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Sony Xplod XM-ZZR3301
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Sony has always been a leader in high-value car audio products. This time we are going to have a look at one of their top-selling Xplod Series Class-D monoblock subwoofer amplifiers, the XM-ZZR3301. Rated at 330 watts into 4 ohms, and 600 watts into 2 ohms, the Sony XM-ZZR3301 sells for only $199.95, making it one of the best “watt per dollar” deals available!


The Sony Xplod XM-ZZR3301 amplifier, moderately sized measures about 14” x 11” x 2.25”. Stepping away from the traditional rectangular shape, the amplifier brings a bit of style to the mix with the ends of the amplifier being somewhat V shaped, and the upper surface of the cast aluminum heatsink offering some molded-in-design elements that add a touch of class and uniqueness. In the middle of the top of the amp is a large illuminated bar which lights up in a bright blue color when the amp’s turned on. All the connections and controls are along one side for ease of installation and adjustment. The connections for power and speakers are made via gold plated Phillips-head screw terminals. The power terminals will accept ring terminals that can be used with 4 or 8 gauge wire, and the amp is fused with
a pair of 30A ATC style fuses.

Four speaker terminals (although it’s a single channel, additional terminals are provided to aid in the parallel connection of woofers) will accept 10 gauge bare cable or 8 gauge with the appropriate ring terminals.

High level inputs are also provided if you want to provide signal to the amp from an existing amp or head unit speaker outputs, and these can be used as signal sensing inputs to turn the amp on when no dedicated 12 volt trigger is available. The high level inputs will accommodate amplifier power levels over 100 watts.

Control and adjustment features include what you’d expect; pots for gain, 6Hz-70Hz subsonic filter, +10dB of bass boost, and a 50Hz-300Hz crossover frequency adjustment.

XM-ZZR3301_angled_optIn the interest of long term reliability, there are three different protection modes built into the Sony XM-ZZR3301, a thermal protection circuit first rolls back the power output as heat builds, allowing the music to continue, and a second mode eventually turns the amp off if the temperature becomes too high. Additionally, a short circuit protection mode engages if the speaker wires become shorted to each other or to ground. I also found another protection mode quite by accident during my listening…read on.


A peek inside the XM-ZZR3301 revealed a basic but well
constructed Class-D design. The double sided PCB places all the small signal surface mount parts, like the control IC’s, op-amps, and associated circuitry on one side of the board, and all the larger through-hole parts on the opposite side. This method allows the overall PCB to be made smaller without sacrificing area for copper traces. And it has plenty of copper for high current demands, and a heavy copper buss bar is used to augment current delivery to the power supply devices. The power supply itself is relatively robust, using a good quality toroid, and 6600?F of capacitance. The power supply switching devices are made up of six TO220 size Fuji MOSFET’s and are easily capable of handling the maximum current demand of the amp.

On the output side of things, the output devices are four N-Channel Fuji MOSFET’s and current is supplied via a total of 7000?F of capacitance. There is a large second order output filter to remove the Class-D switching hash from the audio. Overall, the design is clean and very well made.

Read on for Results


Of course I had to give it a listen before I made any measurements of my own, so after getting the Sony XM-ZZR3301 connected in my reference system, I set the crossover for about 80Hz, and using
a 2 ohm woofer load, began my listening portion of the evaluation. From a sonic standpoint, the Sony Xplod XM-ZZR3301 sounds fine.
I could not fault the sonics at all... It’s everything a Class-D amp should be! The XM-ZZR3301 provided plenty of power for my woofer, and easily got the volume to higher levels than I cared to listen at. The controls worked fine, and I really liked having the ability to dial the subsonic filter down low enough so as to basically remove its effect. This is important when using a sealed enclosure design, as you really don’t need the amp to be filtering out the really low stuff, because that’s one of the reasons we build sealed enclosures!

However, I do have a couple of minor gripes with the Sony XM-ZZR3301’s performance. First, the amplifier has a distinct “pop” sound every time I turned it off. This is a pet peeve of mine, and while I’m told most people could care less, it drives me nuts. The second issue was found almost by accident. As I was listening to the amp, my phone rang. Without reducing the volume, I simply paused the CD, and took the call. When I returned to listening, the instant I hit the play button, the amp went into protection. I turned it off, and it reset immediately, but after a couple of go-rounds, I learned the Sony XM-ZZR3301 does not like to be asked to go from zero output to fairly high output levels instantly. It needs the signal to be introduced on a bit more gradual level, or it might snap into protection mode.

Now, this isn’t necessarily the kiss of death, because most of us probably won’t want our system to go from zero to LOUD in an instant anyways. But if you pause your music while listening at high levels, and then try to resume at high levels, you could experience this particular idiosyncrasy. It also makes the amp a poor choice for “burp style” SPL contesting, if that is any consideration.

On the Bench

Moving the Sony amp from the listening room to the electronics lab, I was pleased to note that the XM-ZZR3301 exceeded its published CEA-2006 specifications for power and signal to noise! Other measurements all came out good as well! The response curve is flat and wide, and the bass boost, subsonic and crossover filters work exactly as intended. Efficiency was also very good with numbers approaching 90% with a 4 ohm load. The amp has very low THD+N at 1 watt for a Class-D design, which is a tribute to the attention to detail in the amplifiers layout and component selection.

1 Max Flat-Frequency R_opt 2 Crossover Range-Freq_opt
3 Subsonic Filter-Freq_opt 4 Bass Boost-Frequency_opt


The Sony XM-ZZR3301 is a very good amplifier for very little money. There are very few amplifiers available that can deliver this much real power for under 200 bucks. If you are on a tight budget and like it loud, here’s your amp. It sounds good, and it’s well made to be a reliable piece of gear. I’m fussy and a bit of a nit-picker when it comes to pop noise, and I’m not keen on the over-zealous protection circuits. But if the turn-off pop is no big deal to you, and if you either won’t encounter, or simply don’t mind the operation of the protection scheme needing an occasional reset, it’s a very good choice and a great deal.