FOSI AUDIO M04 Mono/Subwoofer Amplifier

The Fosi Audio M04 is a Class D amplifier based on a TPA3116 chip and capable of delivering 100W into 3 ohm. The M04 has an RCA input and a speaker terminal output. It can be used with speakers as a mono amplifier, thanks to its “PBTL” mode, or with a passive subwoofer, thanks to its “SUB” mode. A potentiometer on the front panel adjusts the subwoofer output crossover frequency from 20Hz to 200Hz. It is therefore ideal for users wishing to feed a subwoofer for immersive sound reproduction, or for users wishing to set up a dual-mono HiFi system.

Fosi Audio M04: PBTL/SUB modes

The Fosi Audio M04 features a switch on the front panel to select between PBTL and SUB modes. PBTL mode enables it to power a passive loudspeaker, while SUB mode, as its name suggests, enables it to power a passive subwoofer. The M04 has an overall frequency response of 20Hz-20kHz (±3db), but a potentiometer lets you adjust the subwoofer cutoff frequency from 20Hz to 200Hz.