Balanced audio explained FAST!

Today, we're going to be explaining as quickly as possible the difference between unbalanced and balanced audio connections. The question of what the hell is a balanced audio connection and why should I care is something that almost everyone dipping their toes into either high-end consumer audio or professional audio will at some point find themselves asking. So, what exactly is the difference? Let's break it down. The first thing we need to explain is that balanced versus unbalanced and single-ended versus differential are not the same thing. Most RCA connections, for example, are both unbalanced and single-ended. And most XLR connections are both balanced and differential. But balanced does not necessarily mean differential. And single-ended does not necessarily mean unbalanced. A bit of electronics 101. Voltage is a potential difference between two points. And so it has to be referenced to something. In a single-ended RCA connection, this is the positive signal level referenced to ground, which is the 0 volts reference point. In a differential XLR connection, it's called differential because instead of the signal being the level of the positive connection versus ground, it's the difference between the positive and negative connections, not ground. So single-ended versus differential describes whether the signal is being transferred via a single active connection versus ground, or the difference between two active signal connections. Balanced versus unbalanced, on the other hand, describes whether two conductors being used have identical impedances to ground. And we'll talk about why that's important with some examples. Let's look at a typical single-ended and unbalanced connection. In the case of an RCA connection, the center of the connector is the positive connector, which carries the signal itself, and the outer ring is a ground return connection. Since an electrical circuit needs a return path, you can't just connect one end of a battery and have it work. You need to complete the circuit, and analog audio is no different. This is by far the most common type of connection found in most audio equipment, especially products geared towards regular consumers. Our positive connection carries the electrical audio signal from one device to the next. Playing a sine wave, the voltage on this conductor will oscillate between positive and negative as indicated by the sine wave itself. The ground connection is fixed at 0 volts. It does not carry a signal. And the single signal carrying conductor is what makes this single-ended. This setup works but is unfortunately susceptible to external interference because it is unbalanced. It's called unbalanced because the impedance of each connection to ground is not the same. And so external electromagnetic noise picked up by the two conductors on the cable will produce different voltages on each. Noise picked up by the ground wire has a very low impedance path to ground and so it is effectively drained almost entirely but not on the positive connection which has a high impedance path to ground and so that noise remains. The receiving device is amplifying the level of the signal versus the ground reference of 0 volts. And so this minus this leaves us with noise still present on our signal that we picked up along the cable. To address this problem, most unbalanced connections will have a shield surrounding the cable and connected to ground at the source device, though sometimes both ends. This allows external interference to be picked up by the shield surrounding the conductors rather than the conductors themselves. The noise then follows the low impedance path to ground, and in ideal circumstances, nothing gets through the shield to reach either inner conductor, leaving us with a clean noise-free signal at the receiving end. But the shielding is mostly only effective at very high frequencies, and it's not going to do much for lower frequency EMI. So particularly with longer cable runs, you can still end up with quite a bit of noise even in the audible band remaining in your resulting signal even though the cable was shielded. This is where balanced connections come in as they can help to mitigate noise to an enormous extent. Most XLR connections are balanced and differential but will break down each aspect. Balanced requires that both of the signal conductors in a cable have absolutely equal impedance to ground. Not nearly equal, but absolutely equal. And it doesn't matter how this is achieved. In a balanced connection, external EMI will induce the same noise in both conductors since they have equal impedances to ground. Unlike our unbalanced example earlier where the differing impedance to ground on the two conductors yields a different induced voltage in each with a simple signal, I'm using a flat and constant DC signal here as an example. In an ideal scenario, there's no noise. So, the receiving device sees the difference between the positive and the negative, and we get a clean signal that reflects what the positive conductor was carrying. 1V minus 0 volt equals 1V. In this comparison example, which is balanced though not differential, we've picked up some noise. Though with the connection being balanced, the noise in both the positive and negative connections is identical. It causes a bump in the signal here and the difference here is also still 1vt. Any noise is canceled out since it affects both of these connections equally and the voltage or potential difference between them is unchanged. So this minus this is a noise-free signal. Balanced systems give you a huge level of passive noise rejection. But most balance systems in audio are also differential. Meaning rather than one active signal conductor, the negative conductor is also carrying an equal but opposite version of the positive. The difference between these at any given point is twice as much as if it were just the positive signal reference to ground in a single-ended system. This is why most balanced outputs on devices you'll see as being specified to have twice the output voltage of the single-ended outputs. They are differential. It's not that any particular conductor is actually carrying a higher voltage. In fact, the positive connection of the XLR output and the RCA output on most devices is usually shared and connected to the same circuitry, but rather just that on a single-ended connection, plus 2 VTs relative to ground is 2 VT, but plus 2 VTs relative to minus2 VVs in a differential connection is 4 V of difference between them, giving us a higher effective signal level compared to any remaining noise that we picked up, further improving the signal to noise ratio by about 60 dB on top of the passive noise rejection benefits that we got by the connection being balanced. Many XLR connections will then use a shield as well. So now you have protection from the shield, protection from the nature of it being balanced and the extra 60dB of signal to noise ratio from the higher signal level itself. Meaning that XLR connections that are both balanced and differential can be used for even extremely long runs without worrying about noise pickup pretty much at all. So most XLR connections, for instance, are both balanced and differential. But don't confuse the two. You can have a balanced system without it being differential like what we saw earlier. The negative connection on this XLR output is not doing anything. It's not carrying a signal at all, and it's actually got the same zero volts as the ground pin does. Both the positive and the negative have equal impedances to ground though. So, we still get the noise rejection benefits of balanced, though it is not a differential system. You can also have a differential system that is not balanced. If the impedances to ground on this differential XLR connection were not the same, it is considered unbalanced and we don't get the passive noise rejection benefits of being balanced since the differing impedances mean that the noise induced on each conductor will be different and therefore won't be passively canceled out at the receiving end. This is why balanced means the impedances need to be exactly the same, not almost the same. So, if a balanced differential system is better, why isn't everything balanced? Why are you single-ended at all? Well, the main reason is simply that it's more complex and expensive for a differential system. You have to have about twice as much circuitry since you need one amplifier for the positive output, one amplifier for the negative output rather than just the stuff for the positive. If you're talking about a DAC, then you also now need to have twice as many DAC outputs or channels since for each of the two stereo outputs in a twochannel system, there are now two polarities and you now need four DAC outputs in total, not two. So for DAX specifically, there are quite a lot of examples where the DAC itself is single-ended, providing a single polarity output for each channel and then an inverting op amp or circuit creates an inverted polarity version of that signal so that the product as a whole can still provide a balanced differential output even though the DAC itself was single-ended. Similarly, many amplifiers will accept a single-ended unbalanced input and convert it to differential internally so that they can still provide a differential output to the headphones or speakers. So, that's how balanced and differential audio works. But I think that now is probably a good time to clear up some myths and misconceptions about balanced audio as well. Firstly, the connector itself doesn't tell you whether something is balanced or differential or not. A quarterin TRS cable, for instance, is most commonly used for single-ended unbalanced stereo connections where you have one positive connection for the left channel, one positive connection for the right channel, and a shared ground return path. But that same TRS connector can be used for a balanced differential connection if it's only carrying a single audio channel since then it has one conductor for the positive polarity of that channel, one for the negative polarity of that channel, and a third for ground. Exactly the same as a three pin XLR connector. Same goes for headphones. A 3.5 millmter connector is single-ended if it's being used for two channels since it only has three contacts, but can facilitate differential if it's only being used for one channel. This is also why on some headphone amps you'll see the option for two channel 4 pin XLR balanced output which provides positive and negative for each of the two channels, but sometimes a dual 3 pin XLR where each output connector provides the positive and negative outputs for one channel only. The ground though isn't actually connected since headphones aren't grounded at all. Additionally, just because something has an XLR output on it, it doesn't necessarily mean that it is actually either balanced or differential. A lot of products will have an XLR output or maybe even a pentagon output simply for the purposes of convenience. They can be fully single-ended and unbalanced devices, but they just put the XLR connection on there so that you don't need to use an adapter if your headphones are balanced. Adapters are a critical thing to talk about because a lot of people may be putting their devices at risk with them. If you have a device with a balanced differential output, you cannot always safely adapt this to a single-ended input, be it the input on an amplifier or a single-ended headphone. A lot of people say that they want to do this because they feel that the balanced output on their particular device sounds better. But even if that might be true, you'd need to use a fully balanced connection in order for it to stay true. There's two main ways in which balanced to single-ended adapters are set up. The first is that they just leave the negative connection floating. So, the only things that get connected are the positive signal carrier and the ground connection. And in this case, you're just using a single-ended connection. This is exactly what the RCA output of 99% of devices does. And so, using one of these cables, it will work, but it is no different to just using the RCA output of your device. It is no longer a balanced connection because the positive and the ground connection don't have the same impedance to ground. And it is also no longer a differential connection. you'll get the same voltage as if you connected to the single-ended output because you're not looking at the difference between the positive and negative. The negative isn't connected. So, there's no advantage to doing this. You're better off just connecting to the single-ended output of your device. But, it also should just work. The real risk with trying to adapt balance to single-ended, however, is that a lot of adapters short the negative polarity of the output straight to ground. And this means that the negative polarity output of your device is seeing a zero ohm load. it is being straight up shortcircuited. At best, this means that your device is going to be massively overloaded and will not be performing at its best. And in many cases, it could be damaging the device either instantly or over time. If you feel that the balanced output of your device sounds better, you need to use the balanced output with a balanced connection and just generally shortcircuiting stuff and potentially breaking things generally considered bad. I hope you found this video useful and entertaining. And if you want to help support more educational content like this, then for your next audio purchase, be it cables, headphones, speakers, amplifiers, DAXs, or anything else at all, consider purchasing from headphones.com. They make everything that we do on this channel possible. And if you buy with headphones.com, you get a 365day return policy and excellent customer service as well. In the meantime, if you wanted to ask any questions about balanced or single-ended audio, DAXs, amps, headphones, anything else at all, then come and say hey on the headphones.com Discord server or the Headphones.com forum, and I and other wiggly air enthusiasts will endeavor to help. I'm Golden Sound. 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