Lately I’ve been guilty of taking power amplifiers for granted, and I doubt I’m alone. Current designs are incredibly capable and reliable; provide them with power, signal, and a loudspeaker to drive and they can often be forgotten about until it’s time to load out.
However, in recent years, manufacturers have packed a variety of new features into their power amplifiers, many of which warrant more attention than they’re given. Modern amplifiers offer impressive connectivity, signal processing, and power output, and it’s worth taking a moment to appreciate the options we have at our disposal.
The present state of power amplifiers is the result of decades-long design trends, the most obvious of which is increased power density. Until the early 2000s, a common form factor for high-power touring amplifiers was two channels in three rack spaces. Today, 2U is the norm and it’s common for this smaller chassis to hold four channels rather than two.
For perspective, consider the venerable Crown Macro-Tech 5000VZ. A staple of touring and larger-scale installations a generation ago, it’s rated at 2,000 watts per channel into 4 ohms. The 3U chassis contains two channels and total weight approaches 80 pounds. In contrast, a modern amplifier such as the Dynacord TGX20 supplies 5,000 watts per channel into 4 ohms from a 2U chassis that contains four channels and weighs about 40 pounds. (And that’s not mentioning additional onboard capabilities that include sophisticated DSP, FIR filtering, audio networking and much more.)
Such a massive increase in power density was made possible by the adoption of a different amplifier topology, often referred to as a class. In very early amplifiers, the output devices were forced to conduct for the entire cycle of a waveform; this is referred to as Class A operation, and it is less than 30 percent efficient. Class B amplifiers increased efficiency by allowing half of the output devices to switch off for each half-cycle of a waveform, at the expense of some distortion. Classes A/B, G, and H followed as further refinements to this concept, resulting in roughly double the efficiency of Class A.
Today, the most powerful and efficient amplifiers are Class D, or switching power amplifiers. They use pulse width modulation to express the input signal as varied-length square waves; this allows for tight control over when the output devices conduct, resulting in real-world efficiency beyond 90 percent. Higher efficiency also produces less heat, allowing for the smaller chassis we see on modern touring amplifiers.
Other quality-of-life improvements have accompanied the transition to switching amplification. Because they must dissipate less thermal energy, heat sinks have shrunk, making the units significantly lighter. Modern power supplies are capable of operating on a wide variety of mains voltages and frequencies; due to the variety present throughout the world’s electrical grids, this is an invaluable feature for international touring. In addition to the usual analog inputs, digital I/O options are available as well, most commonly AES and Dante. This makes large and highly distributed systems easier to manage.
With digital I/O comes another important feature: network connectivity. An array of sensors is built into most amplifiers, measuring a variety of useful data which can be reported to a technician at their computer. Quantities such as the input and output levels, mains voltage, temperature, and the impedance across each output can be valuable information when troubleshooting or monitoring a system; network connectivity allows us to view all of this from one convenient location.
Amplifiers have had some amount of signal processing capability for a while now. Basic functions such as main/sub crossover, low frequency protection, and limiting were often found on rear panel switches. For more complicated functions like equalization, delay, and multi-way crossovers filters, we relied on external signal processing equipment between the console and the amplifiers.
Modern amplifiers include robust digital signal processing, making those external devices largely obsolete. Onboard DSP handles input mixing, delay, parametric equalization, crossover filters, and thermal and peak limiting. Thanks to the aforementioned network connectivity, all of this can be controlled from a computer instead of via paging through endless front panel menus.
Loudspeaker manufacturers have taken full advantage of onboard DSP and networking. Loudspeakers (and the amplifiers driving them) are assigned specific DSP presets, helping to ensure more consistent performance while also protecting transducers from being over-driven. End users can’t typically edit or even view the parameters of these presets; however, they usually retain access to important system optimization features like equalization and delay.
Configuration and management of DSP settings takes place in a system control software, where technicians can assign a job to each amplifier channel. It’s also possible to link parameters across multiple channels to gain control over groups or subsystems of loudspeakers.
Amplifiers carrying loudspeaker-specific presets fits into a larger trend of manufacturers creating a closed system for their products to operate within. Gone are the days of setting up crossovers and limiters out in the field; after all, manufacturers have laboratories at their disposal and have better knowledge than we do about what their products can handle.
Dynacord expands the scope of SONICUE
These new additions expand the lineup of loudspeaker options for integration into the powerful SONICUE ecosystem along with Dynacord’s system-wide range of hardware solutions, which includes the flagship IPX and TGX series power amplifiers and the new MXE5 matrix mix engine. This gives consultants the flexibility to use loudspeakers from multiple brands with a single state-of-the-art power and control platform.
The settings are engineered by Dynacord to reproduce the manufacturer settings and field-tested by professionals to verify accuracy. Factory settings for the complete portfolio of Fulcrum Acoustic loudspeaker models are also available, developed in collaboration between Fulcrum Acoustic and Dynacord.
Some companies, such as L-Acoustics, d&b audiotechnik and Martin Audio release their own branded amplifiers for use with their loudspeakers. Further, companies such as Electro-Voice and JBL have corporate relationships with particular amplifier manufacturers, respectively Dynacord and Crown, for which they develop their presets. Companies without these relationships turn to amplifier manufacturers such as Powersoft, QSC, Linea Research, Lab Gruppen and others. Regardless, loudspeaker manufacturers make sure that their products are driven exactly as intended, with DSP and system control integration to thank for that.
Moving forward, we should expect to see many of these trends continue. The remaining efficiency gains in switching power amplifiers are marginal, so continued power density increases are likely to come from decreases in chassis size. As manufacturers more closely intertwine their loudspeakers, amplification, signal processing, and control, onboard DSP will continue to become more capable.
Both of these will be helpful, as modern array processing techniques require an increased number of amplifier channels; low-frequency steering such as Meyer Sound LMBC (Low-Mid Beam Control) would not be possible in arrays with multiple-box circuits. However these future improvements come about, the current state of power amplifiers provides an impressive starting point – we should have quite a bit to look forward to.