QSC Audio PLD4.5
by Danny Rosenbaum
I'll admit: sometimes it's hard to get excited about power amplifiers. If they do their job correctly, they make signal louder without creating a lot of mess or fuss. But if they do their job poorly, somebody doesn't get called back for the next gig.
In fact, we really only tend to notice power amps when they're doing something wrong. When they clip or thermal, the result can be a jarring reminder of how bad things can be. Sometimes the evidence of an amplifier's bad behavior can be quite dramatic. Square waves at the front end will eventually cause a fire at the back end. (Time to pull out the marshmallows!)
Of course, I can't remember a QSC amplifier ever leaving me stranded, so when I received the opportunity to check out one of the new PLD Series models – specifically, the PLD4.5, the most powerful model in the family – I jumped at it.
All PLD Series models for portable/live sound (and CXD Series for installed sound) are available in a 2RU configuration with four channels, with independent DSP for every channel and a preset wizard that streamlines the setup process. DSP includes crossover filters, parametric EQ, alignment delay and other dynamics processing, and when paired with QSC loudspeakers, proprietary Intrinsic Correction processing techniques help optimize sonic performance. This is the kind of amp that can replace several pieces of gear in your rack.
USB interfaces on the rear panels allow firmware updates as well as the ability to upload loudspeaker tunings and configurations and transfer data between amplifiers. Multiple DSP-controlled power saving modes combined with the class D design increase efficiency, lower weight, and save money.
The most significant aspect of the platform, however, is Flexible Amplifier Summing Technology (FAST), developed to improve power allocation by actively distributing total amplifier power across one, two, three or all four outputs, enabling channels to be combined for maximum current or voltage output, with the largest models capable of up to 5,000 watts continuous (8,000 watts burst power). This was the aspect about PLD that most captured my attention.
Pulling the PLD4.5 out of the box at the shop, my first thought was construction quality. Hefty metal, solid build, and the overall feel of a piece that won't let you down at very high SPL. A surprising thing was finding that the 8,000 watts of (burst) power it could deliver tipped the scales at a mere 22 pounds. (My road crew is going to be happy about this.)
The menu structure was easy to get around and revealed some of the real power under the hood. Equalization, limiting, filters and delays can be recalled via presets that provide the ability to set your sound system parameters at the turn of a knob. The LED display gave me metering and key info, as well as access to all of the programming functions. I could read the display in all types of lighting and from any angle.
Setting up the amp for a gig is quick and simple. Mute buttons for each channel as well as input gain and output attenuation make it easy to maximize gain staging. It also sounds great, with exceptionally solid low-end performance even at high output.
I wasn't surprised to see lots of processing presets for QSC loudspeakers built into the PLD4.5. What did surprise me, however, were all of the presets for other brands. This is an amp that's comfortable making a pair of bi-amp JBL cabinets go to "11" on a live music gig and then driving four QSC ADS12Ts covering a political convention the next. It's a really flexible amp.
It was also great to find that I could do everything needed via the front panel. Sometimes you need to tweak a parameter without hooking up a laptop, and that ability is really appreciated here. The user interface is driven by turning the data knob and pushing an enter button. So if you can run an iPod, you can run this amp.
The most impressive aspect of the PLD is the ability to completely reconfigure the four amplifier channels. They can be split or combined in whatever format meets the particular needs of the day. If you need to drive four full-range side fills, you can use all of them as individual channels. If the next day you're in front of a subwoofer that needs piles of power, combine all four channels to push a single output of up to 7,500 watts – all the way down to 1 ohm.
Three channels to push a sub and a single channel for the HF? No problem. Need to push two biamp cabinets the next day? Again, no problem. It's hard to imagine a gig that would present a problem that this amp won't solve. It's the kind of flexibility that makes it a must-have for busy production companies.
There are 20 factory presets that primarily go through the different possible system variations. The front panel clearly shows these structures by color coding the channels to indicate if you have them set up for LF, HF or full range. Note that recalling the presets does take about three seconds, and the outputs are muted as you do this in order to keep the amp from outputting any strange noises.
Once the amp is dialed-in for the specific needs of a given show, there are 50 user preset slots available for storing these settings. If the capacity to store more than 50 is required, the free Amplifier Navigator software facilitates the storing and managing of an unlimited number of presets.
Times Have Changed
The back panel is also well-equipped, with four XLR inputs with pass-through's to go to another amp as well as a USB port for preset management. Outputs are six Neutrik connectors – two for bridged outputs and four for individual outputs to make connecting to loudspeakers in any configuration simple.
Even the standard IEC power cord is a locking version to add a little bit of security. It's also worth noting that this is a 15-amp cable, probably due to the fact that these amps feature power factor correction (PFC), so the whole multichannel amp, processing, and reconfigurable structure runs off of a single 15-amp circuit. That's a pretty impressive use of technology.
It used to be that four channels of amplification and processing would tie up eight or ten spaces in my road rack and easily weigh more than 100 pounds. Now I can have all of it in two rack spaces weighing 22 pounds. That's the kind of improvement that makes a big difference for sound techs, engineers and sound companies alike.
U.S. MSRP: PLD4.5 - $2,929.99; PLD4.3 - $2,329.99; PLD4.2 - $1,729.99
BIO: Danny Rosenbaum serves as a vice president for Morris Light & Sound, a leading touring company based in Nashville.