Helix Amplify 204 X-Over 4 Channel Amplifier with Crossover and DSP Input

The Helix Amplify 204 X-Over (AC20420) is a compact 4-channel Class D car amplifier with a built-in active crossover and DirectDSP mode, part of the Helix Amplify 2-Series range.

If you already use a separate DSP, the Helix Amplify 206 DSP 6-channel model may be worth considering instead.

Key specifications

• Channels: 4, fully bridgeable
• Power: 4 x 100 W RMS @ 4 Ω, 4 x 190 W RMS @ 2 Ω, 2 x 380 W RMS bridged @ 4 Ω
• Integrated active crossover with adjustable high- and low-pass filters plus input mode switch
• DirectDSP function to bypass the crossover for use with an external DSP
• Switchable high-level and RCA inputs, up to 16 V input sensitivity, with ADEP.3 for OEM radios
• Automatic turn-on and start-stop capability down to 6 V
• Advanced Class D design for high efficiency and low heat dissipation
• Very compact dimensions for space-saving installation

The Amplify series takes a specialised approach to amplifier design — each model is built for a specific application rather than trying to do everything. The 2-Series forms the technical core of the platform, combining powerful Class D performance, fully bridgeable multi-channel outputs, and excellent efficiency with straightforward real-world integration.

• Up to 240 W RMS @ 2 Ω per channel for strong dynamics and powerful sound
• Fully bridgeable output channels for flexible system configurations
• Very compact design for space-saving installation
• Start-stop capability down to 6 V supply voltage
• Integrated active crossover with adjustable high- and low-pass filters and input mode switch
• DirectDSP function — input signal bypasses the active crossover and is routed unfiltered to the output stage
• Smart high-level input with ADEP.3 for clean integration into OEM sound systems
• Advanced Class D design for high efficiency and low heat dissipation

The 2-Series suits a wide range of setups — from flexible 6-channel full-range configurations to dedicated mono subwoofer solutions. Whether as a DIRECT, X-OVER, or DSP variant, there is a tailored option for each configuration.

AMPLIFY 204 – The versatile solution for full-range applications

The AMPLIFY 204 combines four fully bridgeable outputs with strong sound quality and performance, making it well suited to front-end or multi-channel setups. It runs as a classic 4-channel system, a 3-channel configuration with subwoofer, or a bridged 2-channel layout — adapting to a wide range of vehicles and system requirements. Output is 4 x 100 W RMS @ 4 Ω, 4 x 190 W RMS @ 2 Ω, or 2 x 380 W RMS bridged @ 4 Ω.

Sound and power – above the standard

All amplifiers in the Amplify 2-Series offer strong sound performance, minimal distortion, and a high signal-to-noise ratio, combined with fully bridgeable multi-channel outputs for maximum power and installation flexibility.

AMPLIFY X-OVER – Maximum flexibility for classic upgrades

The X-OVER models are designed for conventional sound upgrades using factory or aftermarket head units. The integrated active crossover features adjustable high- and low-pass filters and an input mode switch for precise signal tuning across a variety of system layouts — active front with separate tweeter and woofer channels, passive front and rear speakers, or a combined front and subwoofer setup via bridged channels.

Switchable high-level and RCA inputs with up to 16 V input sensitivity allow integration into nearly any OEM or aftermarket environment. The ADEP.3 circuit ensures reliable communication with factory radios, and the automatic turn-on function simplifies installation. The DirectDSP function allows the input signal to bypass the internal crossover entirely, routing it unfiltered to the output stage — ideal for users planning to add an external DSP later.

Form follows performance

The Amplify 2-Series has a compact form factor that allows flexible installation even in tight spaces. A removable top cover conceals all connections and controls, offering protection and a clean finish. Matte surfaces, sharp contours, and a minimalist design integrate neatly into any modern vehicle interior.