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Helix Amplify 204 Direct 4-Channel Fully Bridgeable Class D Amplifier with DirectDSP Inputs
A 4-channel fully bridgeable Class D amplifier from the Helix Amplify 2-Series, the Amplify 204 Direct delivers 4 x 100W RMS at 4Ω, 4 x 190W RMS at 2Ω, and 2 x 380W RMS bridged at 4Ω (up to 240W per channel maximum at 2Ω), with 4 DirectDSP RCA inputs (1-8V), clipping LED for gain calibration, 99dB SNR at full power, THD below 0.012% at 1kHz, stereo/mono switch for bridged single-RCA operation, Start-Stop capability, and a removable top cover in an ultra-compact 40 x 248 x 114mm housing.
Product Overview
The Helix Amplify 204 Direct is the DSP-optimised variant of the Amplify 204 4-channel amplifier, designed exclusively as a clean, transparent amplification stage in DSP-based audio systems. As the DIRECT variant, it features DirectDSP inputs that eliminate conventional input filtering stages entirely, preserving uncompromised signal integrity from the connected DSP processor output through to the speaker outputs. This focus on essential core components and minimal input architecture keeps noise and distortion at their absolute minimum.
The fully bridgeable 4-channel architecture delivers identical output power to the 204 X-Over: 4 x 100W RMS at 4Ω, 4 x 190W RMS at 2Ω, and 2 x 380W RMS bridged at 4Ω, with maximum output of up to 240W per channel at 2Ω. SNR is 99dB at full power, THD at 1kHz into 4Ω is below 0.012%, and THD+N below 0.02%, matching the X-Over variant in audio performance.
The 4 DirectDSP RCA inputs accept 1-8V from DSP processor outputs with a high input impedance of 67kΩ, minimising loading on the upstream DSP stage. A practical stereo/mono switch for each stereo input pair allows bridged operation from a single RCA signal, eliminating the need for external Y-adaptors when only one output channel is available from the DSP. A clipping LED provides real-time visual feedback for precise and fast gain calibration. The removable top cover conceals all connections and controls when installed. Operating voltage is 10.5-16V with Start-Stop capability to 6V. Fused at 2 x 30A LP-Mini (APS).
Features & Benefits
4 x 100W RMS at 4Ω / 2 x 380W RMS Bridged - Flexible Multi-Configuration Output: Delivers 4 x 100W RMS at 4Ω, 4 x 190W RMS at 2Ω, or 2 x 380W RMS bridged at 4Ω, providing maximum configuration flexibility for front channel, full-range, and bridged subwoofer applications in DSP-based multi-amplifier systems.
DirectDSP Inputs - Designed for External DSP Processors: The DirectDSP input design eliminates conventional input filtering stages to ensure uncompromised signal integrity and maximum clarity from the DSP processor output. The minimal input architecture keeps noise and distortion at their absolute minimum, delivering the cleanest possible amplification of the processed DSP signal.
Stereo/Mono Switch - Bridged Operation from Single RCA Input: A stereo/mono switch for each stereo input pair allows bridged mono operation from a single RCA channel, eliminating the need for an external Y-adaptor when only one output channel is available from the upstream DSP processor or head unit.
99dB SNR at Full Power - THD Below 0.012% at 1kHz: Delivers 99dB SNR (A-weighted) at full power and THD below 0.012% at 1kHz into 4Ω for audio performance that exceeds conventional 4-channel amplifier standards.
67kΩ Input Impedance - Minimal Loading on DSP Outputs: The very high 67kΩ input impedance presents minimal loading on the upstream DSP processor's output stage, preserving the DSP output's signal integrity and preventing impedance-related signal level changes.
Fully Bridgeable Multi-Channel Architecture: All 4 output channels are fully bridgeable in any combination for classic 4-channel, 3-channel, and 2-channel bridged configurations to suit a wide range of vehicles and system requirements.
Clipping LED for Fast and Precise Gain Adjustment: The clipping LED provides real-time visual indication of amplifier clipping during gain calibration, enabling precise and fast level setting without requiring external measurement equipment.
No Input Filtering - Uncompromised Signal Path: The DIRECT variant has no highpass, lowpass, or any other filter controls. All signal processing and crossover functions are handled entirely by the upstream DSP processor, preventing double-filtering artefacts and preserving complete signal integrity in DSP-based systems.
Advanced Class D - High Efficiency and Low Heat Dissipation: The advanced Class D concept delivers high efficiency and very low heat dissipation, enabling 4 x 190W RMS at 2Ω from an ultra-compact 40 x 248 x 114mm housing.
Removable Top Cover - Clean Appearance and Connection Protection: The removable top cover conceals all connections and controls when installed, providing a clean streamlined appearance and additional protection for wiring and gain adjustments.
Start-Stop Capable - 10.5-16V Operating Range: Start-Stop capable power supply maintains stable operation during voltage drops to 6V for up to 5 seconds.
What's in the Box
- Helix Amplify 204 Direct Amplifier
- 2 x Allen Key
- 1 x Mounting Material
- 1 x Connection Cable
- 2 x Fuse
- Instruction Manual
Technical Specs
| Specification | Detail |
|---|---|
| SKU | AMPLIFY 204 DIRECT |
| Brand | Helix |
| Range | Amplify 2-Series |
| Variant | Direct (DirectDSP Inputs) |
| Channels | 4 (Fully Bridgeable) |
| Amplifier Class | Class D |
| Built-in DSP | No |
| Power RMS - 4Ch at 4Ω (14.4V) | 4 x 100W |
| Power RMS - 4Ch at 2Ω (14.4V) | 4 x 190W |
| Power RMS - Bridged 2Ch at 4Ω | 2 x 380W |
| Max Output per Channel at 2Ω | Up to 240W RMS |
| THD at 1kHz, 1W into 4Ω | Less than 0.012% |
| THD+N at 1kHz, 1W into 4Ω | Less than 0.02% |
| SNR at Full Power | 99dB (A-weighted) |
| Damping Factor | 70 |
| RCA Inputs | 4 x RCA DirectDSP (1-8V, 67kΩ) |
| High-Level Inputs | None |
| Input Type | DirectDSP |
| Outputs | 4 x Speaker |
| RCA Preout | None |
| Frequency Response | 10Hz-20,000Hz |
| Highpass Filter | None (DIRECT variant) |
| Lowpass Filter | None (DIRECT variant) |
| Stereo/Mono Switch | Yes (per stereo input pair) |
| Clipping LED | Yes |
| ADEP.3 | None (DIRECT variant) |
| Auto Turn-On | None (DIRECT variant) |
| Operating Voltage | 10.5-16V (Stable to 6V for 5 Seconds) |
| Power Rating | DC 12V, 70A Max |
| Idle Current | 1100mA |
| Fuse | 2 x 30A LP-Mini (APS) |
| Operating Temperature | -40°C to +70°C |
| Start-Stop Capable | Yes |
| Top Cover | Removable |
| Dimensions | 40mm x 248mm x 114mm |
Compatible With
The Amplify 204 Direct is compatible with 10.5-16V vehicle electrical systems. RCA inputs accept 1-8V from DSP processor outputs. The Amplify 204 Direct has no high-level inputs, no RCA preout, and no onboard filtering. All crossover and signal processing must be handled by the upstream DSP processor. Confirm channel bridging configuration and minimum speaker impedance (4Ω for bridged) before purchase. Designed for use with Helix and Match DSP amplifiers and processors including the V Eight DSP Ultimate, P Six DSP Ultimate, Match UP 8DSP, Match UP 6DSP, and other compatible DSP sources.
Frequently Asked Questions
What is the difference between the Amplify 204 Direct and the Amplify 204 X-Over?
Both are identical in output power, dimensions, and amplifier class. The Amplify 204 Direct features DirectDSP RCA inputs with no onboard filtering, designed as a clean amplification stage downstream of a DSP processor. It has no high-level inputs, no ADEP.3, no auto turn-on, and no crossover controls. The Amplify 204 X-Over includes 4 high-level ADEP.3 inputs (up to 16V), an integrated active crossover with adjustable highpass and lowpass filters, auto turn-on, and a DirectDSP bypass function. Choose the Direct for DSP-based systems; choose the X-Over for standalone installations with factory or aftermarket head units.
Does the Amplify 204 Direct have any onboard filters?
No. The Amplify 204 Direct has no highpass, lowpass, subsonic, or any other filter controls. All signal processing and crossover functions must be handled entirely by the upstream DSP processor.
What is the stereo/mono switch on the Amplify 204 Direct?
A stereo/mono switch for each stereo input pair allows bridged mono operation from a single RCA input, eliminating the need for an external Y-adaptor when only one output channel is available from the upstream DSP processor.
Does the Amplify 204 Direct have high-level inputs?
No. The Amplify 204 Direct accepts RCA input only (4 x DirectDSP RCA at 1-8V). It has no high-level inputs and no auto turn-on function. A remote wire or DSP remote output is required for amplifier activation.
What DSP processors is the Amplify 204 Direct compatible with?
The Amplify 204 Direct is optimised for use with Helix and Match DSP amplifiers and processors including the Helix V Eight DSP Ultimate, Helix P Six DSP Ultimate, Match UP 8DSP, Match UP 6DSP, Match M 5.4DSP, and other compatible DSP sources with RCA outputs in the 1-8V range.
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