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A tube amplifier for your car

The Esprit Series E400 amplifier from Helix uses two triode vacuum tubes in its preamp stage to give your music the pleasing sound that only tubes can create, but with the reliability of a solid-state output section. This 4-channel amp delivers 110 watts RMS to each of your front and rear speakers, giving you the clean headroom you need to get truly dynamic performance from your system. You can use the E400 in 2-channel mode to run a pair of subs with up to 320 watts RMS each, or switch to 3-channel mode to run your front speakers and a single sub.

What vacuum tubes do for the sound

Many musicians and audiophiles will tell you that tube amplifiers sound better than solid-state designs. Tubes and transistors react differently to the intentional distortions in rock music, for example — transistors try to reproduce it exactly, while tubes tend to smooth out the rough edges while keeping all the details in clear focus. Music seems to sound more alive and "warmer" with tubes in the signal path, creating a more convincing illusion that the musicians are in the car with you. And the reassuring glow of the tubes, visible through a window on the amp's top, adds a nice touch as your friends check out your system.

Product Highlights:

  • 4-channel car amplifier
  • 110 watts RMS x 4 at 4 ohms (160 watts x 4 at 2 ohms)
  • 320 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)
  • dual triode vacuum tube driver stage
  • Class AB design
  • separate front and rear variable low- and high-pass filters (40-250 Hz)
  • preamp and speaker-level inputs
  • speaker-level inputs require an optional adapter
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • fuse rating: 25A x 3
  • 18-1/2"W x 2-5/16"H x 9-1/8"D
  • warranty: 2 years
  • Our 60-day money-back guarantee

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.

Helix E400 Reviews

Average Customer Review:

1 Review

Too Bad (For You) It's been Discontinued

Written by: JayBlay from Windsor Mill, MD on September 16, 2013

Crutchfield Customer Review (What's this?)

I have been kinda conditioned to expect some certificate certifying what an amp's true power is, so I was surprised when I peeked into the box to see that the only paperwork was a set of instructions. This amp...I have no idea what it's true power rating is, but I can tell you that the 110x4 that is listed on the box is extremely conservative. It is pushing two sets of Alpine SPR-60C's to their limits (although I suspect that is a partial function of trying to get the tuning right). In any event, there is something sexy about being able to say that I have a vacuum tube amplifier in the car and I guess I got the very last brand new e400 that Crutchfield had available. It is definitely a very clean and powerful amp and I know I couldn't have done any better given the sale price I got it for at the time of purchase. It is a shame that Helix opted to get rid of their middle of the line offering and also a shame that their competition series does not incorporate vacuum tubes.

I'm having a Punch p300x2 (also purchased from Crutchfield) in a few days to power an 8" R-type sub and I cannot wait to hear how all of the speakers play together.

Pros: Clean and powerful, exclusive, cool factor, great price.

Cons: If you could call it a "con," the amp is way more powerful than the stats let on.

Hands-on research

What's in the box?

Download owner's manual

  • Four-channel amplifier
  • Six 25 amp ATO fuses (3 installed/3 spare)
  • Four 3/4" Self-tapping screws
  • 5mm Allen wrench
  • 2.5mm Allen wrench
  • Instruction manual (German/ English)

Product Research



Tube Preamp Stage: Two dual triode vacuum tubes are used in the preamp stage for warm and powerful sound reproduction.

Speaker-level Input: High-level inputs can be used when the source device doesn't have preamp-level outputs. The same RCA inputs on the amp are used for either speaker-level or line-level connections. When a speaker-level signal is used, speaker wire-to-RCA adapters are needed (item number 20609ZISL or 136XDCLR2S, sold separately) and the Input Select switches should be set to high.

2-Ohm Stable: In stereo mode (powering four speakers) the amplifier is stable down to 2-ohms. The 2-ohm output is 160 Watts RMS x 4 channels.

Bridgeable: The E 400 can be bridged to two channels, outputting 320 Watts x 2-channels into 4 ohms. You can also wire the E 400 in three channel mode, bridging half the amp and running the other half in stereo (110 Watts RMS x 2 channels plus 320 Watts x 1-channel).

Protection Circuitry: The E 400 offers four protection circuits: short circuit (or too low an impedance on the outputs), thermal overload, over voltage, and under voltage.


4-Channel: The amplifier is divided into two sections, channels 1/2 and channels 3/4. Each pair of channels has independent gain, crossover, and input level controls.

Crossover: The built-in crossovers have three position switches to select the crossover operation as high-pass, full-range, or low-pass. The crossover points are continuously variable from 40 to 250 Hz.

Input Select: The input level control is switchable; set to Low when connecting line level input signals and to High when connecting speaker level signals.

Gain: The rotary gain controls are continuously variable from 0.4 volts to 6.0 volts to match the source signal.


Power: The power and ground inputs are set-screw terminals; they will accept bare wire up to 2-gauge (HELIX recommends 4-gauge minimum) and are tightened/loosened with the included 5mm Allen wrench.

Remote: The remote turn-on input is a set screw terminal; it will accept bare wire up to 8-gauge and is tightened/loosened with the included 2.5mm Allen wrench.

Speaker Outputs: The speakers connect to four pair of set-screw terminals; they accept bare wire up to 8-gauge and are tightened/loosened with the included 2.5mm Allen wrench.

Signal Input: Two pair of stereo RCA jacks connect to the output signal from the head unit. The RCA jacks will accept line level signals, or speaker level signals (requires speaker wire to RCA adapters, sold separately).

Fuse: The amp is protected by three 25-amp ATO-type fuses.

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 verify what’s in the box, 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.