Amplifier - Import Tuner Magazine

Here's an amplifier that offers loads of power-we're talking bulk, economy, warehouse club power here! The price looks good and it's supposed to be an efficient Class D design, so let's take a look at what this much power will really cost you.

The Opti2000D is a discrete class D mono-block amplifier rated to make 700 watts RMS at 4ohm, 1100 watts RMS at 2ohms and 2000 watts Max at 11/42ohm. Total harmonic distortion (THD) is given as 0.1% at 1 watt, 4ohms. Lanzar has included exactly what you need for a huge subwoofer amplifier: a 24dB/octave lowpass crossover and 24dB/octave subsonic filter, phase reverse switch and dash-mounted remote gain control. If 2kW won't do the job you can strap two of these monsters together for an advertised max power of 4000-watts!

From the very first look at this beast you know it's an amplifier. The 19" x 10" x 2.5" extrusion is asymmetrically stylized with rounded edges, lightly grained and bright aluminum in color with a diamond cut 3D Lanzar logo and a black strip with the ID badges along one side of the top. RCAs and controls reside on one color-matched steel endplate while the power and speaker connections and six fuse holders fill up the opposite endplate. The bottom plate is also stamped steel, with louvers for airflow near the transformers, and mounting holes where the plate extends beyond the endplates.

The control endplate includes a Slave/Master switch and a Data Link port to strap a pair of Opti2000Ds across a single load.

Circuit DesignAlthough the Opti2000D is over 19" long, it is really packed full. The first thing you notice when you pull the cover off is the number of transformers and inductors spread throughout. There are two large power supply transformers with a dual secondary inductor, four small B+ filter inductors and two medium output filter inductors. The second surprise is the array of "hang off" devices - the transistors and rectifiers that hang off the sides of the main PCB so they can be clamped to the heatsink. It looks more like an A/B amp than a D, as class D generally uses a single pair of large output devices per channel. This one uses seven pairs-more on that later.

The power supply and output circuitry occupy approximately 16 inches of the 19-in amp, with the signal circuitry squeezed into an L shape at the end of the main pcb. There is very little separation between the signal and the output traces. This amp uses discrete class D drive circuitry on a vertical module rather than the more common class D configuration. There is a small vertically mounted fan between the module and the output inductors, but no shrouds or vents to define the airflow. The fan seems entirely useless to me, but even on my test bench I could not get this amp nearly hot enough to trigger the thermal protection.

Through-hole components are used throughout, even on the class D drive module. The main PCB is double-sided FR-4 with 2-ounce traces reinforced in a couple of places with 10awg jumper wires. Resistors are high-tolerance, and most of the capacitors in the signal path are film-type, all in all pretty high quality parts. Many of the large metal terminal blocks appear to have been problematic to solder in, with very little wicking (drawing of liquid solder through the holes to the top side) and visible "cold" joints. Cold joints are the result of having the solder hot enough to be liquid, but the part that is to be soldered is not hot enough to create a good bond. This is a common problem with large chunks of metal because they require a lot more energy to heat up than the tiny lead of a resistor or capacitor. While I expected this to be a problem on the power and output terminals, there was no evidence of power restriction even while drawing upwards of 125 amps on the bench. The only things that heated up much werthe power cables and speaker wires.

Since this beast is mostly power-supply, let's take a closer look at how it works. The B+ and Ground connect through 4awg set-screw terminal blocks. In turn, the B+ goes directly through a bank of six parallel 30-amp fuses, then through four parallel inductors to clean it up a little and proceeds to a pair of large litz-wound transformers. A single 3525A pwm controller running at 30kHz drives a total of 20 IRFZ44N switchers (5 pair for each transformer) for a total power dissipation of 1,880 watts at 25 degrees C. There are fourteen primary caps at 2200fd each for a total of 30,800fd on the 12volt side. Six 2200fd caps stabilize the 77voltrails, all caps rated at 105 degrees C.

The output section is the interesting part here. Most class D outputs use a single pair of output devices for each channel as I mentioned earlier. The outputs in a class D configuration are required to switch extremely quickly, historically very close to their limits. This switching speed limitation is what has restricted most class Ds to lower frequency ranges. The devices have not been particularly accurate at those high speeds, so it wasn't a good idea to arrange more devices in parallel to increase the power output. The potential for shorted outputs when two devices are not working together properly was too great. Some transistor manufacturers concentrated on higher power single devices, but some have developed more accurate, higher speed devices, which is what Lanzar is using in the Opti2000D to pass 2kW on to your speakers. There are 14 International Rectifier FB31N20D outputs, each capable of 200 watt dissipation at 25 degrees C. That's a total capacity of 2,800 watts, definitely overbuilt here! The output leaves by way of two 8awg terminals-the size of a normal amp's power terminals!

PerformanceThe frequency response measured 15Hz to 130Hz + 1dB. Lanzar shows 15Hz to 150Hz + 3dB, which I verified. There is a distinct hump at 43Hz (probably an artifact of the bass boost circuitry) even with the Bass Boost turned all the way down. Because of the narrow frequency scale of the graph it looks worse than it really is-the peak is less than 0.7dB.

At first glance, I thought the 4awg power connectors were small for a 2kW amp, but the unit proved to be very efficient. In the neighborhood of 80% efficient, the cable gauges are perfect, though I could not draw anywhere near the 180 amps that it is fused for. The amp puts out a lot of power, but seems to do it without breaking a sweat.

Overall the amp measured as advertised, with RMS power meeting Lanzar's spec and then some, though I could not duplicate the Max power at 0.5ohm load. The Crossover and Subsonic Filter were right on the stated ranges with nice clean slopes, although the slopes were closer to 22dB/octave than 24dB as stated. The amp was pretty noisy on the bench but remember, with gain comes noise, and this amp has lots of gain. S/N and Damping Factor measured lower than spec (see specifications).

The crossover measured 22dB/octave, from 48 to 155Hz, close to Lanzar's specs of 24dB/octave, 50 to 150Hz. The subsonic filter measured 22dB/octave, 14 to 56Hz-a little off of Lanzar's specs of 24dB/octave, 15 to 40Hz. Like the crossover, the bass boost was pretty close to spec with a maximum of +19dB boost at 43Hz. Both the short circuit and overload protection worked well; the amp recovers automatically from a brief short-circuit, but extended short circuits (5 seconds or more) require turning the amp off and back on to reset. I could not heat this amplifier sufficiently to trigger the thermal protection, and believe me I tried. Hey, efficiency is your friend.

There was no turn-on noise, but the amp puts out enough noise to tell when it is on, even with the gain turned down. Turn-off consistently generated a sharp pop.

Owner's ManualThe owner's manual was not written with the novice in mind. Installation instructions are definitely for installers that already know what they're doing, using phrases like "Make sure there is sufficient air flow around the intended mounting location" and "further fine tuning of the various controls may be necessary to obtain the desired results." There is no mention at all of connecting the speaker wires in this section. The diagrams and pictures are good, clearly showing connections and how to bridge two amplifiers to a single speaker, but again the manual fails to explain the main features and how to correctly set them. The amplifier carries a three-year warranty.

Listening TestI cruelly subjected the LSE's electrical system and subwoofer to the brutality of the Opti2000D. I put in a new battery six months ago, and it's been wired with 4awg cable, so what the heck. There was no engine noise, just some amplifier noise that you couldn't hear when the trunk was closed. The irritating turn-off pop was still present. The main problem with this listening test was that the rest of the system couldn't keep up with the DVC 12 inch with this much power. At lower listening levels, this much power kept the 12 inch quick and tight, and it reproduced the lowest frequencies I could send to it. Planet Krypton from the old Car Audio Nationals CD goes down below 20Hz, and it just kept shaking. Had I been driving I would have thought there was something wrong with the car. I went through my usual array of CDs with good results without any Bass Boost help from the amplifier. I put in the "sine bombs" (basic rhythms with descending sine wave sweeps) and cranked the bass boost all the way up. With the boost up, I had to turn the level down and lost some of the lower frequencies, so I turned the boost back down and cranked the gain back up where it was before. I couldn't hear much from the mids and highs, as they are running a mere 150 watts each, but I cranked it up until I thought things were starting to come apart. (Ahh, the good old days.) The amp was barely above room temperature after 20 minutes of fun.

ConclusionThe Lanzar OPTI2000D does what it is supposed to do; that is, send lots of power to your subs. It is one of the most efficient amplifiers I have tested and appears to be pretty bulletproof. It pays to buy in bulk too-1,962 watts measured at a price of $722.19, that's about 37cents per watt! At a price like that you can put up with a little noise in your subs, and your friends can help you hook it up.