Helix P SIX DSP MK2 Review: Mighty, but Outdated

Short answer: the Helix P SIX DSP MK2 is a well-regarded, compact six-channel Class D amplifier with a built-in eight-channel DSP, but it is no longer the model to look at first. Audiotec Fischer lists it in its product archive, and the company's current flagship in the same case is the P SIX DSP Ultimate. The MK2 makes sense mainly if you find a genuinely new, warrantied unit at a price clearly below the Ultimate and you accept an older feature set. I could not verify a current MK2 price, so this review leans on specifications and independent test data rather than on a price comparison.

How this review was made

This is a specification and research review. I did not install, listen to or measure this amplifier, and nothing here is hands-on experience. It draws on Audiotec Fischer's product page and manual, a February 2016 lab test by the German magazine Car&HiFi (the copy I read is hosted by the manufacturer, which is worth keeping in mind), the manufacturer's pages for the P SIX DSP Ultimate and M SIX DSP, a retailer page for the JL Audio VX600/6i, and a few owner forum threads that I treat as anecdotal. Sources were checked on 12 October 2026. Anything I could not confirm is left out or marked as not confirmed. Statements about sound are attributed to the magazine's listening notes and measurements, not to my own ears.

Design and build

The MK2 uses a solid aluminium case measuring 50 x 260 x 190 mm (height, width, depth), low enough to fit under many seats. A weight was not published in the sources I could verify. The casing carries a clipping LED and a fuse-status LED, and inside sit three 20 A mini fuses. Car&HiFi called the amplifier mechanically and electronically at its best and noted that the power supply uses a step-up converter instead of a transformer. It also pointed out that the board has five power-stage chips: four serve channels C to F, while A and B share one. That sharing is why channels A and B are limited to 4 ohms while C to F tolerate 2 ohms.

The input-range jumpers sit inside the case; changing them means removing ten screws from the bottom plate, per the manual.

Features and usability

The amplifier takes six RCA channels, six high-level (speaker-level) channels and one optical S/PDIF input. The high-level inputs use Audiotec Fischer's ADEP circuit, designed so that factory radios that monitor their speaker outputs do not raise fault messages or drop functions such as the fader. Input sensitivity is set per channel pair with three potentiometers, with factory ranges of 2 to 4 V for RCA and 5 to 10 V for high-level; the internal jumpers move those to 4 to 8 V and 10 to 20 V. The optical input accepts uncompressed stereo PCM from 12 to 96 kHz only, so Dolby and compressed streams are not supported, and there is no coaxial digital input (the Ultimate adds one).

Outputs are six speaker channels, two processed RCA outputs at up to 3 V RMS for feeding another amplifier, and two remote outputs. Counting those two RCA outputs, the DSP handles eight processed channels. Car&HiFi lists a 30-band parametric EQ per channel (+6 to -15 dB, Q 0.5 to 15), several crossover alignments up to 42 dB per octave, phase adjustment in 11.25-degree steps, and time correction from 0 to 318 cm in 3.5 mm steps, plus a real-time analyser that needs an optional measurement microphone. According to the manual the unit stores two sound setups, switched with a button on the amp; the Ultimate stores ten.

Housekeeping features include a Power Save Mode that switches the output stages off after 60 seconds without a signal (adjustable in the software), tolerance of supply dips to 6 V during cranking, automatic switching to the optical input, and 12 V or 24 V operation with the same rated performance. A HELIX Extension Card (HEC) slot accepts optional modules; the manufacturer lists a Bluetooth streaming card, an aux input card, an optical card and a high-resolution USB audio interface. Bluetooth is not built in, and fitting a card means swapping a side panel.

Setup is done on a computer through Audiotec Fischer's DSP PC-Tool over USB. The MK2 page links the version 4 download; whether newer tool versions work with the MK2 is not something I could confirm.

Sound and performance

Everything in this section comes from manufacturer numbers and the Car&HiFi test. None of it is my own listening. According to the magazine's lab, the two small channels delivered about 116 W each at 4 ohms and the four large channels about 123 W, against a rating of 120 W. At 2 ohms the large channels managed roughly 195 W each, below the 230 W rating but still a large figure for an amplifier this size. The magazine measured an average signal-to-noise ratio of about 91 dB, lower than the 100 dB (analog input) and 105 dB (digital input) the manufacturer claims, although the conditions behind each figure are not spelled out. Distortion was described as comfortably low, though not at the level of the company's analog Brax amplifiers; I found no numeric THD+N table in the text I could read.

The 2-ohm shortfall deserves a note. At 2 ohms the measured 195 W is about 15 percent below the 230 W rating, while the 4-ohm results sit within about 3 percent of the 120 W rating. Test conditions differ between labs, so read the headline rating as an upper bound rather than a promise.

The magazine's listening notes describe a tonal balance that is neither too warm nor too cold, an easy character at both low and high volume, and precise bass and dynamics. It rated the amplifier top-notch overall and called it the digital reference. Two caveats: this was a 2016 test of a then-new product, and the manufacturer-hosted copy suggests a favourable selection. Owner forum posts I read were mostly positive about the DSP section, while a few owners prefer class AB amplifiers for tone; those are individual opinions, not measurements.

The magazine also noted that the MK2's Texas Instruments power chips allow the full 44 kHz bandwidth, but the extremely high damping factors of the first-generation P SIX DSP are gone. The manufacturer's spec sheet still lists a damping factor above 100.

Setup, installation and daily use

This is not a beginner's plug-in amplifier. The manual recommends an authorised Helix dealer and links full warranty coverage to proper installation. The list below summarises the manual; it does not replace it.

• Disconnect the negative battery terminal first. Fit a main fuse in the positive cable within 30 cm of the battery, sized to the total current of the whole audio system. The manual gives the amplifier's own figure as a maximum of 60 A RMS on 12 V and 30 A RMS on 24 V.
• Use at least 16 mm² (AWG 6) power cable for runs under 1 m and 25 to 35 mm² (AWG 4 to 2) for longer runs. The ground cable should be the same gauge and go to bare chassis metal or the battery negative.
• Never use the RCA and high-level inputs at the same time; the manual warns this can damage the radio's outputs. Connect the REM line to the radio's remote output when using RCA or optical input, and avoid switching it from the ignition because of on and off noise.
• Match input sensitivity to the source before connecting speakers. The manual describes using a 1 kHz test tone and the clipping LED.
• Configure the DSP, especially crossovers, before connecting speakers. The manual warns that a wrong setup in a fully active system can destroy tweeters.
• A digital source normally has no volume control, so the optical input can deliver full level at every output. The manual strongly advises an optional remote for volume.
• Respect the load limits: 4 ohms minimum on A and B, 2 ohms minimum on C to F, and no bridging. For subwoofers the manual recommends dual-voice-coil drivers.

Mount the amplifier on a solid surface with airflow, and check behind the mounting area for wiring, brake lines and the fuel tank before drilling. One piece of arithmetic worth knowing: 60 A at 12 V is about 720 W of electrical input, which is less than the 1,160 W you get by adding every rated channel output (2 x 120 W plus 4 x 230 W). The manual does not state the conditions behind the 60 A figure, so read the per-channel ratings as individual capability and size the electrics for how you actually listen.

In daily use the amplifier turns itself on from a high-level signal or the REM line, drops into Power Save after 60 seconds of silence and wakes again within about one to two seconds (the product page says one second, the manual says two). The manual also notes that some CAN-bus cars keep the radio running "invisibly" for up to 45 minutes after you leave, which is where Power Save earns its keep.

How it compares

The table uses manufacturer specifications. Ratings from different brands use different test voltages, so treat cross-brand power figures as indicative.

Spec	P SIX DSP MK2 (reviewed)	P SIX DSP Ultimate	HELIX M SIX DSP	JL Audio VX600/6i
Amplifier channels	6	6	6	6
RMS per channel at 4 ohms	120 W (A to F)	120 W (A to F)	100 W	75 W (14.4 V)
RMS per channel at 2 ohms	230 W (C to F only)	230 W (C to F only)	100 W	100 W (14.4 V)
Bridged output	Not allowed	Not rated	3 x 200 W at 4 ohms	3 x 200 W at 4 ohms (14.4 V)
DSP	8 channels, 64-bit, 1.2 billion MAC/s	12 channels, two 64-bit DSPs, 2.4 billion MAC/s	10 channels, 64-bit, 1.2 billion MAC/s	Triple-core AKM DSP; channel count not confirmed
Sampling rate, bandwidth	96 kHz, 20 Hz to 44 kHz	96 kHz, 10 Hz to 44 kHz	48 kHz, 20 Hz to 22 kHz	Not confirmed
Digital input	Optical (12 to 96 kHz)	Optical and coaxial (to 192 kHz)	Optical (12 to 96 kHz)	2-ch S/PDIF in (to 192 kHz) and out (96 kHz)
Processed RCA outputs	2 (3 V)	4 (3 V)	4 (6 V)	2 (4 V)
Size (H x W x D)	50 x 260 x 190 mm	50 x 260 x 190 mm	50 x 320 x 154 mm	Not confirmed
Price context, 12 Oct 2026	Not verified	EUR 1,499 at one EU retailer	About EUR 699 (sale price) at the same retailer	Not verified

Against its siblings, the MK2 matches the Ultimate's rated power with a smaller DSP and fewer outputs, while the M SIX DSP trades power and bandwidth for a lower price. The JL Audio VX600/6i rates lower in power but has its own DSP, S/PDIF in and out, and app-based tuning. The MK2's niche is Ultimate-class power and 96 kHz processing at a discount.

Who should buy it and who should skip it

It suits a builder who wants a compact amplifier and DSP in one box, for example an active front stage plus a processed feed to a separate subwoofer amplifier, or an upgrade behind a factory radio using the high-level inputs. It also suits 24 V vehicles, since performance is rated the same on 12 V and 24 V. Skip it if you want automatic EQ correction, an input analyser for factory radios, 12 processed channels, a coaxial input or ten stored setups; the Ultimate covers most of that. Also skip it if no seller can document new stock and warranty.

Buying advice

Because the MK2 is archived, first work out whether the unit is new or used and who is selling it. Ask for the part number (P816002) and serial number, get the warranty terms in writing, and read the return policy. The manufacturer's manual states that warranty follows the legal requirements and excludes damage from overload or improper use. The MK2 listings I saw were mixed: some marked sold out, others from individual sellers whose condition and dates I could not verify.

For price context, one EU retailer listed the Ultimate at EUR 1,499 and the M SIX DSP at about EUR 699 on 12 October 2026, and a US specialist listed the Ultimate at USD 2,100. An MK2 only makes financial sense if it comes in well below the Ultimate, and where that line sits depends on the unit's condition and warranty.

Budget for extras: power and ground cable, a fuse holder, RCA cables or the optional Easy Plug Cable (EPC 5), a computer for the DSP software, a measurement microphone for the analyser, and a remote if you use the digital input. For Bluetooth, confirm the card is listed for the MK2; newer cards sold with the Ultimate are not confirmed to fit.

Final thoughts

I rate the Helix P SIX DSP MK2 3.5 out of 5. The rubric weights performance and sound at 40 percent, features and usability at 20 percent, build quality and design at 15 percent and value at 25 percent. This is a research-based rating: it rests on the manufacturer's data and one independent lab test, not on hands-on use. The weighted score is 3.725, rounded to the nearest half point. The Verdict, Pros and Cons panels on this page summarise the conclusions.

Criterion	Weight	Score	Weighted points	Basis
Performance and sound	40%	4.0	1.600	4-ohm power within about 3% of rating; 2-ohm power and SNR below claims
Features and usability	20%	3.5	0.700	Solid inputs and DSP, but two setups, two RCA outputs and an older platform
Build quality and design	15%	4.5	0.675	Aluminium case, German manufacture, build praised in the magazine test
Value for the price at review	25%	3.0	0.750	Neutral score: no verified MK2 price and a newer model exists
Total	100%		3.725	Rounded to 3.5

Some links on this page are affiliate links; they never affect our ratings. As an Amazon Associate I earn from qualifying purchases.

Sources and further reading

• Audiotec Fischer: HELIX P SIX DSP MK2 product page
• HELIX P SIX DSP MK2 instruction manual (PDF)
• Car&HiFi test, February 2016, as hosted by Audiotec Fischer (PDF)
• Audiotec Fischer: HELIX P SIX DSP ULTIMATE product page
• Audiotec Fischer: HELIX M SIX DSP product page
• Retailer specification page: JL Audio VX600/6i
• Retailer listing used for Ultimate price context