Helix Competition A4

4-channel car amplifier — 85 watts RMS x 4 (Black)

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  • Helix Competition A4


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Our take on the Helix Competition A4

by Buck Pomerantz

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

An amp that means business

Helix created the Competition A4 amplifier for those of you who want an amp that delivers pure power with uncompromised sonic fidelity. This 4-channel workhorse can drive four 4-ohm speakers with 85 watts RMS each — but that's not all it can do. You can bridge the amp to pump up to 395 watts RMS per channel to a pair of subs.

Meant for display

An A4 amp isn't your typical modest amplifier, hiding under a seat or in a trim pocket, struggling to play music over road noise. The large chassis features a transparent cover that shows off the amp's internal technology and neat design. The A4 doesn't just power your sound system, it makes it stand up and shout. And you can choose an A4 amp in black or silver to match your system's decor.

Read more

Extraordinary features

Gold-plated connections won't tarnish or suffer any oxide buildup that could interfere with the signal flowing in or out of this amplifier. You can set the frequency filters for high-pass or low-pass/bandpass operation, ensuring that you can tune your speaker or subwoofer system to sound its best. There's even a parametric-type bass boost, which allows you to dial in the exact bass notes you want to bump up.


  • 4-channel car amplifier with black trim
  • 85 watts RMS x 4 at 4 ohms (150 watts x 4 at 2 ohms)
  • 395 watts RMS x 2 at 2 ohms
  • Class A input stages, Class AB output
  • 24-karat gold-plated RCA input, power, and speaker connections
  • double-sided copper plated circuit boards
  • noise-free inputs (preamp)
  • variable low-pass/bandpass filters (15-7000 Hz)
  • variable high-pass filter (15-7000 Hz)
  • tunable bass boost (0-9 dB from 30 to 120 Hz )
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • fuse rating: 25A x 3
  • 17"W x 1-7/16"H x 9-1/2"D
  • warranty: 2 years
  • Our 60-day money-back guarantee

Hands-on research from the Crutchfield Labs (what are the Labs?)

Features and Specs
RMS Power Output (Watts x Channels) 85 x 4
Peak Power Output (Watts x Channels) 150 x 4
Power at 2 Ohms (Watts x Channels) 150 x 4
Bridged Power (Watts x Channels) 395 x 2
Minimum Impedance Bridged 2
Minimum Impedance Unbridged 2
Best Frequency Response 15-20000 Hz
THD at Rated RMS Power 0.009%
Signal to Noise Ratio 100 dB
Input Voltage 13.8v
Amplifier Class A
Low-Pass Crossover Frequency 15-7000 Hz
Low-Pass Slope (dB/octave) N/A
High-Pass Crossover Frequency 15-7000 Hz
High-Pass Slope (dB/octave) N/A
Bass Boost 0-9 dB
Bass Boost Frequency 30-120 Hz
Fan Cooled No
Fuse Rating 75
Speaker Level Inputs No
Preamp Outputs No
Width (inches) 17
Height (inches) 1-7/16
Depth (inches) 9-1/2
Parts Warranty 2 Years
Labor Warranty 2 Years
Product Research
What's in the box?

Download owner's manual

  • Four-channel amplifier (black)
  • Three 25A ATM Mini fuses (installed)
  • 4 Self-tapping screws (1.25" length)
  • 4mm Allen wrench
  • 1.5mm Allen wrench
  • Instruction Manual

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.



Helix Amplifiers: Helix amplifiers, made in Germany by Audiotec Fischer, feature high quality components and construction to deliver a superb audio experience. The A4 raises the bar in sound quality and performance to bring you a competition-grade amplifier.

Four-channel Amplifier: The Helix A4 is a Class A 4-channel amplifier built with high grade components with 1% tolerances for the absolute best sound quality. The amp features an extremely stable output stage with select MOSFET transistors, a regulated power supply, 24 carat gold-plated set screw power terminals, and a temperature-optimized aluminum heatsink for efficient heat dissipation.

Configuration Options: The A4 can be operated in 4-channel, 3-channel, or 2-channel modes. To operate in 3-channel mode, Channels C and D must be bridged, because Channels A and B can only be bridged in 2-channel mode. In 2-channel mode, Channels A and B are bridged and Channels C and D are bridged.

Power Output: The amplifier delivers a solid 85 watts RMS per channel at 4 ohms and 150 watts x 4 at 2 ohms. When the amp is bridged, it can deliver 270 watts RMS x 2 at 4 ohms, or 395 watts x 2 at 2 ohms bridged.

Color Protection System: The A4 has a top panel made of translucent Plexiglas which allows you to view the internal components and the amp's LED indicators. Three colored LEDs on the circuit board show the operation mode of the amplifier:

  • Green: The green LED glows to indicate the amplifier is in good operating condition.
  • Yellow: The yellow LED glows to indicate a malfunction of the amplifier, over- or under-voltage, or a short circuit at the loudspeaker output.
  • Red: The red LED glows to indicate the amplifier has shut down due to overheating.


Input Level: The Helix A4 amplifier features four RCA input connectors, each with a rotary input level control. The potentiometers are mounted on the circuit board, and require a small screwdriver (not included) to adjust the input levels through the Plexiglas top panel. The input sensitivity range is 500mV to 8 volts.

Built-in Crossovers: The A4 has built-in crossovers that can be set to High-Pass, Full-Range, or Low-Pass. One crossover affects Channels A and B, and the other is for Channels C and D. The Mode and Frequency Range Switches are located on the circuit board and require a screwdriver to make the adjustments through the Plexiglas top panel. You can set the crossover frequency range to 15-90Hz, 90-800Hz, or 600-7000Hz via the 3-way switches. The cutoff frequency is adjusted within the selected range via the rotary controls on the right side of the amplifier (Frequency Adjust A/B and Frequency Adjust C/D).

Bass Boost: The bass boost is continuously variable from 0 dB to +9 dB. You can also adjust the center frequency of the bass boost between 30Hz and 120Hz. Both controls are located on the right side of the amplifier.

Input Signal Switch (for Channels C & D): If you only have a mono input signal in bridged mode on Channels C and D, you can drive both channels without using a Y-adapter by switching the Input Signal Switch to the #2 position. If there are separate input signals for Channels C and D, the switch should remain in the #1 position.

Full Active Operating Mode: When the A4 is set to Full Active Operating Mode (via a switch on the right side of the amp), the signals from inputs A and B are full range, or high-passed based on the selected cutoff frequency on Channels A and B, and low-passed on Channels C and D. When operating in Full Active Mode, you can adjust the output of Channels C and D, relative to Channels A and B via two top-mounted potentiometers. The range of adjustment is from -6dB to +6dB.


Power: The A4 is equipped with 24 carat gold-plated set-screw terminals for power and ground. These terminals will accept up to 4-gauge wire, and are tightened/loosened with the supplied 4mm Allen wrench.

Fuse: The amp is protected by three 25-amp ATM mini fuses, installed under the Plexiglas top panel. It is recommended that a 75-amp fuse be installed on the power wire, 12" or less from the battery. If you use a pre-packaged amp wiring kit with a fuse that has a different value than 75 amps, you should replace the fuse with a 75-amp fuse.

Remote: The amp's remote turn-on features a set-screw terminal that will accept up to 12-gauge wire, and is tightened/loosened with the supplied 1.5mm Allen wrench.

Speaker Outputs: The amp has four pairs of 24 carat gold-plated screw terminal speaker outputs which accept spade lugs up to 0.3" wide. To bridge the amplifier, the speaker wires should be connected to the B+ and A- terminals and the D+ and C- terminals, as indicated on the amplifier.

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