Marantz MM7055 5-Channel Power Amplifier Hands On Preview

At first blush, the Marantz MM7055 may not seem like a terribly interesting product. Its $1,199 price tag doesn’t appear terribly competitive with Internet-direct products from companies like Emotiva and Outlaw. Moreover, in the age of immersive audio (i.e. Atmos, DTS-X, and Auro-3D), a 5-channel power amplifier seems just a tad quaint. On the other hand, one has to wonder just how far A/V receiver manufacturers can push the envelope. With some models boasting as many as 11 channels of amplification, in addition to the extra processing power required by these formats, it stands to reason that something has to give. Usually, that means they skimp on the power sections of the receiver’s amplifier. A separate amplifier like the MM7055 can give such receivers a healthy boost of power on the main ear level channels where it’s needed most. So what about the question of value? Keep reading to see my thoughts…

At A Glance

Being a Class AB linear multi-channel amplifier, the MM7055 is a relatively simple product. It’s rated to deliver 140W into an 8 ohm load with any two 2 channels driven (20Hz - 20kHz, 0.08% THD), or 170W into a 6 ohm load. Curiously, no 4 ohm specification is provided, but Marantz does claim that the MM7055 is capable of long-term power delivery into low impedance speakers. If that doesn’t sound like a boatload of power, be assured that 140W into 8 ohms is quite adequate to drive almost any speaker to very high levels. More to the point, doubling that to 280W only adds 3dB of extra output, presuming that the speakers are up to the task of dealing with that kind of power in a linear fashion.

On the front face, the MM7055 features an On/Standby button, the iconic Marantz porthole, a protect mode indicator, and a button to turn off the display. The rear panel boasts both RCA and balanced XLR inputs, which is switchable on a per-channel basis. In addition, the MM7055 features a DC trigger input / output, and RC-5 remote control jacks.

Marantz MM7055 Rear Panel

Build Quality

Upon unboxing the Marantz MM7055, I gave it a visual and hands-on inspection. The chassis feels quite solid, as one should expect from an amplifier in this price range. The unit itself weighs in at roughly 35 pounds, so it’s quite a bit heftier than your average “100W x 7” A/V receiver, but it’s not a back-breaker either. The input jacks feel reasonably secure, so you’re unlikely to pull one out with a tight gripping interconnect. However, one nit-pick I have is that the binding posts, while looking nice, are a bit chintzy for a product in this class. They’re essentially dressed up versions of what you’d find on an inexpensive A/V receiver: wobbly, and not well suited for accepting large gauge bare wire (I’d recommend banana plugs for anything larger than 14AWG cable). On the up side, the posts are well spaced, and the chassis itself has a layer of plastic around the binding posts to prevent a stray strand of wire from contacting the metal chassis. Aesthetically speaking, the unit is unabashedly a Marantz. In my humble opinion, the MM7055 is quite a bit easier on the eyes than the comparably priced, plain-Jane Outlaw 7125 I have on hand, but as they say, your mileage may vary.

Glancing through the top cover to check out the guts of the MM7055, a few things stick out. First and foremost, the unit boasts a relatively large EI transformer, which undoubtedly contributes a great deal to the unit’s weight. The other thing that’s immediately eye-catching is the pair of massive capacitors gracing this amplifier. Each capacitor is rated at 33,000uF / 71V, which ensures plenty of reserve capacity for dynamic peaks. To see how this compares to a high quality receiver, one can look to the Audioholics review of the Marantz SR6004. That unit boasted a pair of 10,000uF / 63V capacitors, which offer less than a quarter of the energy storage of the MM7055’s caps.

Guts of the Marantz MM7055 Amplifier

The final item of note in my inspection is Marantz’s “thermal tunnel,” upon which the amplifier’s output devices are affixed. It consists of an aluminum tube with a fan on one end, and an exhaust to the exterior of the chassis on the other. The practical effect of this is to reduce the weight of the amplifier, since active cooling reduces the need for large, heavy heat sinks. My back thanks Marantz for going this route, versus adding another 5-10 pounds’ worth of aluminum to the mix.  It is likely that Marantz didn't certify this as a 4-ohm product because it would have required even further heat reducing measures to do so which adds cost and weight.

So How Does It Sound?

Obviously, the million dollar question is this: how does the Marantz MM7055 stack up in real world use? Simply connecting the amplifier to my system and turning it on, I observed that the MM7055 was devoid of audible transformer hum as well as hiss through my speakers.  This contrasts with my Outlaw Model 7125, which does exhibit a good deal of hum from its heavy duty 1,600VA transformer, as well as a bit of hiss from the speakers. While neither are serious problems at moderate to high volumes, I found these factors did make a significant difference in low-level listening.

In terms of basic response through my speakers, both the Outlaw and the Marantz sounded and measured identically. No surprise there, since both amplifiers appear to be of good quality. The big question I had was whether or not the Marantz had the guts to drive my speakers up to the volumes I desire. In my case, this is no small task. While my room isn’t huge (<3,000 cubic feet), none of my speakers (L/R KEF R500, C: KEF R200c, Surround L/R: KEF Q800ds) are especially efficient; all dip down to the 4 ohm range or slightly below; and I do occasionally let things rip at full reference level. Suffice it to say that the MM7055 didn’t have any problems meeting my expectations. Running Jurassic Park and Star Wars: The Force Awakens at -5dB from reference (with occasional jumps to full reference), the Marantz delivered everything that was asked from it, while not getting more than moderately warm to the touch. Pretty cool.

Conclusion

If you’re in the market for 5 channels of high quality amplification, the Marantz MM7055 might be just the ticket. At a price that won’t require you to sell a kidney, one gets a quiet, attractive, amplifier that won’t give you a hernia when you place it in your equipment rack. From my time with it, I can also attest that it has plenty of real world power, even when driving speakers with impedance dips into the 3-4 ohm range. While the MM7055 may not be the best bang for the buck around, I do feel that it presents a compelling value to audiophiles who look at more than just rated power when buying an amplifier. Of course if you already own a Marantz Dolby Atmos AV Processor (ie. AV8802A or AV7702mkii), the MM7055 amplifier is a perfect aesthetic match that

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.