While setting up your amp, you might come across switches that allow you to configure the amplifier
in different ways. In order to get the best possible performance and to avoid damaging your
speakers or your amp, it's really important you understand what each mode does. In this video, I'm
going to teach you the difference between stereo mode, parallel mono mode, and bridge mono mode.
But if this is our first time meeting, my name is Kyle. Welcome to Audio University.
There are three modes that you'll often find on multi-channel amps:
stereo, parallel mono, and bridge mono. Let's take a quick look at the differences.
The most common setup is stereo mode. This is the mode you'd use
if you just wanted each channel of the amplifier to operate independently.
In this example of a 2-channel amplifier in stereo mode, input 1 is routed to channel A and
input 2 is routed to channel B. It's the equivalent of using two separate amplifiers.
Parallel mode is similar but slightly different.
You'd use parallel mode if you wanted the same signal to be routed to both amp channels.
In parallel mono mode, input 1 is routed to both channel A and channel B. It's
effectively the same thing as using a Y cable to connect a single source to both inputs.
While the two amplifier channels work separately in both stereo mode and parallel mono, in bridge
mono the two amp channels work together. By harnessing the power of both amplifier channels,
you're able to supply the speaker with more power than either channel could supply alone. In bridge
mono mode, input 1 is routed to both channel A and channel B just like in parallel model mode.
However, bridge mono mode is different in a few very important ways. Firstly, the way you
connect the speakers is usually different in bridge mono mode than it would be in stereo or
parallel mono mode. In both stereo and parallel mono mode, the positive and negative terminals
of each speaker are connected to their own set of amplifier terminals - positive to positive,
negative to negative. Remember - the two amplifier channels are working separately
in both of these modes, even though they might be amplifying the same signal.
However, in bridge mono mode you'll usually connect a speaker between the positive terminals
of the two amplifier channels. Now, this isn't always the case so please make sure you read the
user manual for your amplifier before making any connections. Because the speaker is wired between
the two positive terminals, one of those terminals needs to act sort of like the negative terminal.
In stereo or parallel mono mode the negative terminal acts as a reference and the positive
terminal provides a series of positive and negative voltages relative to that. However,
in bridge mono mode, both of these terminals will be actively contributing to the voltage.
While the positive terminal on channel A creates a positive voltage, the positive terminal on channel
B creates an equal negative voltage. This means that in bridge mono mode you'll have
double the voltage between the terminals than you would in stereo or in parallel mode.
Your amplifier's user manual will certainly tell you how to configure the amp and bridge mono.
Let's take a look at this QSC PL340 amplifier as an example. This amp is very straightforward when
it comes to selecting the mode. There's a single switch here that can be toggled between bridge,
stereo, and parallel. On other amps, you might find dip switches that are toggled according to
a chart found on the back panel of the amp. On the QSC PL340 amp, you've got the option to connect
the speakers with binding posts or with SpeakON cables. The binding posts are clearly labeled.
On this amp you'd connect the speaker between the positive terminal of each amp for bridge mono.
Your amp probably has a similar notation that looks something like this.
Using SpeakON cables can be a bit more difficult to understand, especially if
you're not familiar with them. So if this is your first time using NL2, NL4, or NL8
I'd recommend watching the video I created comparing the differences between those
types of connectors. I'll put a link here on YouTube or you can go to this URL.
For bridge mono mode with SpeakON cable, I can see here that it will use 1+ and 2+ on an NL4 cable.
This means you'll probably need to use an adapter made specifically for this purpose.
You'll need an adapter that adapts the positive pin of pin set 1 and the positive pin of pin set
2 to whichever pin set your speaker is designed to operate on. Again, if that doesn't make any sense
check out the post I wrote on SpeakON cables and I think it'll help you understand better.
And please, read your amplifier's user manual. Don't trust me on this. Some amps
are different. Reference your amplifier's user manual before making any connections.
So what's the benefit of using an amp in bridge mono? While there are also some disadvantages,
the primary advantage is that doubled voltage. And when you pair that doubled voltage with the
fact that each amplifier is only seeing half of the speaker's nominal impedance, it results in
you theoretically getting four times the power in bridge mono mode. Although the current limitations
of the amp's power supply and thermal limitations will prevent that from actually happening.
Looking at the specifications of the QSC PL340, you can see that each channel can provide 800
watts of power to an 8 ohm load in stereo mode and in parallel mono mode. Our math would suggest that
bridge mono would give you 3200 watts to 8 ohms. However, in bridge mono mode it's only rated to
provide 2600 watts to an 8 ohm load. The way to think about it is that bridge mono can supply
twice the power to twice the load. That way you keep the load per channel constant. For example,
this amp can provide 2000 watts at 2 ohms in stereo mode or 4000 watts to four ohms in bridge
mono mode. Double the power to double the load. It can provide 1250 watts to 4 ohms in stereo mode or
2600 watts to 8 ohms in bridge mono mode. Again, roughly double the power to double the load. The
robustness of the power supply and the components will ultimately determine the limitations.
It's very important to make sure you've taken the time to select an amplifier and
a speaker that will work together efficiently and safely. I've got a speaker specifications
guide to help you choose the right speakers at audiouniversityonline.com/speaker-specs-guide/
and I've also created a guide to walk you through selecting
the right amplifier for those speakers at audiouniversityonline.com/choosing-an-amplifier/.
Hit the "Like" button if this was helpful to you and I'll see you in the next video you.