Alpine MRV-M250 Car Amplifier

The Alpine MRV-M250 is a Class D, single-channel car amplifier designed for a subwoofer. It suits a car audio system that needs separate amplification for bass. Its rated output is 150 W RMS into 4 Ω or 250 W RMS into 2 Ω. Both ratings are measured at a 14.4 V supply voltage with less than 1% THD+N, so keep those conditions in mind when comparing power figures.

Construction and installation

The amplifier uses a MOSFET DC-DC PWM power supply, a separate preamplifier stage and a MOSFET output stage. Its screw terminals are arranged on two sides of the housing. When choosing a mounting position, allow room at both edges to route and secure the cables.

The complete housing is 190 mm wide, while the heatsink is 155 mm wide. Use the complete housing dimensions when checking the available space, and leave the heatsink clear so it can dissipate heat. The amplifier weighs 1.5 kg. An LED power indicator shows whether the unit is on.

Connecting the signal

You can feed the MRV-M250 through its RCA input or its speaker-level inputs. Choose RCA when the car audio source has a suitable line output. The speaker-level inputs take their signal from the source’s speaker outputs. Each connection method has its own input-sensitivity range, so set the gain with the chosen source in mind.

There are four channels of speaker-level input, but only one amplified output channel. The input count does not make this a four-channel amplifier for the car’s main speakers. When a speaker-level signal is connected, the amplifier can turn on automatically when an input signal appears.

Setting up the bass

The adjustable low-pass filter limits the higher frequencies sent to the subwoofer. Its cutoff can be set from 50 to 400 Hz, with a 24 dB-per-octave slope. Start with a setting that works alongside the rest of the car’s speakers, then listen and adjust it. The aim is to set how the subwoofer joins the other speakers, rather than choosing a cutoff from the amplifier’s range alone.

The gain control is continuously adjustable. Match it to the selected input signal, starting at a lower setting. The built-in bass equalizer can add up to 12 dB at 50 Hz. Listen to the system with your chosen filter setting before adjusting the equalizer, since the filter and equalizer affect different parts of the bass setup.

To change the level from the driver’s seat, you need the RUX-KNOB remote control, which is sold separately. It can reduce the level by up to 20 dB from the level set on the amplifier. This is useful if you expect to change the subwoofer level while using the system; the filter, equalizer and gain can still be set on the amplifier itself.

Power, load and protection

When choosing a subwoofer, consider the final load it presents to the amplifier. The stated rated-power figures apply at 4 Ω and 2 Ω. No operating figure is given for a load below 2 Ω. The 550 W total maximum power figure is separate from the rated RMS output and should not be read as an RMS rating.

The 14.4 V figure is the supply voltage used for the power measurements; the specified operating supply range is 11-16 V DC. Protection circuits cover current limiting, overvoltage, undervoltage and heat. The multistage thermal protection can limit output power as the unit heats up. The amplifier also uses an S.T.A.R. circuit.

Technical specifications

Type and purpose	Class D, single-channel car subwoofer amplifier
Amplified channels	1
Rated power at 4 Ω	150 W RMS × 1; 14.4 V, THD+N <1%
Rated power at 2 Ω	250 W RMS × 1; 14.4 V, THD+N <1%
Total maximum power	550 W
Power supply	MOSFET DC-DC PWM
Amplification stages	Separate preamplifier stage; MOSFET output stage
Supply voltage	14.4 V DC; operating range 11-16 V DC
RCA input	Input sensitivity 0.15-4.0 V
Speaker-level inputs	4 channels; input sensitivity 0.4-10 V
Input impedance	>10 kΩ
Automatic turn-on	When a speaker-level input signal is present
Low-pass filter	Adjustable, 50-400 Hz; 24 dB/octave
Gain adjustment	Continuous
Bass equalizer	0-12 dB; 50 Hz center frequency
Remote level adjustment	0 to -20 dB; requires the separately sold RUX-KNOB
Frequency response	7-400 Hz (+0/-3 dB; 1 W into 4 Ω)
THD+N at 4 Ω	<0.02% at 10 W
THD+N at 2 Ω	<0.03% at 10 W
Damping factor	>500; 10 W into 4 Ω at 100 Hz
Signal-to-noise ratio	>85 dB at 1 W into 4 Ω; >105 dB at rated power into 4 Ω
Protection	Current limiting, overvoltage, undervoltage and multistage thermal protection that can limit output power
Other circuit	S.T.A.R. circuit
Indicator	LED power indicator
Terminals	Screw terminals on two sides
Overall dimensions	190 × 55 × 200 mm
Heatsink dimensions	155 × 55 × 200 mm
Weight	1.5 kg

FAQ

Does this amplifier replace a four-channel car amplifier?

No. The four channels refer to the speaker-level inputs. The amplifier has one amplified subwoofer output channel, so the main speakers need separate amplification.

When should I use RCA or the speaker-level input?

Use RCA with a line output from the audio source. Choose the speaker-level input when taking a signal from the source’s speaker outputs. Set the gain for the input you use.