Maybe you want to avoid using as much cable as possible in your speaker to amp wiring, or perhaps you want fewer wires cluttered at the back of your A/V. Whatever the reason, whether a set of speakers can share the same common ground has been a question that sparks a lot of conversation in the audio world. So, after hours of researching, here is what I found.
Can speakers share the same common ground? If the speakers are connected to an amplifier or receiver with a single-ended output, they can share a common ground. However, if the speakers are connected to an amplifier or receiver with a bridged (or differential) output, they cannot share a common ground. That’s because differential output amplifiers have no common ground.
Whether or not a set of speakers can share a common ground depends on the amplifier or receiver they will be connected to. Depending on the manufacturer, an amplifier or can either be single-ended or differential. I’ll explain the difference between the two and why it’s important if you want your speakers to share the same common ground.
Later in the article, I’ll give you tips on how to find the type of outputs your amp or receiver has. Let’s get into it.
Types of Amp/Reciever Outputs
1. Single-ended Output Amplifier
With single-ended output amplifiers or receivers, the positive output terminal is the active terminal, and the negative terminal is the common ground.
Essentially single-ended output amps transmit audio signals to speakers through the positive (+) output terminals, and the negative (-) output terminal is the ground.
This type of output makes it possible for multiple speakers to share a common ground. So, basically, you can connect all the negative terminals of a speaker to a single negative output terminal on the amplifier.
Inside some single-ended output amps or receivers, you will find that all the negative output terminals are connected together with either a wire or busbar.
Single-ended output amplifiers or receivers don’t only allow multiple speakers to share a common ground; it has other benefits.
Firstly, if your speaker has an L-Pad Attenuator, it will only work with a single-ended output amp or receiver. Although L-Pad attenuators are not very common in recent speakers, you will find some decent speaker cabinets that still use this technology. And they will only work with single-ended amps.
Another speaker accessory that requires single-ended output amps or receivers to work is the speaker selector switch. This means, in order to connect multiple speakers to an amp using a speaker selector switch, the amp’s negative terminal must be a common ground.
Single-ended output amps were the standard type of output for speaker amplifiers and receivers back in the day. Almost every power amplifier or receiver back then had a single-ended output.
However, as technology advanced, a new type of output terminals was developed for power amps and receivers. And these are the bridged amplifier output.
Bridged Output Amplifier
Bridged Output amplifiers (also known as differential output amplifiers) transmit equal but opposite voltage through the speakers’ positive and negative output terminals. This means both the positive and negative terminals are active.
This configuration doubles the voltage that is sent to the speakers. And it also increases the speaker output level up to 4 times what a single-ended output amplifier or receiver can deliver.
As you can already tell from this brief explanation, this configuration is completely different from a single-ended output amp. Bridged output amplifiers and receivers have no common ground. The negative terminal also carries a signal, so you should never connect it to ground.
It’s also a bad idea to connect it to any other terminal on the amplifier as if they were common ground. That’s because each terminal on a bridged output amplifier transmits a signal, and connecting them can be a hazard.
When you connect the negative terminal on the amp to another terminal or even to ground, you are essentially shorting out a voltage source. That can lead to a high current in the amplifier. And if the amp or receiver has no overcurrent protection, this will easily damage it.
With a differential amplifier, you should also never connect multiple speakers’ negative terminal to a single negative terminal on the amp. Each speaker should have its own terminal to connect to.
Most speaker amplifiers and receivers made recently have a bridged or differential output. It is much more efficient compared to single-ended outputs because it can deliver twice the voltage to speakers. Also, differential output amps or receivers can deliver noise-free signal to speakers over a long distance. That’s because they are balanced outputs.
How to Know an Amp or Receiver Output Type
One key takeaway from everything we have talked about so far is whether multiple speakers can share a common ground ultimately depends on the type of amplifier or receiver outputs they will be connected to.
If you own a single-ended output amp or receiver, multiple speakers can share a common ground, if you own a differential output amp or receiver, the speakers can’t share a common ground, or in effect, there is no common ground to share.
But the question is, how do you know the type of output your amp or receiver has? Follow these tips.
1. Read the owner’s manual
A simple way to know your amp or receiver’s type of output is to read the owner’s manual. If the amp or receiver’s unit manual is still available, take a moment to read it. It will be mentioned somewhere in the manual that it’s either a single-ended or a differential amplifier.
You can always look online for the owner’s manual of your amplifier or receiver if you don’t have the paperback.
2. Contact the manufacturer
Although you can find this information on the owner’s manual of most amps, sometimes that’s not the case. Some manufacturers choose not to state whether the amp or receiver unit is single-ended or differential in the manual.
If you happen to be in this situation, reach out to your amp or receiver manufacturer and ask them about it. A phone call is always faster, but you can send them an email or fill a support form on the manufacturer’s website to ask them about it.
3. Check inside the unit if the negative terminals are connected together
If you are handy with tools and a bit technical, don’t be afraid to open your power amp or receiver unit. Inspect the negative terminals from the inside to see if they are linked together with a busbar or wire.
If the negative output terminals are linked together with a busbar or wire, it means the amp or receiver is a single-ended unit; hence it has common ground. If they are not linked, then the unit is a differential output amp or receiver.
Do Speakers Need a Ground?
Speakers are resistive loads to an amplifier or receiver; hence they don’t need a ground. But they may have to be connected to the common ground if the amp or receiver powering them is a single-ended output unit.
This is not the case for a differential output amplifier because there is no common ground. So attempting to ground the negative terminal while it’s connected to a differential amplifier will damage it.
Since most amps and receivers these days are differential, you should probably not bother yourself with grounding speakers. They will work just fine without any issue.
In summary, if the amp or receiver the speakers will be connected to are single-ended, multiple speakers can share a common ground. You can do this by connecting the negative terminals of all the speakers to a single negative terminal on your amp or receiver.
However, chances are your amp or receiver is not single-ended. That’s because most amps and receivers these days have bridged (or differential) output. Both the negative terminal and positive terminal of bridged output amplifiers send a voltage signal to the speakers, so there is no common ground. Hence you can’t connect multiple speakers to a single terminal on the amp or risk damaging it.