Read the power specification, not the number
The Marantz PM6007 is rated at 45 W per channel into 8 ohms, 20 Hz to 20 kHz. The Fosi Audio V3 advertises 300 W x2. Those figures describe different things.
The Marantz specification states the impedance, the frequency range across which the power is delivered, and implies a low distortion figure. It is a continuous RMS rating: the amplifier can produce that power all day, at every frequency, into that load. Class-D wattage claims across the budget market are typically quoted at peak, into an unstated load, at a distortion level far above what anyone would want to listen to, and often at a single frequency.
The practical consequence: judge a budget class-D amplifier by whether it drives your speakers to the volume you want without strain — which the Fosi units comfortably do with any speaker on our bookshelf list — and judge an integrated amplifier by its stated specification. Don’t compare the two numbers directly, because they are not the same measurement.
How much power do you actually need?
Less than the marketing implies. Loudness scales logarithmically: doubling amplifier power buys about 3 dB, which is a just-noticeable step up in volume, not twice as loud.
- Sensitive speakers (89-91 dB), a normal room: 20-30 W is genuinely enough. The Klipsch R-40M at 91 dB will go louder than most people want on a Fosi V3.
- Average speakers (85-87 dB): 40-60 W gives comfortable headroom.
- Insensitive speakers or a large room: this is where a 100 W receiver like the Sony earns its rating.
More common than an underpowered amplifier is an overdriven one: a small amplifier pushed into clipping produces distortion that can damage tweeters. Headroom protects speakers rather than threatening them.
The phono input question, in order
- Does your turntable have a built-in preamp?Most decks under $400 do, usually with a PHONO/LINE switch on the back. If yes, any amplifier here works — use a line input and leave the deck on LINE.
- If not, does the amplifier have a phono input? The Sony STR-DH190, Denon PMA-600NE and Marantz PM6007 do. That is one box and one purchase fewer.
- If neither, buy a phono stage. See under $100 or under $200.
One rule that catches people constantly: never run two phono stages in series. A turntable with its internal preamp switched on, plugged into a phono input, produces distorted, painfully loud sound. Switch one of them off.
Receiver or integrated amplifier?
A stereo receiver like the Sony STR-DH190 is an integrated amplifier plus a radio tuner and usually more input switching. An integrated amplifier like the Denon or Marantz drops the tuner and spends the money on the amplification and the power supply.
At the same price, the integrated amplifier generally sounds better because more of the budget went into the parts that matter. At different prices, the receiver often wins on value: the Sony includes a phono input, four line inputs, Bluetooth, A/B speaker switching and FM for less than an entry integrated costs. For a first vinyl system it is very hard to argue against.
What the expensive amplifiers actually add
Between the Fosi V3 and the Marantz PM6007 there is a large price gap. What it buys, in rough order of audibility:
- A better power supply. Large transformers and reservoir capacitors let an amplifier deliver current on demand during loud passages instead of sagging. This is where most of the money in a good integrated goes and it is the least visible line item.
- A better phono stage. The Marantz uses a FET input stage for its MM phono input; budget amplifiers with phono inputs typically use the cheapest circuit that works.
- Analog isolation. The Denon lets you power down its digital section entirely, removing a real noise source from a phono signal measured in thousandths of a volt.
- Build and longevity. A well-made integrated amplifier is a twenty-year purchase. A $90 class-D box with an external wall supply is not necessarily.
Where an amplifier upgrade sits in the queue
Honestly? Behind speakers, behind cartridge, and behind setup. Amplifiers operating within their comfortable power range and not clipping sound more alike than any other component category. If you are choosing between a $600 amplifier with $200 speakers and a $200 amplifier with $600 speakers, take the second one every time.
Buy up in amplifiers when you need a specific feature — a phono input, Bluetooth, enough power for insensitive speakers, or A/B switching for two pairs — or when you have already spent well on speakers and want the amplifier to stop being the ceiling.
