The stunning evolution of a proven range.


Because Alpine is just about everywhere these days many people, especially younger folk, have absolutely no idea just what vast accomplishments lie in Alpine’s past. Therefore I’m going to start this review with a little history lesson. Alpine is a subsidiary of Japanese electronics manufacturer Alps Electric Company Ltd and although it started out in 1967 as Alps-Motorola, it became Alpine Electronics Incorporated (or Alpine for short) in 1978. Alpine has been credited with many accolades in relation to its source units, from the first in-car equaliser in 1982 to the first triple disc head unit in 1993.

But did you realise that its amplifiers are also something special too? Alpine has been designing amplifiers for more decades now than I care to remember and this goes largely unnoticed because of the sheer amount of amplifier brands available today. When Alpine first started manufacturing amplifiers the market was very sparse and many didn’t seem to work for extended periods. But soon enough Alpine units became well known for their reliability in the face of such adversity. This is what has kept it at the

forefront of design and the new PDX range should continue that tradition.


When Alpine released the first range of PDX amplifiers a couple of years back, they were initially received with much excitement. However in this day and age, where there are plenty of dedicated specialist manufactures that are true masters of their trade, this enthusiasm began to wane a little in comparison to the hot competition.

So Alpine returned to the drawing board a year ago, taking the basic PDX design and re-developing much of the technology until it was ready to release the new design as the 2010 PDX range – a vast improvement on the older series and easily on par with the best amplifiers in the car audio world today. I’d heard rumours that the specifications of the new PDX amplifiers were impressive but when the new PDX-F6 hit my desk I must confess I too seemed to have underestimated Alpine’s ability to create a superb amplifier on a tight budget. It seems Alpine is determined to revisit its former glory days as these amplifiers boast the best specs since the F#1 amplifier was available. The PDX-F6 is the larger of the four channel amplifiers (there is a smaller PDX-F4) and there are also two monoblock variants available. It’s a high power digital class-D design and each of its channels is rated at 150 watts continuous at 4 ohm (in compliance with the CES2006 standards). The birth certificate included with this particular one stated that it had been tested to output 182 watts per channel. In other words it’s no lightweight despite having a tiny footprint. Now I might just delve a little into the world of class-D digital amplifiers as the Alpine is a bit special. Most class-D (sometimes known as digital switching) amplifiers contain powerful MOSFETs (Metal-Oxide Semiconductor Field Effect Transistors) that are switched (in that they’re either turned fully on or fully off) by digital control as opposed to raw voltage like say an analogue amplifier would have. This means theoretically that zero time is spent transitioning between the on and off states. In a perfect world this would mean 100% efficiency because if the switches are open then all of the power supplied to them is delivered to the load and none is converted into heat (remember you cannot eradicate energy, only convert it). When the switches are off they’ll have full supply voltage standing across them but no current flowing so again, no heat is dissipated.

Now that is the somewhat simple explanation of the workings and it’s not a perfect world. Therefore, like anything electronic, anything above 90% is considered acceptable. If class-D is so good then why isn’t everyone using it? Well the issue is that the distortion and noise levels are usually higher because the output of a class-D amplifier is basically a square wave form and the smallest irregularity (noise, voltage ripple, etc) results in an irreversible change of the output. Low pass filtering tends to smooth these pulses out and helps to restores the signal shape on the output but only a company like Alpine has the technical ability to produce a full range class-D amplifier that doesn’t suffer from high distortion levels. So basically the PDX amplifiers are not completely ‘digital’ as such because all amplifier power output stages still deal in voltage and current. However the control is binary as opposed to analogue voltage wave forms. They basically keep the signal in the digital realm until just prior to output. They’re definitely full range too, with the frequency response running from 5Hz – 100kHz! The design offers a very respectable 0.003% (total harmonic distortion) taken at 10 watts and 0.05% THD at full song. Signal to noise ratio (which is A-weighted) is 116dBA and damping factor and slew rate are quite high too meaning the amplifier is more than capable of controlling unwanted cone movement and handling high speed dome transients respectively. Compare those specs to many other amplifiers on the market and see who comes out on top.