Mobile Electronics Australia

If you’re serious about signal processing then one of these two magic ‘black boxes’ simply must be on your shortlist. Whether it is an OEM integration task, dramatically improving your car’s sound quality, or both – Alpine’s PXA-H800 and Audison’s Bit One are the best processors on the market today. So, how do they compare?

The little black box has come a long way in the past few decades. Early generation source units and amplifiers offered very little built-in signal processing, so external analog processors were placed in the signal path to facilitate tasks like pre-amplification, crossover filtering and equalization. Then manufacturers got smart and built these signal processes into the sources and amplifiers themselves. This worked fine for about a decade while we all relied on CDs for playback.

Fast forward to today and we’ve come a long way as consumers. For the majority of us music is stored digitally on portable devices like iPods or iPhones, our smart phones need to be connected to the car for hands-free calling, plus our cars have gotten more advanced too. Many new vehicles cannot be retro-fitted with aftermarket source units, and don’t easily adapt to accept additional aftermarket amplifiers – making system expansion troublesome. Likewise, serious audiophiles are demanding higher fidelity as well as higher levels of signal processing than ever before.

Enter the modern age of the external signal processor, which has been designed to tackle all of these tasks all-in-one while using the latest digital technology. Being digital makes both Alpine’s PXA-H800 and Audison’s Bit One processor far ‘cleaner’ devices, meaning that they are less prone (but not necessarily immune) to extraneous noises or interference from the other electronic gadgets in your car. This was the main bugbear of the archaic analog black-box processors.

Another problem solved by digital processors is processing power, accuracy, fidelity and flexibility. Once the input signal has been converted into the digital realm it is theoretically free to be manipulated without fear of degradation. With both of these devices it is even possible feed in one or more digital music streams, or even a multi-channel surround signal in the case of the Alpine unit - while the Audison can feed the processed digital signal on to matching amplifiers as an output digital stream as well. This level of signal manipulation and inherent retained signal integrity was the stuff of dreams only a few years ago.

Each of these devices goes about its tasks in a similar manner, having been designed to sit between the OEM or aftermarket source and your amplifiers to facilitate a myriad of comprehensive signal processing. These functions include pre-amplification, equalization, time correction and crossover filtering.

Both can be controlled and tuned via a PC, both can be commanded via a dash-mountable controller, while Alpine’s PXA-H800 has the added bonus of integrating with certain Alpine source units. Both also cost just under $1200 all up if you include the optional RUX-C800 commander for the PXA-H800, though if you have an Alpine compatible source you can save yourself $299.

The question we all want to know is; which one should you choose? Let’s break down the individual attributes of each device one by one for a direct comparison.

The key difference here between the PXA-H800 and Bit One is that the Audison is strictly a standalone signal processor that can only be tuned via a PC, whereas the Alpine can be tuned via PC or via the optional RUX-C800 dash mountable controller. The Audison Bit One does come with their DRC dash controller unit, though its function is simply to act as pre-amp control for things like volume, fader, balance, subwoofer level and switching sources or pre-set tuning regimes.

Further to this, the PXA-H800 can be linked to any number of premium level recent model Alpine CD tuners, Media Receivers or multi-media A/V Receivers spanning the last half a decade or so – which is good news if you already own an Alpine source. However, the actual tuning of the advanced processing still requires either a PC or the RUX-C800, leaving control of just the pre-amp tasks via the Alpine compatible source unit.

Alpine have also outfitted the PXA-H800 with a microphone port that works with its automated IMPRINT self-tuning system for setting equalization and time correction. This will be handy for novice users, though conducting the tuning with the aid of a proper real time analyzer by an experience installer will always yield better results. Sadly, the pre-used test sample of the PXA-H800 I was sent came without the microphone so I wasn’t able to test this aspect first hand. I have used Alpine’s automated system before though, and it is a very simple process of following on-screen prompts.

The Audison Bit One is designed purely for self-tuning, so if you’re going to get the most out of this device you’ll either need to learn some basic tuning skills or pay an experienced installer to tackle this for you.

It’s never what I’d call a ‘simple’ task to integrate devices like these into your system, but it is straight-forward. Both units require power, earth and trigger connections. Alpine’s system is a source unit style plug-in loom with flying leads that also provides an audio input for navigation commands when used with certain Alpine A/V source units.

The Bit One, meanwhile, features small plug-in docks that each feature tiny insert terminals that have flat head type screws to clamp the wires. This is certainly compact, but they’ve placed the power and earth about one millimeter apart which lends itself extremely well to short circuits. Make sure you fuse this. Audison do kindly provide three triggered inputs depending on how you want to turn the unit on or off, for example with the key, via a triggered remote of an aftermarket source, or what have you. Both units have a triggered output which is used to turn on and off any amplifiers in the system to avoid on/off pops.

The Bit One has a slightly more flexible input stage thanks to offering 6-channels of RCA inputs, 6-channels of speaker inputs, two pairs of analog AUX inputs, plus a speaker level ‘PHONE’ input if you have an aftermarket hands-free system. On top of this you get dual digital inputs with one toslink and the other coaxial. It’s worth noting, however, that Alpine don’t really need a phone input for a hands-free system since they assume you’ll simply use a Bluetooth equipped Alpine source or an OEM based Bluetooth system. Fair enough.

The PXA-H800 6-channel analog inputs double as speaker level inputs thanks to some supplied adaptor cables. These inputs are arranged as three stereo pairs that can be linked (front/rear/sub input), split into separate groups (AUX1/2/3), or even arranged as a 5.1-channel surround input. Adjacent to these inputs are a pair of Ai-Net proprietary ports that are each linked to toslink digital inputs. These allow you the choice of connection to an Alpine source and CD Changer (people still use those?!?!), or you can use each digital input for standalone sources. An example of this would be a modern BMW OEM source that can be modified to offer a digital output signal, and Audison Bit One’s digital inputs can be used in this manner as well.

The Bit One is strictly a stereo-only device, and its digital inputs can only process S-PDIF 48kHz/24 bit signals, whereas the PXA-H800 has been designed to work with multi-channel input streams from DVD sources and can process Dolby Digital and DTS formats. Furthermore, stereo input can be processed for Dolby Pro Logic II to emulate surround effects.

For outputs both units feature a total of eight channels, with the Alpine arranged into four stereo pairs that can be switched to 5.1-channel surround with the extra two outputs likely used to split front signal into mid/tweeter sets per side. The Bit One’s outputs are assigned to the more straightforward three sets of stereo outputs plus subwoofer outputs. Both units can control and facilitate the most common speaker arrays which will be tweeter/mid front pair, rear pair, plus subwoofers, or active 3-way front stage plus subwoofers.

Looking at the measured specifications of each unit reveals more or less equivalently excellent specs across the board. All input types can handle any voltage range you could throw at them, while output of up to 4VRMS is more than ample. Obviously the noise floor will be most quiet via digital means but while S/N ratios of 112dB look bloody impressive that fact is if there’s audible noise in your system it won’t be the fault of either processor regardless of the input type.

One other differentiator is the Bit One’s AD Link output, which is designed to send the now freshly processed multi-channel signal to Audison’s own voce or Thesis series amplifiers for D/A conversion downstream. In this manner the Bit One is more future-proof than Alpine’s PXA-H800, albeit only when using Audison amplifiers thanks to the proprietary system they’ve employed…



Both units come equipped with two compact discs each. One provides the test tones for use in the vehicle source during set-up or when tuning, while the other contains the PC-based control software and installation programs plus – in the case of the Bit One – a pdf owner’s manual. Alpine are still generous enough to provide a booklet owner’s manual which is always easier to read than a pdf document. Trees be damned I say.

Installing the Audison system requires the installation of both the software itself plus the drivers for the Bit One to be accessible by the PC, and these need to be installed individually – which threw me at first until I did the non-man thing and RTFM.

With the outputs to my amplifier disconnected I powered the Bit One up and connected the supplied USB cable to my PC. Double clicking the desktop icon I was greeted by a simple step-by-step set up program to initialize the Bit one’s basic inputs and output to suit the source and amplifier assignments of my car. Simple questions are asked for inputs and outputs, after which you’re prompted to insert the test CD to play track 1, which in turn allows the Bit One to assess the nature of the incoming signal from whichever source you happen to have. Here it uses up to 31-band of digital EQ to provide a flat pre-signal prior to processing. Once done you are greeted with the main control and tuning screen and you can power down the system and connect the amplifiers prior to reconnecting to begin tuning.

Alpine’s system is quite similar, and guides you through choices for system speaker configuration, input configuration, and a choice of high or low range signal input levels. There’s no scanning of the factory system’s input signal using the test CD, however, plus there’s no specific mention of which RCAs are used on the output for which signals.

My first head scratching moment came when the blue illumination ‘cube’ on top of the PXA-H800 refused to come on even though I had 12V at both of the power and trigger inputs as well as an earth. I took the unit to my test bench instead where powering it via my Jaytech power supply showed that the unit was indeed drawing 0.9-amps of current even though the blue light was not illuminated. It wasn’t unit I patched in the USB cable and launched the Sound Manager program that the PXA-H800 winking into life. Hey Alpine, any chance of just letting the cube come on when power is connected? Cheers.

A second cause for pause was when determining the output connections to my amplifier. Unlike the Bit One the PXA-H800 doesn’t prompt you to assign specific outputs, so some plugging and re-plugging of RCAs is required until you work out which pairs of channels are feeding front, rear, subwoofer or what have you.



Once into the main control screen of the Bit One’s program you are greeted with a myriad of windows and tabs to choose from. These allow simultaneous access to the crossover, time delay and graphic EQ functions, while the central ‘Channel Map’ window lets you choose which individual output channels you wish to vary. Via tabs on the top left of screen you can access the EQ settings for each external input source, as well as individual channel output levels. Once you’ve concluded tuning you can save each tuning regime onto your PC, with up to four pre-set tuning regimes that can be uploaded to the Bit One itself at any given time.

These pre-set memory tuning pre-sets can be switched between via the supplied dash mounted DRC controller, which is a compact and beautifully crafted unit finished in brushed alloy. It is illuminated in red and blue, which looks nice but doesn’t match many vehicles on the market like mine.



A small integral LED screen prompts your adjustments, with basic pre-amp control at your fingertips. The idea is to have master volume control done via the DRC’s main rotary commander, with each individual external source’s own output always set to its maximum possible without clipping. This, of course, allows the lowest possible noise floor, but it’s no guarantee that your mates/wife/kids won’t still reach for other volume controls when it suits them – so you’re constantly checking the other input volumes regularly. It also negates the use of OEM steering wheel volume controls.

The main tuning screen for Alpine’s PXA-H800 is again similar but different, and in my view a considerably more elaborate visual feast to work with. Again tabs and windows give you access to all manner of signal processing tasks, though the Alpine system takes greater advantage of the computer menu to offer more elaborate diagrams of what’s happening while you’re tuning.

In the crossover mode, for instance, you can choose filter frequencies, slopes and channel output levels via either drop down windows or by simply placing your cursor over the associated diagram and ‘pulling’ the curve to how you’d like it. Likewise, the Parametric EQ screen lets you grab an EQ band and push or pull it to whatever frequency and boost level you’d like. It’s a complete joy to tune with and will have you grinning like an idiot the first time you use it.

Alpine’s RUX-C800 dash mounted controller is certainly a boon compared to the DRC offered by Audison for the Bit One, as it not only allows control over per-amp functions like volume, fader, balance and subwoofer level control, but also allows tuning of all the PXA-H800’s signal processing parameters. There’s also a detailed OEL screen and the choice of blue or red primary illumination (pity I need green…). As its default display the RUX shows you the internal temperature of the PXA-H800 itself (not outside temp as some MEA posters have assumed) as well as a handy voltage meter. If wired to the same terminals as your amplifier it is a great way to monitor true voltage to ensure your amplifiers are being fed decent power from the charging system under all conditions.

Both units offer an incredible selection of crossover arrangements, filter points and slopes, though from a purely technical perspective the Bit One offers a more flexible arrangement thanks to steeper 42 and 48dB per octave filter slopes. There are also 10 additional filter cut off frequencies to choose from between 20Hz and 20kHz and you get a choice of Linkwitz or Butterworth filter alignments. This said; I doubt these added options will make a dramatic difference to any results you’re likely to achieve. Both systems can be considered virtually limitless in their tuning ability.

Audison’s system gives you a full 31-bands of graphic EQ for each individual input source – which is completely separate from the output EQ applied for tuning the frequency response of the system once the amplifiers and speakers are connected. A separate menu allows you to manually tune this system, whereby you would apply pink noise via the external source and output this into a real time analyzer via direct connection to the output RCA of the Bit One. For output EQ you then get 31-bands of GEQ for each and every output channel. All EQ bands offer plus or minus 12dB of variance.



The Alpine PXA-H800 gives you the choice of graphic or parametric EQ tuning. In GEQ mode there are 31-bands for each of the six output channels, while the PEQ system uses 10-bands and the same 31 frequencies as choices of corner frequency. For Q-filtering you can vary the width of each PEQ band between 0.5 and 5.0 in 0.5 increments.

Both systems have an added EQ system to combat the changing background noise issues associated with driving under different conditions and road speeds. Alpine’s system is called Road EQ, and uses a microphone to compare the noise inside the cabin to the actual music signals being fed into the PXA-H800. While kind of cool, it means leaving a microphone connected at all times – which seems a little impractical to me. Audison’s is called Dynamic Equalization and is a manually tuned system whereby you apply different levels of EQ through differing listening levels. The idea is that at lower volumes you can apply different bass and treble boost to offer a more dynamic sound (the old Fletcher-Munson curve phenomenon at work) compared to moderate and higher volume levels.

Alpine’s system adds their IMPRINT automated tuning regime into the mix as well, which caters for not only output EQ but auto time correction as well. This system relies on the supplied microphone and takes a good few minutes to run through while following prompts on your PC’s screen, as well as changes of microphone position.

Call me old fashioned but I have yet to come across an automated self-tuning system that has been able to arrive at a result that matches what is possible by an experienced tuner by ear and with a proper real time analyzer. As for which EQ system is superior of the two it is quite hard to say. I like the choice of PEQ from Alpine but then again I like the option of input EQ for each dedicated source from Audison. Again, either system will achieve similarly excellent result in the hands of a good installer.

When it comes to aligning each output channel both Audison’s and Alpine’s systems offer ample delay for each of their channels. Unless you’re trying to align a system installed into a Greyhound Bus I’m sure around seven meters of delay should suffice. The notable differences between the two systems? Well, again Alpine offers an automated route via IMPRINT, but again I’d implore you to perform this manually or have an experienced tuner do it for you.

With all the major important aspects discussed and compared we can now have a look at any final differentiators between the two DSP systems. Both are equally well built and use high grade internal construction and components throughout. Both are of roughly similar size too, though the Bit One is about half as narrow as the PXA-H800.



Audison’s AC Link system comprises a CAT 5 cable output for up to 8-channels of digital output signal instead of using the analog RCAs. This system relies on having either Thesis amplifiers or the new voce models with the required digital input stage modules added.

As an alternate sweetener, Alpine offers its Euphony system for the PXA-H800. According to their website, “Euphony makes it possible to enjoy 5.1-channel sound from 2-channel sources. It creates natural surround sound from CD or iPod with wider soundscapes and harmonics. It specially enhances vocal and instrumental quality, for a superior sound field and no listener fatigue.” Personally I’m not a fan of such systems, but you might find the results of Euphony to your liking.



If you’ve decided to skip reading this full comparison and have simply jumped to the conclusion I’ve got bad news for you. The only way to really tell which system is better for you is to know each system’s features intimately and then compare that to your system’s specific needs. This comparison was never about choosing a winner or loser, as both Alpine’s PXA-H800 and Audison’s Bit One are both exemplary devices that deserve equal praise. Put simply; there’s no bad choice here.

Having taken the time to install both units into my test vehicle during this review I can report that both worked flawlessly, were absolutely silent, and aside from the added processing they could apply were for all intents and purposes completely transparent when placed into the signal path. You can’t ask for better than that.

Audison’s incredible Bit One unit benefits from being more tightly focused as a pure stereo device. In my view, that makes it the superior stand alone processor as well as the better OEM integration device. It offers a greater variety and number of input and output options first and foremost, and this simply makes it viable to a wider variety buyers. The big caveat is that it has no self-tuning, which is fine for experienced users and installers but a technical headache for beginners and novices. This makes sense given that beginners and novices aren’t likely to be Bit One buyers, and by the time you’re ready to tackle this level of sophistication the on-screen menu system of the Bit One will make tuning relatively simple.

While it is still an excellent stand alone processor and works awesomely well as a stereo device, I see the Alpine PXA-H800 being more appealing to those of you who already own a compatible Alpine source unit or have desires on a multi-channel surround system. As an upgrade module it offers a staggering array of tuning tools, and I think its PC based interface is the better of the two systems. PXA-H800 is also a better choice for novice users who will rely on automated tuning for things like time correction and equalization and who don’t have access to an RTA. That’s actually the vast majority of you. Also, I reckon a lot of dealers will prefer the Alpine system purely for this reason as well, since most don’t own an RTA either.

That both processors are available at reasonable prices today is the real revelation, and both the Alpine PXA-H800 and Audison Bit One offer the ability to unlock exceptional sound quality if you are truly serious about great sound. Importantly, I don’t foresee any great technological leap any time in the next decade. That means both units are essentially future-proof, and that makes them all the more appealing because they’ll serve you for well into the next decade and beyond. In an age when an iPhone is past its used-by date after 12 months that’s pretty amazing in itself!