Rebec RPX-B680 Plus – Hybrid 6-Channel DSP Amplifier

Product Overview

The Rebec RPX-B680 Plus is a six-channel DSP amplifier from Rebec’s RPX-B Series, combining four Class AB amplifier channels with two higher-power Class D channels in a compact integrated platform.

This hybrid amplifier architecture is the key characteristic of the RPX-B680 Plus. Channels 1–4 provide amplification for the main speaker channels, while channels 5–6 offer higher output power and can be used for speaker sections requiring additional power, such as midbass drivers.

Alongside its six amplified outputs, the RPX-B680 Plus provides eight low-level outputs, multi-source connectivity and an AP5688-based DSP platform with PC/App tuning.

Hybrid Class AB + Class D Amplifier Architecture

Rather than using the same amplifier topology and output capability across all six channels, the Rebec RPX-B680 Plus divides its amplifier section into two groups.

Channels 1–4 use Class AB amplification, while channels 5–6 use Class D amplification.

At 14.4V and 4Ω, the amplifier provides:

25W RMS × 4CH + 50W RMS × 2CH, measured at 0.1% THD.

At 3Ω, output increases to:

33W RMS × 4CH + 77W RMS × 2CH, also measured at 0.1% THD.

This asymmetric power distribution allows the six amplifier channels to perform different roles within the same audio system rather than providing identical power to every loudspeaker.

Higher-Power Channels for Midbass

The additional output capability of channels 5–6 is an important distinction of the Rebec RPX-B680 Plus.

Rebec specifically identifies these two stronger channels as providing more power for midbass. This allows the higher-output Class D channels to be assigned to the midbass section while the four Class AB channels handle other loudspeaker sections.

For example, in an active three-way front system, four channels can be assigned to the tweeters and midrange drivers, while the two higher-power channels are available for the left and right midbass drivers.

The actual channel assignment remains dependent on the system design, but the 4+2 architecture provides a practical power distribution for configurations where not every speaker section has the same amplification requirement.

8-Channel DSP Output and External Amplifier Expansion

The Rebec RPX-B680 Plus is not limited to its six internal amplifier channels.

It provides eight low-level outputs at 2.35V, allowing processed signals to be sent to external power amplifiers.

This means the internal six-channel amplifier can handle selected loudspeaker sections while the remaining DSP outputs can be used to expand the system.

For example, an external amplifier can be added for a subwoofer or other channels without replacing the DSP amplifier itself.

This combination of six amplified channels and eight processed low-level outputs gives the RPX-B680 Plus flexibility for both integrated and expanded system configurations.

AP5688 DSP Processing

The RPX-B680 Plus uses the AP5688 DSP chipset, together with a CJC4344 DAC and ES7210 ADC.

DSP processing operates at a 48kHz sampling frequency.

For system tuning, the processor provides a 31-band EQ, while its crossover section supports Butterworth, Linkwitz and Bessel filter types.

The system also provides six presets for saving and recalling different tuning configurations.

Adjustment can be performed through PC or App, allowing the audio system to be configured according to the loudspeaker layout and acoustic requirements of the vehicle.

Analog and Digital Source Integration

The Rebec RPX-B680 Plus provides several options for source integration.

It includes four high-level inputs supporting 7.9–24.9Vpp, allowing connection to compatible factory speaker-level signals.

Unlike the B680V2’s two-channel low-level input, the RPX-B680 Plus provides four low-level inputs supporting 1.3–5.1Vpp, giving it additional analog input channels.

Digital audio can be received through Optical (Toslink) and Coaxial inputs, both supporting signals up to 96kHz/24-bit.

The unit also includes USB Audio input and built-in Bluetooth 5.2.

This provides multiple connection options for factory audio systems, aftermarket sources and external digital playback devices.

Signal Performance and Compact Installation

The Rebec RPX-B680 Plus has a specified frequency response of 20Hz–20kHz, a dynamic range of 93dB, and a signal-to-noise ratio of 105dB.

Total harmonic distortion is specified at below 0.01% for low-level signals and below 0.03% for high-level signals.

Despite combining two different amplifier topologies with DSP processing, the unit measures approximately 120 × 167 × 43 mm.

Operating voltage is 10–16V, with a standby current of 440mA and maximum current of 25A.

More Power Where the System Needs It

The main characteristic of the Rebec RPX-B680 Plus is not simply that it has six amplifier channels, but that those channels are deliberately divided into four Class AB channels and two higher-power Class D channels.

With 25W ×4 + 50W ×2 RMS at 4Ω, the two additional Class D channels provide increased power for applications such as midbass, while the eight-channel DSP output allows the system to expand through external amplification when required.

Combined with the AP5688 DSP, 31-band EQ, multiple crossover types, six presets, PC/App tuning, 96kHz/24-bit Optical and Coaxial inputs, USB Audio and Bluetooth 5.2, the RPX-B680 Plus provides a flexible DSP amplifier platform for multi-channel car audio systems.

Rebec RPX-B680 Plus

Hybrid Class AB + Class D DSP amplification with two higher-power channels for flexible multi-way car audio system design.