Mobile Electronics Australia

When you think about it, an asymmetric power output makes a lot of sense for anyone who’s planning a one-amplifier based system. Invariably you’ll require higher power input for the subwoofer/s in the system than you will for the main speakers, and other companies who’ve dabbled with this type of amplifier design over the past decade include Alpine and Digital Designs – though neither company offer such a design in their current line-ups.

At $399RRP, the XM-GTR4A exists in a price range that is mainly concerned with first time amplifier buyers. Furthermore, they’ll probably be pretty young (under 20 years of age) and therefore they’ll want an impressive slab of an amplifier so they feel they’ve spent their savings wisely.

They’ll also want something from a trusted name brand, and when we look at the sub-$400 offerings from Sony’s rivals at Pioneer, Kenwood, Alpine, JVC and Clarion it becomes instantly clear that the XM-GTR4A holds a significant power output advantage. The best you’ll get elsewhere will be 60WRMS x 4 at 4ohms from most of these brands (Alpine will give you 50WRMS x 4), whereas the XM-GTR4A will serve up 60WRMS x 2 from the front channels plus a whopping 125WRMS x 2 from the rear channels – all at 4ohms. In bridged mode, the rear channels will provide a lustier 340WRMS x 1 to power a 4ohm load of one or more subwoofers, and this is as much as 3dB or more louder than its price point rivals. For a young bass enthusiast 3dB of bass is a lot of bragging rights!

That extra power does obviously come at the expense of larger real estate, and the footprint of the XM-GTR4A is pretty large at 42cm x 25cm, with a depth of 5.5cm. Taking a peek inside the XM-GTR4A reveals quite a lot of extra heat sink girth that extends beyond that of the single-sided PCB board. Instead of flipping the power supply and output MOSFETs on their ends to reduce the size of the footprint they’re laid out flat against three sides of the PCB. While this is probably the least space efficient way of building an amplifier it does bode particularly well for cooling efficiency. A small thermo fan resides in the end of the chassis at the power supply side, and when combined with the massive and heavily finned cast alloy heat sink I don’t see anyone having thermal shut down issues with this amplifier in any great hurry.

It’s obvious that the XM-GTR4A was never intended to have its internals shown off, and while they may not be all that pretty the overall layout and quality of the single sided PCB and its components are certainly par for the course at this price range.

Sony knows all too well that a striking outward appearance is far more important for younger buyers, and in this context the XM-GTR4A is a winner. I dig the cast alloy heat sink’s gutsy and rugged looks. It’s a great meld of old-school tough meets new school industrial design, with a trick blue illuminated strip right in the centre to highlight things further.

Features & Specifications

The most common wiring application of this amplifier will see it produce 460WRMS of total power in ‘3-channel mode’, where two channels power 4ohm stereo full range speakers and two channels are bridged into a 4ohm load for subwoofers. This falls rather short of the ‘1200W’ number promised boldly on the top of the amplifier itself, but again, buyers in this demographic seem impressionable by such boasts.

The front channels can also be driven into 2ohm loads, which could be a typical arrangement when similar pairs of front and rear speakers were paralleled to each side. Under this guise you’ll get 80WRMS x 2 and therefore, a genuine ‘maximum’ total power output of 500WRMS. These power ratings are taken at 14.4V, and while Sony don’t provide ratings at lower voltages they do advise that these ratings adhere to the CE2006 measurement standard – which means less than 1%THD is present at these outputs.

All the amplifier’s connections and controls are placed along the lower leading edge of the chassis. While the connections are the basic screw down type, Sony has provided gold plated terminals and the power and earth connections will accept up to 8-awg wiring happily. A rubber protective cover is also supplied that slips over the terminals after they’ve been connected.

You’ve got the choice of either RCA or speaker level inputs, and the latter also engage an automated turn on/off circuit that doesn’t require a dedicated trigger to make OEM system upgrades a lot easier. The RCA stage can accept input voltages of between 300mV and 6V, which is a wide enough range to happily cater for any aftermarket source on the market.

The front channels offer a 12dB per octave high pass filter, while the more powerful rear channels offer a 12dB per octave low pass filter – both with a variable cut off range of between 50Hz and 300Hz. Both pairs of channels can be driven full range from 20Hz to 20kHz, while the rear channels have a selectable sub-sonic high pass filter fixed at 15Hz. Finally, the rear channels also have a bass boost EQ that is centered at 40Hz and offers variable boost of up to 10dB.

The combination of the XM-GTR4A’s asymmetric power output arrangement and crossover design make this amplifier suited to very specific speaker arrangements. While the obvious full range and subwoofer speaker arrangement will likely be the most commonly used, the rear channels are equally suited to powering larger full range speakers like 6x9s which often don’t require a HP filter when a subwoofer is not used in the system design. Likewise, it would be possible to drive a pair of stereo midbass drivers in a 3-wayfront stage system using the rear channels with the LP filter set close to 300Hz, while the front channels drive a smaller 4-inch 2-way component set with the HP filter set at 300Hz. When combined with Sony’s matching XMZZR3301 600WRMS (at 2ohms) mono amplifier to power a subwoofer array this would make a formidable and very affordable power combination.

Road test

I wired the XM-GTR4A into my test vehicle and decided to arrange the channels into what will be the most common arrangement, with the front channels powering my Focal Be Kit No.7 components and the rear channels were bridged to power a single 12-inch 4ohm Almani subwoofer in a slot ported enclosure. Twisting the ignition key saw the XM-GTR4A fire straight into life without a thump, click, pop or murmur of any kind, and I was immediately greeted by appropriate output from all channels.

After a few moments of back and forward to check input levels and set the crossovers I arrived at a LP filter of 80Hz and a lower HP filter point of 50Hz (the Focals prefer to play low), while I added a slight tickle at 40Hz via the bass boost and set the sub sonic filter on since I was using a ported enclosure.

For this audition I ran through a specific number of tracks that would test the mettle of the XM-GTR4A and see if its power output was what I’d consider appropriate for what’s promised. This entailed a few classic rock cuts that stressed the dynamic output of all channels to see if decent output levels could be achieved without overly compressing the headroom. Here I focused on the snare drum attack and tonality as well as the bass drum’s weight and authority during the intro to Extreme’s song ‘Cupid’s Dead’ from the album Three Sides to Every Story. I then followed this with a few select cuts from George Michaels’ classic album Older, which serves up some more delicate tunes that accentuate the higher register when combined with low, deep rolling synth bass lines.

Throughout all the auditions and another half an hour of random tracks from diverse sources like Michael Jackson through to Taproot and Stone Temple Pilots I was able to get a good gauge on the XM-GTR4A’s true capabilities. In summation it’s transparent, noise free and serves up enough usable grunt to certainly consider its rated power to be accurate. Furthermore, with a total of 500WRMS on tap from the amplifier’s power supply I’d have to agree with Sony’s power spread between channels given the amplifier’s targeted usage. It sounds damn fine indeed.

Conclusion

Sony have aimed the XM-GTR4A directly at first-time amplifier buyers by placing the emphasis on its big brawny external appearance and a big boast of power output right there on the top of the chassis. It screams ‘lots of amplifier from a brand you trust and for a great price!’ to novice buyers in no small manner. Fortunately the real world performance certainly backs up what they’ve paid for, and while ‘1200W’ is a gross overstatement I know that even 60WRMS x 2 and 340WRMS x 1 into 4ohms will probably ‘sound’ like 1200W to novice buyers in any case.

What buyers are really paying for when they ante up for this amplifier is Sony’s legendary dependability, and given its flawless performance during my auditions I can safely say that the XM-GTR4A lives up to its name. If you’re shopping for a 4-channel amplifier around the $400 mark and need it to power a set of full range speakers (or two) plus a subwoofer the XM-GTR4A is a great choice. Indeed, it’s going to play noticeably louder than its rivals, and to the type of buyers Sony’s aiming the XM-GTR4A at, this matters more than anything else.