most important page in this hub, and why we would rather you read it before any of the roundups.

The specification games worth knowing

Dynamic power is not RMS power.Yamaha’s A-S501 is rated at 85 W + 85 W into 8 ohms across the full 20 Hz–20 kHz band at 0.019% THD. That is a real, hard rating. Search for its 4-ohm power, though, and you will find “185 W” everywhere — which is Yamaha’s published High Dynamic Power, a short-burst measurement. Yamaha publishes no continuous 4-ohm rating at all. Treating the dynamic figure as continuous overstates the amplifier roughly two-fold.

Conditions are the specification.Denon rates the PMA-600NE at 45 W into 8 ohms across the full band at 0.07% THD — and at 70 W into 4 ohms at 1 kHz and 0.7% THD. Both are Denon’s figures and both are honest, but they are measured under completely different conditions and reading them as a straight comparison is a mistake. Marantz publishes both of the PM6007’s figures under the same full-band condition, which is why it ranks so well with us despite publishing less power than the Yamaha.

A wattage with no conditions is not a specification. The Fosi V3 advertises 300 W × 2 at about $110. That figure is into 4 ohms, has no THD condition attached, and depends on which power supply you feed it — Fosi publishes an input range of 24–48 V. They publish no 8-ohm rating at all. It is a genuinely useful little amplifier and an object lesson in reading fine print.

Integrated, receiver, or separates

An integrated amplifier is a preamp and a power amp in one box. A stereo receiver is an integrated with a radio tuner added — the Sony STR-DH190 is one. If you will never use the tuner it is weight and cost doing nothing, which is a reasonable argument against it and not much more.

Separates — a preamp and a power amp in different boxes — buy you flexibility and cost you money and shelf space. At this budget we do not think it is the right trade for most people, and we do not currently cover it.

Note that several integrated amplifiers already contain a DAC. The Yamaha A-S301, Denon PMA-600NE and Marantz PM6007 all publish optical and coaxial inputs. If yours does, buying a separate DAC is buying a second one.

The Valve half of the name

We do not yet have a tube amplifier roundup, and we would rather tell you why than leave a suspicious gap on the hub named after them. We could not verify a set of tube amplifiers as currently purchasable through the retailer we link to, at prices that make sense, with published specifications we could actually read. When we can, we will build it.

In the meantime, tube versus solid state covers what genuinely differs — including the output-impedance mechanism that explains why a tube amplifier measures differently on different speakers — and where we have to stop, because we have not heard any of it.

One practical note while you shop: search for “tube amp” and most results are guitar equipment, where distortion is the goal rather than the problem. Search “tube integrated amplifier” instead.

What we would skip

Buying power you have computed you do not need. Run the arithmetic on your actual speakers at your actual listening distance. If you clear 95 dB with headroom — and most pairings do — spend the difference on the speakers, because that is where the audible difference lives.