The Sound Town STPA3L-400D Class-D plate amplifier enables you to build your own powered speaker cabinet. The STPA3L-400D power amp is equipped with two 1/4” line inputs, two 1/4” mic & XLR combo inputs, one 1/8” AUX input and one XLR loop output connector. The built-in Bluetooth allows you to connect with your Bluetooth enabled mobile devices instantly. The onboard two-band EQ per input channel helps tune the sound to your preference. Simply turn the treble or bass knob and adjust the level of high or low frequencies to match your audio signal perfectly.

The plate power amp generates 400W RMS (4-ohm) and comes with overload protection. When paired with the right speaker driver and enclosure, it produces clear and massive sound to reinforce your PA system.

  • 400W RMS (4-ohm) Class-D power amplifier plate
  • 2-channel 1/4" line inputs, 1 XLR and 1/4" mic combo input and 1 1/8” AUX input
  • 1 XLR loop output
  • Bluetooth connectivity
  • 2-band EQ with bass and treble control


Model STPA3L-400D
Description 3-channel input plate amplifier
Type Class-D
Supports Impedance 4Ω & 
Power 400W RMS: 350W for LF + 50W for HF @4ohm
Feature Bluetooth, 3-channel input
Input 2-channel 1/4" (LINE) / 1/4" & XLR combo (MIC) + 1 channel 1/8" (AUX) / Bluetooth
Output XLR (3-channel loop out)
Control Master volume; each channel: treble, bass, gain
Protection Overload and overcurrent protection
Technical specifications Crossover point: 2.5k hz
Voltage 110V-220V switchable
Speaker model# reference KALE-112BPW

Dimension & Weight

Product Width (in.) 6.46" Package Width (in.) 8.66"
Product Height (in.) 16.54" Package Height (in.) 17.91"
Product Depth (in.) 3.54" Package Depth (in.) 6.10"
Product Weight (lb.) 6.7 lbs Package Weight (lb.) 8.36 lbs

Manufacturer Warranty 1 Year


Sound Town STPA3L-400D Class-D 400W RMS Plate Amplifier for Full-range Loudspeaker Cabinets w/ Bluetooth, 3-Channel Mixer - Connection Instructions, How to Install

“If I buy 2 can they be linked for a right and left channel?”
(Answer): They can be linked by L & R channel by line in but not Bluetooth.

“How far from the amp will the Bluetooth connect?”
(Answer): The Bluetooth distance is about 10 meters without obstacles.

“When in the Bluetooth mode can I get the signal out thru the XLR out?”
(Answer): The Bluetooth feature is for a single speaker, not two. However, when in Bluetooth mode, you can get the signal out thru the XLR out to the other (mono out).

“On the STPA3L-400D plate amp does it have a built-in crossover at 2500hz?”
(Answer): This amp. has a 2-channel amp. (bi-amp), one channel powers the HF and the other channel powers the LF; it has crossover 2.5k Hz built-in.