This page lists American companies that build amplifiers, from multichannel power amps for home theater, stereo and whole-house audio to hand-built tube heads and combos for guitar and bass players.
An amplifier's sound and reliability come mostly from its power supply, transformers, circuit boards and tubes or output devices. The US makers here design their own circuits and build and test every amp themselves. Some parts are usually bought from other countries, such as Class D output modules, vacuum tubes and output transformers, and each listing names them when the company or another source says so.
For loudspeakers see Speakers, and for surround processors and preamps see Processors.
More types in this section ↓
ATI makes heavy-duty power amplifiers for home theater, stereo and multizone systems: the Signature Series AT6000 and AT4000 (Pure Balance current-feedback Class AB designs by Morris Kessler, 2 to 7 channels, up to 300 watts per channel), the AT3300 Pure Balance series (330 watts per channel, 2 to 8 channels), the AT1820 Class AB series (200 watts per channel, 2 to 7 channels), AT500NC Class D amps (200 or 500 watts per channel) and AT7012/AT7016 distribution amps that drive up to 16 speakers in 8 zones. All amplifiers are rated with every channel driven across the full 20 Hz to 20 kHz band, and most carry a 7-year parts and labor warranty. ATI is the parent company of Theta Digital.
Each channel gets its own transformer windings, rectifier and storage capacitors. The toroidal transformers use MOH cores with bifilar windings, the boards are double-sided FR-4 glass epoxy with 1% metal-film resistors, and the gold-plated RCA and XLR jacks mount to the chassis rather than the circuit board.
Made in: Los Angeles area, CA (every amplifier designed and assembled in its 50,000 sq ft factory, using a mix of hand-built and automated steps, with quality control, listening and performance testing; toroidal transformers wound by ATI).
Imported: the AT500NC Class D series uses Hypex Ncore output modules from the Netherlands, combined with ATI's own input stages and linear power supplies.
Source: ATI About Us · ATI Class D, 2026 · Sound & Vision, checked 10/2026
Montebello, CA
Mills Custom builds boutique guitar and bass amplifiers, speaker cabinets and custom rigs for working musicians, one at a time. Guitar heads include the Clean Channel (15 or 30 watts, EL84), Atlas (an American clean pedal platform), Bayonet (British-style clean), Hatchet (two channels with boost) and the three-channel Foundry; bass amps include the tube Compass and the solid-state Telegraph, both with parallel clean and drive channels and balanced XLR outputs. Options include spring reverb, tube-driven effects loops, power attenuation and combo builds, and products carry a lifetime transferable warranty (tubes excluded).
Amps use 12AX7 or 6N2 preamp tubes and JJ EL84, EL34, KT88 or KT120 power tubes, with Hammond Classic and 1600 series output transformers on every model. Guitar cabinets are ported, tuned and braced and loaded with Eminence speakers, and the exposed-wood cabinets are finished with natural wood dyes.
Made in: St. Louis, MO (amps and cabinets designed and built by Justin Mills in his shop).
Imported: output transformers come from Hammond, a Canadian maker, and JJ power tubes are made in Slovakia.
Source: Mills Custom, 2026 · Riverfront Times, checked 10/2026
St. Louis, MO
Amplifier makers by state
- California: ATI Amplifier Technologies (Los Angeles area), home theater, stereo and multizone power amplifiers
- Missouri: Mills Custom Amps (St. Louis), tube guitar and bass amplifiers and speaker cabinets
Choosing a power amplifier
- Power ratings: look for watts per channel with all channels driven, across 20 Hz to 20 kHz, at a stated distortion level. Many receivers are rated with only one or two channels driven and deliver far less when all channels play at once.
- Power supply: large toroidal transformers and separate supplies for each channel keep one loud channel from starving the others.
- Class AB or Class D: Class AB amps run warmer and heavier; Class D amps are smaller, cooler and more efficient. Both can sound excellent when well designed.
- Connections: balanced XLR inputs reject noise on long cable runs, and jacks mounted to the chassis hold up better than jacks mounted only to the circuit board.
Choosing a tube guitar or bass amp
- Power tubes: EL84 tubes give a chimey, British-style breakup at low power; EL34, 6L6, KT88 and KT120 tubes give more headroom and low end.
- Wattage: 15 to 30 watts is plenty for home and small clubs; 50 to 100 watts or more keeps a clean tone at band volume. A power attenuator or triode switch lets a big amp break up at lower volume.
- Pedal platform: players who use many pedals often want a clean, high-headroom amp with a tube-driven effects loop.
- Bass: tube bass amps add warmth; solid-state and Class D bass amps add power and less weight. A balanced XLR direct out sends the bass straight to a recording or PA system.
Reading "Made in USA" on amplifiers
Under Federal Trade Commission rules, a plain "Made in USA" claim means all or virtually all of the product is made here. Most amplifiers built in the US use some imported parts, such as tubes, transformers, output modules or semiconductors. The listings on this page say what work happens in the US and name imported parts when a source states them.
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A company may be based in the USA while making some products elsewhere. Check the manufacturer's own site for where a specific product is made.