Despite attaining near legendary status for its speaker designs, French designer Focal also dabbles in other facets of audio, with one particularly strength being amplification. Some would say it’s a natural progression — however, Focal didn’t approach its amplifier designs with such a nonchalant attitude. It spent many years refining its designs, during which time it has offered everything from the ultra-supreme DUAL series, the powerhouse FPS series, and even entry level budgets were catered for via the SOLID series. 
“Perfecting” is an interesting descriptor and indeed one that can sometimes have a nasty sting in its tail. It does not simply symbolise throwing endless wads of cash at a design until its specifications reach beyond the stratosphere. No; the term perfecting must include a fiscal consideration too, and this is where many companies come undone. It’s that same old two-out-of-three scenario we see played out constantly pertaining to amplifiers. Good, powerful, cheap; which two would you like?
More than 2 out of 3?
It’s no secret it would take a clever designer to produce an amplifier that went some way to incorporating all three of these prerequisites. Likewise it’s no secret that Focal is just one such designer. Ergo allow us to present the new FPX range. Primarily Class-D in design, the FPX amplifiers blend copious power output, accurate control and quality build working together harmoniously. The range includes various configurations ranging from a monobloc through to two and four channel designs, however, the engineers put a fork in the road upon reaching the four channel units. 
Being the wise designer it is, Focal recognises the difference between tackling a challenge and tackling the actual laws of physics themselves – the latter cannot be beaten. At some point you must decide whether you’re leaning more towards quality or sheer grunt, and many manufactures surrender at this point because it all gets too hard. Focal therefore has opted to give you the choice; you can stick with the Class-D units for the audio quarter mile or you can opt for sound quality and choose the Class-A/B FPX 4.400 SQ. No prizes for guessing which we’re about to delve into.
Before we do proceed, let’s just lay down a quick crash course on amplifier classes, for its intrinsic to the FPX 4.400 SQ’s design. As you know, analogue amplifiers are classed depending on how much current they flow during each wave cycle (or Hz). Measured in degrees; a 360-degree cycle denotes current flowing the entire time. Class-A switching utilises the same output transistor to reproduce both top and bottom halves of the audio waveform, hence it’s always operating with full current flowing through it, even if there’s no signal. Not only electrically inefficient, this switching also suffers from significant thermal inefficiency. Nonetheless, Class-A amplifiers sound warmer and more natural in comparison to other classes, hence why audiophiles endure these negative phenomena. 
Class-B amplifiers use twin transistors groups with one reproducing the positive top portion of the waveform and the other the negative bottom portion of the waveform, or 180-degree a side. This design is the diametric opposite to Class-A insofar as current is concerned. It’s very efficient due to there being no idle current flowing through the output transistors when there is no audio waveform to reproduce. The detractor here is that all transistors require a small amount of current to turn on and as they’re consuming this power it produces a small step in the waveform to occur. This is not suitable for audio sound quality so necessity has given birth to the best compromise between the two; the Class-A/B switching design. 
These amplifiers also employ two groups of transistors and are fundamentally similar in design to Class-B with the exception of having a small amount of bias current constantly running through the transistors so they remain switched on, eradicating the aforementioned blip in the waveform. Consequently, in employing Class-A/B switching you retain the trademark warm and smooth sound but without too hideous an inefficiency. 
Class-D amplifiers on the other hand are switched on and off digitally, and because of their block-built waveform they’re deemed inferior to Class-A/B insofar as sound quality is concerned, yet they’re vastly more powerful – and ultra-efficient – for a similar footprint because the entire analogue input stage is effectively being replaced with a chipset.
So if its power you’re seeking then you want to opt for the Class-D FPX 4.800, whereas if you’re more of a purist you choose the FPX 4.400 SQ – SQ denoting sound quality. As the part number suggests it’s a 4-channel amplifier whose channels output just over 70 watts continuous when presented with a 4 ohm load, and with a total harmonic distortion of just 0.04 percent. Loading it down at 2 ohms will return you just over 100 watts per channel and even when doing this the distortion still remains exceptional. The unit can also be bridged, offering over 200 watts per channel pair. 
Control over unwanted cone movement and deceleration to the zero point is impressive thanks to a high damping factor of and reciprocating accuracy is maintained thanks to a good slew rate. Ancillary aural specifications are also above average, starting with a high separation equating to very little channel bleed and an equally impressive signal-to-noise ratio giving it a quiet noise floor. Last but not least, frequency response is an impressive 10Hz through to 22kHz.
Focal FPX 4.400 SQ
Looking good
Focal’s amplifiers have always looked the business, although it did go a little avant-garde there with the FPS design. Focal has returned to the more conventional-looking design it has been famous for. The FPX units are finished with a neat looking aluminium case which has been anodised black. Heatsinks are strategically placed for thermal efficiency and the Focal logo is proudly printed on the top. 
Lined along one end are the low level pre-ins along with all aural controls ranging from gain through to high-pass and low-pass crossovers. The opposite end is home to plated power, remote and earth input blocks, in addition to twin speaker output blocks; one for front and one for rear. Twin 30-ampere protection fuses are also housed at this end. Physically it’s not an overly imposing amplifier, with its overall footprint measuring 314 x 175 x 57mm and weighing just 3.7kg.
Focal FPX 4.400 SQ
The FPS 4.400SQ is a very well laid out design, featuring a thick circuited board inherently packed with high quality hardware. The electrical adventure starts with a trio of Samwha 25v 2200uf stiffening capacitors located in and around the input block and fuses. From there the stabilised current is stepped up via a single enormous air core transformer before being stored in four large 50v 1500uf Samwha power capacitors, ready for transferal via 18 audiophile grade Sanken output transistors. 
Naturally, all sound processing and signal path circuitry is kept at the opposite end of the layout, well away from the current handling hardware. In order to achieve a high thermal efficiency the FET’s are clamped along the sides of the heatsinks where the cooling 
fins feature.
Approaching auditioning were fairly substantial expectations, but of a differing kind. Our car normally has a triplet of Focal Dual Direct amplifiers installed, ergo I’m well aware of just what Focal is able to achieve amplification wise. By the same token, they’re multiple times the $599 asking price of the FPS 4.400 SQ. Therefore, I needed to keep some perspective, and when you match this humble amplifier against those similarly priced you’ll find it not only comes into its own but it actually becomes a little pressing for said competition.
Sure, it’s not the most powerful amplifier on the market, nonetheless, what it does offer is not insubstantial either; the control it exudes is beyond impressive for its price. Bottom end sub-bass and midbass notes are tightly controlled and articulate, midrange frequencies have real life and body to them with middle-order vocals presenting richly. The treble is equally accurate too, with the highs come across with crystal clear clarity and without 
the artificial boost many amplifiers lend themselves to. 
Speaking of boosting things; overall the output is quite linear and tonally smooth. Even the noise floor is striking, with it offering little hint of audible hiss until you have the gain right at the pointy end.
The FPX 4.400 SQ may not be the biggest or meanest amplifier on the block, however, this isn’t important for a true sound quality oriented amplifier. What is ultra-important is that it amplifies the sound honestly without adding anything to the original artists’ intention. 
Sounds peculiar I know, but so many amplifiers are so hell-bent on hammering you into oblivion that they’ve long overlooked what it means to perform basic quality amplification. This, my friends, is exactly where the FPX 4.400 SQ shows its mastery. 
Focal FPX 4.400 SQ
Focal FPX 4.400 SQ 4-channel amplifier
Price: $599
+ Focal’s renowned solid engineering
+ Quality chassis and assembly
+ Accurate and clean sound
- As always... more power please?
Type: Class-A/B 4-channel amplifier
Power Rating: 4 x 70/100 watts continuous at 4/2 ohms (CEA2006)
Features: High- and low-pass crossover