Monural Subwoofer Amplifier

The Stealth Acoustics SA255 MKII is an integrated monaural subwoofer amplifier/crossover system designed as a low distortion power source for Stealth Acoustics invisible subwoofer panels or other un-powered subwoofers.  The SA255 MKII can also be used for full range speakers when the low pass filter is off.  Intended for whole house audio or home theater bass applications, the SA255 MKII may stack with other components or mount in a standard 19” equipment rack requiring two RU spaces (3-1/2”) with the provided removable rack mount ears. The SA255 MKII delivers a solid 250 watts into an 8Ω load and 350 watts into 4Ω.  A variable low pass, 18db per octave filter allows for infinite crossover points from 50Hz to 150Hz.

With a full complement of input and output connectors, the SA255 MKII is easily integrated into any audio system. Inputs include RCA line level, balanced XLR line level, and phoenix connector speaker level, all with pass-through capability. The speaker level input/pass-through connections allow the SA255 MKII to feed directly from full-range speaker lines, anywhere in the system. The SA255 MKII’s amplifier output connection is via a 5-way binding post designed to accept heavy gauge speaker wires. A selectable automatic turn-on feature activates the amplifier only when audio signals are present. Other features include an internal, quiet, 8-stage cooling fan that automatically engages as required.

Front panel controls include volume control, variable low pass filter, phase control, power switch and six power output monitor LED’s. Rear power controls consist of filter bypass switch for full range operation, no signal mute switch and 3-position panel graphics control switch. 115VAC and 230VAC input line voltages are selectable, via a rear panel switch.

The Stealth Acoustics SA255 MKII subwoofer amplifier is covered by a 2-Year manufacturer’s warranty.


Mono Power Output

250 watts @ 8 < 0.05 THD
350 watts @ 4 < 0.05 THD

Total Harmonic Distortion

<0.05 @ 1 watt 4 / 100Hz

Signal to Noise Ratio

86 dB below rated output

Crossover Section

Low Pass Filter: 50Hz – 150Hz / 18 dB per octave (variable with bypass switch)
High Pass Filter: 18Hz / 30 dB per octave (fixed)

System Impedance

8Ω nominal – 4Ω minimum

Current Draw

6.2A @ 350W/4 – 115VAC/60Hz


Width: 19” (482 mm)
Height: 3-1/2” (89 mm) – without feet
Depth: 13-5/8” (346 mm)


Black anodized aluminum


Product Weight: 31.3 Lbs. (14.20 kg)
Shipping Weight: 32.5 Lbs. (14.74 kg)

Included Accessories

Removable power cord
Removable rack ears

Features & Functions

Rack Mountable

(2) RU spaces: 3-1/2” (89 mm)

DC Protected

Fixed high pass filter @ 18Hz

Variable Low Pass Filter

50 to 150Hz / 18 dB per octave

Power Standby LED

Red = Standby| Blue = Active

Auto On/Standby Function

Switch selectable on/off

Flexible Inputs with Pass Through

Binding post speaker level inputs / outputs
RCA line level inputs / outputs
XLR balanced line inputs / outputs

Amplifier Output Connector

5-way binding post

Output monitor LED’s

6 level readings

Phase Switch

Low Pass Filter On/Off Switch

Fan Cooled

Automatic – 8 speed stages

110v and 220v Input Voltages


Specification Sheet
User Guide
Pro-Power Amplifier Flyer
Pro-Power Amplifier Brochure