|Sunfire Theater Grand 7400 Multi-channel Amplifier|
|Home Theater Power Amplifiers Multi-Channel Amplifiers|
|Written by Ken Taraszka, MD|
|Thursday, 01 February 2007|
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Grown men have spent their entire lives fighting and even dying for it. We often associate power with size and weight, but can be fooled by the little guy whose abilities can drop the largest of men. Bob Carver is known for packing amazing amounts of power into the smallest and lightest of boxes with his amplifiers, and it seems Mr. Carver has empowered yet another “little guy” with his new Theater Grand Amplifier 7400. As president of Sunfire, Bob Carver has been a major player in the audio industry since 1970, when he founded Phase Linear, and he has kept pace with the rapidly changing business throughout the years. His advances in amplifier technology are legendary and his new top of the line seven-channel amplifier, the Sunfire Theater Grand Amplifier 7400, puts out a rated 400 watts per channel into eight ohms into all seven channels, and doubles down to 1600 watts per channel into two ohms for peaks. It offers two different output impedances for the front channels, both balanced and single-ended inputs with the ability to daisy chain multiple channels together for bi- and even tri-amping your speakers, and multiple options for powering up the amp. All this comes at a price of just $4,449.
When the new TGA 7400 arrived, I quickly unpacked it from its box and high-density foam and carefully unwrapped it to reveal the new look Sunfire has bestowed upon its components. Gone are the rounded edges of the previous models; they have been replaced with a milled aluminum faceplate and steel case. The side edges of the faceplate curve in slightly, giving the faceplate the look of being curved as well. The front of the amp is otherwise pretty sparse, exhibiting only a small power button in the upper left side with an LED above it. The rear is far more complex. On the right side are nine sets of binding posts for the front left and right speakers. This amp offers two types of outputs for these speakers, current source and voltage source, with one associated fuse for each of these channels current source options, and five sets of binding posts for the remaining channels. The IEC plug for the removable power cord is located in the bottom right. Seven sets of inputs are on the left, each offering two single-ended and one balanced input. On the far left side are the 12-volt triggers and an auto on/off switch that allows you to choose how to activate the amp, either keeping it on at all times or allowing it to be turned on either by the 12-volt triggers or whenever an audio signal is present on any of the channels. All the speaker binding posts are gold-plated and accept spades, bananas and bare wire. Threaded 12mm gold-plated nuts bind your choice of terminals to the posts. The amplifier measures just 17 inches wide, 5.9 inches tall and 16.7 inches deep and weighs only 40 pounds. Sunfire is able to pack so much punch into such a small and light amplifier in great part due to the use of their Tracking Downconverter™ technology, which provides high current power on an as-needed basis that greatly minimizes heat production, and therefore the need for heat sinks or a fan to maintain proper operating temperature.
I connected this amp to my Canton Vento speakers with Transparent Reference cables and to my reference home theater gear, the Meridian 861v4 preamp processor, Meridian G98 DH player, Teac Esoteric DV-50s and Toshiba HD-XA1 HD DVD player, for evaluation. Power was fed to the amp via its own dedicated 20-amp circuit, run through a Chang Lightspeed CLS 9900 Amp power conditioner. Due to some changes in my main system’s wiring, I had to relocate the amp to the front of the room, and I had not gotten around to having the electrician move one of my dedicated 20-amp lines to that part of the theater. When I first plugged in and powered up this amp on the line that also does the fans and lights for the room, the lights dimmed for nearly two seconds. I immediately switched over to one of my dedicated lines with a longer cord, as this amp was obviously going to need some good power to perform at its best and my room still has a few power demons haunting it.
Multi-channel amplifiers tend to get pretty crowded on the back plate, and this is no exception to that rule. Packing nine sets of binding posts and seven sets of inputs leaves little free space. The fact that the binding posts have 12-millimeter nuts to tightly compress the wire terminals was a big help here. These allowed me to secure the position of my wires so that they stayed put. While it took some finesse and a little planning, I was able to easily connect all my speaker wires to the amp. Had I used wires with very large terminations, this might not have been the case. Low-level inputs were connected via the balanced inputs initially. Then, in order to use four channels of this amp to bi-amp my front speakers with both current and voltage source, I used the RCA inputs.
The Sunfire TGA 7400 offers two different outputs for the front speakers, current source and voltage source. Current source is the output method most frequently associated with tube amplifiers, while voltage source is most often associated with solid-state amplification. The inclusion of these two different outputs allows you to tailor the sound for the main speakers several ways. You can obviously use either one or the other, or bi-amp or bi-wire them using both. You could even bi-amp then with four channels of voltage source output. I initially connected the front speakers to the voltage source outputs, and then switched to the current source. For bi-wiring, Sunfire recommends using the voltage source for the bass and current source for the highs. I tried this set-up, as well as bi-amping my Canton’s with four amplifier channels. After making all the necessary connections, I set the auto/on/off switch to “on,” enabling the signal sensing option for automatically turning on the amp, and let the entire set-up burn in for a little over 100 hours before doing any critical listening. The initial set-up took me several hours, as I had to rewire and relocate numerous components in my home theater. Had I just needed to switch out the amps, I could have been done in 15 or 20 minutes – it was quite simple.