Originally published on Andrew-Robinson-Online.com
-----

Introduction

What is an amplifier really? For many, both audiophiles and home theater enthusiasts alike, an amplifier is the heart, and in some instances, the soul of any system. The human heart is a good metaphor for the modern power amplifier, for like the heart, an amp ďpumpsĒ your systemís lifeblood to your loudspeakers. Without an amplifier there would be no sound. But does this make all amplifiers the same? No, not by a long shot. Amplifiers come in a variety of shapes, sizes, channel configurations and power outputs. Within each of those categories there seem to rest a dozen more sub categories and so it goes. When it comes to home theater, the most commonly seen amplifiers are ones often referred to as multi-channel, or amplifiers that are capable of driving multiple loudspeakers at once -typically 5 or 7. The Sherbourn PA 7-350 (7-350 ) reviewed here is of the seven channel variety meaning it can power up to 7 loudspeakers at once in a surround sound environment or setup.

Itís not that the 7-350 is the only 7-channel amplifier in existence -it isnít -but among its peers itís two things; first the 7-350 is one of the more powerful 7-channel amplifiers youíll find and two, itís relatively affordable given said power. But Iím getting a bit ahead of myself. For starters, the 7-350 is Sherbournís current flagship, multi-channel amplifier. Sherbourn, for those of you who may be unaware, is the custom install friendly lineup of products produced by Jade Design -the parent company of Emotiva. Sherbourn started off in life as its own brand before being purchased by Jade Design a few years ago. Under Jade Design, Sherbourn has remained a CI staple, though its sales methodology has shifted away from traditional brick and mortar to Internet direct sales -a la Emotiva. Itís not that Sherbourn isnít still available to installers and dealers the world over -it is -itís just also available to consumers too, albeit direct. Because Sherbournís products are sold direct via the Internet their prices are a bit more advantageous than some of its direct competition. With regards to the 7-350, it retails for $2,519, which includes shipping as well as a full, 10-year factory warranty (5-year transferable) . The 7-350 also comes with a 30-day, in-home trial period at the end of which, if youíre not completely satisfied, you can return the amp to Sherbourn for a full refund.

What you get in the 7-350 for a hair over $2,500 is rather impressive. From the outside, the amplifier itself is rather imposing, measuring 17 inches wide by nearly 10 inches tall and 19 inches deep. It also weighs a ďmetric tonĒ at 99 pounds out of the box. Like all Sherbourn products, the 7-350 comes with the requisite rack mounting hardware as standard, which is good for most AV rack shelves are not rated to support such weight. From the outside the 7-350 is basic but still beautiful. Its smooth black finish is accented by subtly sculpted lines that run horizontally along the bottom edge of the ampís facade. Within this horizontal band and positioned off to the left (when looking at the amp itself) youíll see the ampís polished silver standby button flanked by seven small LED lights. The LED lights are the ampís indicator lights that glow amber when in standby and blue when in use. The top of the 7-350 is dominated by vents that help keep the amplifierís internals cool and should be left clear of any obstructions, this includes other equipment, when the 7-350 is in use. Around back youíll find the ampís input and output options, all of which are thoughtfully laid out with tons of space between each in order to facilitate proper cable management.



Looking at the back of the 7-350 and moving from left to right, top to bottom, the first thing youíll come across is the ampís seven unbalanced inputs. Below each unbalanced input rests a small toggle switch that allows you to select between the 7-350′s RCA style inputs (unbalanced) and its balanced or XLR-style inputs. Again, all seven channels are clearly labeled and spaced out appropriately to accommodate all types of cable be it balanced or unbalanced. Across the bottom, each amplifier channel possesses two sets of five-way binding posts. Why two sets (four) and not a single pair? The 7-350 has two sets of binding posts per channel to better facilitate bi-wiring. If your speakers donít have two sets of binding posts or you simply donít care about bi-wiring, donít stress, for both sets of binding posts run in parallel meaning you can easily just use one and not the other and be just fine. Along the far right side of the 7-350′s back panel there are two trigger input/outputs, a switch to defeat the front mounted LED indicator lights , a master on/off switch and the amplifierís 20-Amp power cord receptacle. That is right, the 7-350 requires a 20-Amp power cord, which also means it must be plugged into a 20-Amp outlet -more on that later.

Specifications

The 7-350 is a fully discrete, dual differential, high current Class A/B amplifier that utilizes a SoftSwitch Optimized, Class-H power supply inside. Now, there is much to do over an amplifierís Class among enthusiasts. Audiophiles tend to like Class A designs, whereas most home theater amplifiers utilize a Class A/B methodology. In recent years Class D has come into vogue. Class H isnít ďnewĒ though admittedly itís not as prevalent as the before mentioned options. While Class H is different, itís not wholly unlike A/B -itís just a little more efficient. At the end of the day, a properly implemented A/B and H design shouldnít sound too different from one another, so donít get hung up on the 7-350 or any amplifierís Class designation. That being said, the 7-350 possesses a 3.3kVA toroidal power transformer inside with 180,000 uF storage capacitance. What is more important is the 7-350′s stated power output, which in this case is a healthy 350 Watts per channel into 8 Ohms and 550 Watts per channel into 4 Ohms. Thatís a lot of horsepower, and for some it might seem like too much.

There is a misconception that if a speakerís maximum power handling rating is said to be say 100 Watts, then your amplifier should not exceed that rating. This is a myth. That figure of say 100 Watts means that for sustained periods that is all the power the speaker can handle. The truth is, music and/or movies, are not constants, meaning they donít play one note at one volume for an indefinite period of time -unless of course your name is Kenny G. Because the music and/or soundtrack changes so does its need for power. At any given point your amp, in this instance the 7-350, could be churning out 10 to 30 Watts -a far cry from your speakerís 100 Watt max. If most of the time the amp is only producing 10-30 Watts (just an example) why then do you need 350 Watts? Itís called headroom. Like a super charger to a car engine, the copious amount of power on tap is there to safely drive your speakers to their limit and thus recreate the full scale of the music or cinema event without distortion or damage being done to you speakers or your ears. You see power doesnít ďcookĒ speakers, distortion or ďbad powerĒ does.

With regards to the 7-350′s distortion, it is incredibly low -less than .02 percent. Signal to noise is reported to be 76dB at 1 Watt (A-weighted) and 100dB at rated power (again A-weighted). The 7-350′s reported frequency response is 20Hz to 80kHz (+/- 2dB). Input sensitivity is rated at 1.7 Volts and gain at 32dB.

Application

The 7-350 arrived hot on the heels of my review of Parasoundís Halo A 21 amplifier. I had been running two Parasound Halo amplifiers, the two channel A 21 and three channel A 31, prior to the 7-350′s arrival. Obviously, the 7-350 allowed me to employ a single amp rather than result to using two, though using two amplifiers or sometimes more isnít uncommon in multi-channel or home theater setups. Does employing a single, 7-channel amp simplify things? Yes, but do you need to rely on an all-in-one solution? No. The 7-350 comes with the requisite hardware to facilitate rack mounting out of the box, which is a good thing. I un-installed my two Parasound Halo amplifiers and inserted the 7-350, with its included rack ears attached, into my Sanus equipment rack. I suggest having a friend or two help you with this as the 7-350 is quite heavy and can be very unruly should you try and mount it yourself.

Once mounted inside my rack using the bottom four spaces I made sure to allow for plenty of ventilation by keeping the next five or so rack spaces above the 7-350 free of any and all equipment and/or obstructions. This meant using a couple of rack blanks to keep things looking neat and tidy. Once installed I connected the 7-350 to a variety of AV preamps beginning with my Integra DHC 80.2, Sherbournís PA-7030 ($1,619) and Emotivaís UMC-200 ($599). Each preamp worked nicely with the 7-350, though for the bulk of this review I opted for the Sherbourn PA-7030 and then later the UMC-200.

I connected the 7-350 to the PA-7030 via balanced interconnects from Monoprice. I only have a 5.1 channel setup so two of the 7-350′s channels sat unused for the bulk of my review period, though at one point I did bi-amp my front left and right mains to positive results. Speaking of my speakers, I utilized my reference Bowers & Wilkins CT 8.2 LCR speakers, that I connected to the 7-350 via custom lengths of 12-gauge speaker cable from Binary, a SnapAV company. For source components I used my trusty Dune-HD Max media player, Pioneer Eliteís BDP-62FD universal disc player and a Roku 2 XS media streamer. The whole setup was controlled via a custom remote programmed in iRule. For video I relied on my reference LED based front projector, SIM2′s M.150. It should be noted that my front three speakers sit behind a 120-inch, acoustically transparent screen from Elite Screensí EPV line of Lunette screens.

Before I go any further I should also note that because the 7-350 requires a dedicated 20-Amp circuit complete with a 20-Amp outlet I had to call an electrician to have one installed in my home. I actually had two installed as more and more high-powered amplifiers are starting to require such connection options. Needless to say, the cost of adding a true 20-Amp circuit to oneís home should be factored into the 7-350′s true cost of ownership, though the cost of having a 20-Amp circuit installed neednít be too expensive. My two 20-Amp circuits cost me under $200 total and were able to be installed in less than 2 hours.

READ THE REST