When choosing a power amplifier there are a number of important factors you have to consider depending on the application. If you need an amplifier to power a PA in a live situation then the maximum rated output could be close to the top of your list. Another popular application for a power amplifier is in the studio, and without doubt a major deciding factor here is the accurate reproduction of the original signal. In both cases reliability and value for money weigh in heavily so with all these factors in mind lets take a look at Mackie's FR series power amplifiers.

For those primarily interested in using an amplifier in a live situation you're going to need an amplifier that sounds great at high volume while producing an absolute minimum of distortion as well as the ability to work well with others, and one of the first features of the FR series which impressed us was the ease in which multiple units can be joined together to power very large PA's (When used in bridge mode each amp is capable of producing as much as 1200 watts.)

Coupled with a rugged exterior and an extremely user friendly rear panel, which includes male and female XLR audio inputs as well as Speakon connectors (MR1400 model) in the output department, the FR series is as close as you're going to get to the perfect PA system power amplifier.

Another consideration when choosing any power amp has to be its ability to keep cool under less than favourable operating conditions, because if it overheats it'll go down. So what Mackie have done is to turn most of the front half of the amp into a cooling tunnel (it's like a smaller quieter version of a NASA wind tunnel. Take a look at the image above and see the horizontal grills where the air is drawn into the chassis). The cool air then washes over the hot amplifier output transistors before being expelled through the sides. Unlike other amplifiers where the fan sucks air in one end and blows it out the other the Mackie design closely manages the air flow offering a surprisingly simple but effective solution to one of the biggest problems a power amplifier will ever face.

If the temperature within the chassis ever exceeds 140°F (60°C) the fan automatically kicks into high-speed mode and the hot LED lights up to let you know. If things get worse and the temperature exceeds 176°F (80°C) the output will be automatically muted, to protect your speakers, the unit will go into standby mode and the protect LED's will light, letting you know what happened. The unit remains in this condition until things cool down. In the extremely unlikely event that a short circuit ever occurs a dedicated LED will inform you.

Don't think these LED's are put there because this stuff happens all the time, far from it. How many times have you ever had to use your seat cushion as a flotation device? Only under extremely punishing conditions will you ever see anything other than the signal present, level metering and cold (normal fan speed) LED's lit.

Temperature problems may not be your biggest concern in a studio setting, but fan noise could be. We were amazed to discover, when turning the unit on for the first time, that the fan was completely silent, only to hear it kick in after the three second delay expired. A lot of people actually prefer passive heat reduction alternatives because of fan noise problems but because the fan in the FR series is buried so deep within the chassis it's hardly noticeable, in fact we have a Macintosh (which is quieter than a PC) running at all times in the studio, so zero problem in the fan noise department.

Something you will be looking for though will be accurate reproduction of the original signal with a minimum of noise, and although all you'll ever need to know about the technical specifications of this amplifier can be found at the base of this page there's nothing like turning it on and listening to it loud.

We chose a play a CD that was produced using nothing but electronic musical instruments (Ye Olde Space Bande by The Moog Cookbook to be exact), and ran the output through our old two-ways complete with their five inch "bass" speakers (we understand you're most likely building your studio from the ground up so wanted to approximate a normal environment, and if you're wondering how an amplifier capable of powering a PA can be used to run our little speakers without blowing them to bits go here and find out about impedances and stuff then come straight back).

At comfortable listening levels, so that the signal LED's on the front barely lit, we immediately noticed a big increase in clarity. It seemed easier to differentiate between various instruments as definition within the stereo field came closer to the way the music was designed to be heard. At increased volumes, when the first couple of LED's lit up, the distortion and added noise we'd got used to with our old amplifier simply wasn't there anymore. It was just........louder. Add a pair of good studio monitors and you'll have yourself a professional quality monitoring system.

Here are a couple of extra features normally found in very expensive power amplifiers:

Built-in subwoofer crossover

Rugged output stage for incredible current output (in excess of 60 amps)

Fully discrete components (instead of integrated circuits)

Built-in low-cut filter and subsonic stabilizer

Sweepable shelving EQ "knee" position (from 2kHz to 6kHz)

Godzilla strength speaker binding posts

Rear rack rails for added support

and last but not least........

A great looking front panel with handles

Technical Specifications (M·1400)

250 watts per channel into 8 ohms from 20Hz to 20kHz,
with no more than 0.012% THD

425 watts per channel into 4 ohms from 20Hz to 20kHz,
with no more than 0.025% THD

630 watts per channel into 2 ohms from 20Hz to 20kHz,
with no more than 0.050% THD

Just in case your still wondering about impedances and stuff there's still time to go here and find out

Bridged mono operation:

850 watts into 8 ohms from 20Hz to 20kHz with no more than 0.025% THD
1260 watts into 4 ohms from 20Hz to 20kHz with no more than 0.050% THD

Maximum Power at 1% THD:

280 watts per channel into 8 ohms
480 watts per channel into 4 ohms
700 watts per channel into 2 ohms
960 watts into 8 ohms bridged
1400 watts into 4 ohms bridged

To contact Mackie Designs check out their entry in our Manufacturers department.

electronicmusic.com/features/reviews/hardware/m1400.html