Fosi Audio ZA3 Balanced Dual-Mode Class-D Amplifier Stereo Mono Switchable

Fosi Audio ZA3 Balanced Dual-Mode Class-D Amplifier — Stereo + Mono Switchable

Fosi Audio ZA3 is a compact TPA3255 Class-D power amplifier with an XLR/TRS combo input, RCA inputs, a filtered subwoofer output, a 12 V trigger and a front-panel stereo/mono switch. One unit drives a pair of passive speakers in stereo mode; in mono mode one unit drives one speaker, so two units can run as a monoblock pair. It is a power amp only: no DAC, preamp or Bluetooth. Fosi’s store lists it from $109.99 without a power supply, $129.99 with a 32 V/5 A supply and $149.99 with a 48 V/5 A supply (checked 2026-10-31). Read our ZA3 review roundup for the independent measurements. Direct from Fosi, or Amazon US.

$109.99

Get Deal on AmazonGet Deal on eBay

Video Review

Fosi Audio ZA3: balanced-input Class-D amp with switchable stereo or mono

The ZA3 is Fosi’s flexible small power amp. It uses the Texas Instruments TPA3255 chip and has an XLR/TRS combo input plus RCA, a filtered subwoofer output and a 12 V trigger. A switch on the front panel selects stereo or mono (bridged) operation. Run one unit in stereo for a pair of speakers now, and add a second one later if you want a monoblock pair. Our ZA3 review roundup compares what Audio Science Review, Erin’s Audio Corner and other reviewers found, and lists what we could not verify.

What it offers

  • Stereo / mono switch on the front panel. In mono mode one ZA3 drives one speaker. Fosi’s spec list gives 180 W x 2 in stereo and 235 W in mono at 4 ohm; the same page also says “up to 155 W”, so treat the ratings as optimistic.
  • XLR/TRS combo and RCA inputs, plus a 12 V trigger input.
  • Filtered subwoofer output. Fosi gives no cutoff frequency, and reviewers quote anything from 120 to 300 Hz.
  • Swappable op-amps (Fosi lists op-amp rolling) and a small case: 6.1 x 7.2 x 2.0 in (15.49 x 18.39 x 5.08 cm), 3.9 lb (1.78 kg).
  • DC input range 24 to 48 V. Fosi sells it without a supply, or with a 32 V/5 A or 48 V/5 A supply. Warranty: 24 months.

Who it’s for

Anyone who wants a small TPA3255 amp for passive speakers, with a balanced input or a subwoofer output, and room to add a second unit later. Compare it with the AIYIMA A20 MONO (monoblock, PFFB) and the Fosi BT20A MAX (Bluetooth, remote).

Who should skip it

Skip the ZA3 if you need a built-in DAC, preamp, Bluetooth or a headphone output; it has none of them. If you do not need balanced input, a sub output or mono mode, the smaller Fosi V3 Mini has RCA inputs only. Independent measurements also show frequency response that shifts with speaker impedance, so easy 6 to 8 ohm speakers are the safest match.

Common questions

How much power does it make? Fosi’s page shows 155 W, 180 W and 2 x 300 W for the same amp. Erin’s Audio Corner measured 4-ohm power below the rating with both channels driven. See the review roundup for the sources.

Can I use a larger power supply, such as a 48 V 10 A unit? Fosi states a 24 to 48 V DC input range and sells 32 V/5 A and 48 V/5 A supplies. We found no Fosi statement about larger third-party supplies, so ask Fosi before buying one.

How does it compare with the Fosi V3? The ZA3 adds the XLR/TRS combo input, the sub output, the 12 V trigger and the mono switch. Fosi lists slightly better THD and SNR figures for the V3 Mini, and TNT-Audio heard the V3 as a little richer in the treble on a revealing system.

Where to buy

From Fosi’s store or Amazon US. Both buttons are below.

SKU: fosi-audio-za3 Category: Brand:
Summary of public owner feedback and independent reviews as of 2026-10-31. It is not our own testing. Sources and details are in our ZA3 review roundup.

What owners and reviewers praise

  • One box that can grow. Start in stereo, add a second unit later and set both to mono.
  • Balanced XLR/TRS and RCA inputs and a filtered subwoofer output in a small, inexpensive amp.
  • Cool running. Audio Science Review and Pragmatic Audio both found it stayed cool.
  • Measured above average. Audio Science Review placed it above the average of the amplifiers it has tested and recommended it (Feb 2024).

Critical notes

  • No DAC, preamp or Bluetooth. You need a source with its own volume control, or a preamp.
  • Power ratings are inconsistent (155 W, 180 W, 2 x 300 W on Fosi's page). Erin's Audio Corner measured 4-ohm power below the rating with both channels driven (Mar 2024).
  • No PFFB (Ear-Fidelity), and frequency response shifts with speaker impedance (ASR, Erin's Audio Corner).
  • Small binding posts, no remote, and the power switch is the volume knob.
  • Mono mode lowers SINAD by about 13 dB in ASR's measurements, and some owners find the benefit subtle.
  • Subwoofer filter cutoff is not stated by Fosi, and reviewers disagree (120 to 300 Hz).

Setup notes

  • Easy 6 to 8 ohm speakers leave the most margin.
  • With two units as monoblocks, set both volume knobs to maximum and control the level from a DAC or preamp.
  • Switch the amp off before changing modes (our precaution; Fosi gives no guidance).

Related

🔥 See Today's Deal on Amazon

Specification

BrandFosi Audio
ModelZA3
TypeStereo / mono switchable Class-D power amplifier
Amplifier ChipsetTexas Instruments TPA3255
Stereo Output180 W x 2 at 4 ohm (Fosi spec list; the same page also says up to 155 W)
Mono Bridged Output235 W at 4 ohm (Fosi spec list; the same page also says 2 x 300 W)
Mode SwitchFront-panel stereo / mono toggle
Speaker Impedance2 - 8 ohm (Fosi rating)
InputsXLR / 1/4-inch TRS combo jack, RCA, 12 V trigger
Subwoofer OutputFiltered subwoofer output (cutoff not stated by Fosi)
THD / SINAD / SNRUnder 0.006% / 89 dB / 106 dB or better (Fosi)
Dimensions6.1 x 7.2 x 2.0 in (15.49 x 18.39 x 5.08 cm)
Weight3.9 lb (1.78 kg)
DC Input24 - 48 V; sold with a 32 V/5 A or 48 V/5 A supply, or without one
Warranty24 months (Fosi)

Based on 0 reviews

0.0 overall
0
0
0
0
0

Be the first to review “Fosi Audio ZA3 Balanced Dual-Mode Class-D Amplifier — Stereo + Mono Switchable”

There are no reviews yet.

Related buying guides

Advertisement
Advertise with Budget Audiophile - 300x250 ad space

Related products