Most spec sheets suggest “8 ohms or higher” for the bridged-mono configuration, which is the equivalent of loading each channel to 4 ohms. (See Figure 3 for amplifier power equations.)Įxamples include large full-range passive boxes and transformer-distributed (i.e., 70- or 100-volt) loudspeaker systems. This is useful for driving a load that can handle a lot of voltage swing, but whose impedance is high enough to not excessively load the amplifier. The difference is that the power amplifiers are passing audio signals (not DC) and that they are wired to a utility power source (so they don’t get depleted over time like a battery).Ī two-channel amplifier configured for bridged-mono can swing twice the voltage than either channel individually, at the same current as one channel. Let’s substitute power amplifiers for batteries. Which configuration is best? It depends on other factors. So, having two batteries allows me to get more voltage, or more current, than can be supplied by a single battery. There are now a number of multi-channel amplifiers in the professional audio marketplace that support series-parallel connection. That’s a common practice for batteries but not for audio power amplifiers. If you need more voltage and more current, you can connect four power sources in series-parallel. The current flow depends on the load impedance, but the available current is equivalent to that of one of the batteries. Twice the voltage, same current – remember that. The current remains the same as for the single battery. In the series configuration ( Figure 1), the output voltages add, so I now have a 3-volt DC supply. If I have two AA batteries, I can connect them in series or in parallel. Let’s not worry about for how long, which is mAh. Battery AnalogyĪ single AA battery is 1.5 volts DC, and can source about 2000 milliamps (mA), continuous. Let’s cover the basics with a simple example of connecting multiple power sources. These potentially useful configurations are often misunderstood and mis-used. Since we call a two-channel amplifier “stereo,” configuring the channels to combine their outputs into a single load is referred to as “mono.” There are two possibilities – bridged-mono and parallel-mono. But, having two amplifier channels in the same box can provide some other benefits. Even though this is the most popular form factor for professional amplifiers, the majority of sound reinforcement systems aren’t stereo. Two audio channels, two loudspeakers, two amplifiers, two ears – it seems logical. Why two amplifier channels? It’s most likely due to the popularity of stereo playback systems since the early days of hi-fi.
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