Yesterday I already documented in great detail and above all in practical terms the negative impact that ground loops can have in the PC and what this means for the individual ground paths. If you haven’t read this article yet, you should perhaps catch up on it quickly for a better understanding, because it explains a lot of things that I’m going to make a little shorter today so as not to repeat myself too much.
Today we want to complete the whole thing, because these problems do not only occur internally, but can also have a very negative effect on externally connected devices. Today I’m going to focus on the USB connection, because we’ve already covered this topic once before, but it was about analog signals. Today, however, we will be looking at two ways of eliminating this interference or at least suppressing it sufficiently.
Because one thing is a fact: clean galvanic USB isolation and suitable USB interference filters play an important role in improving data and signal integrity and protecting sensitive electronic devices, such as PCs and their peripherals, from potentially harmful electrical interference. These technical solutions are by no means “voodoo”, unlike hand-bobbin lace sheaths of various gold-plated speaker cables on virgin sapphire mounts, but are based on sound scientific principles and engineering practices aimed at improving the performance and reliability of USB connections. Especially in times of powerful and hungry graphics cards and extremely fast pulsating currents, this problem is becoming increasingly serious.
The ground loops mentioned yesterday naturally also have an effect on the analog branch, but there are of course many other reasons why something hums or hisses that should not hum or hiss and why or why you in particular are affected. If you break it down, there is a global and a local reason, but always in order, because sometimes both apply at the same time, so don’t get too excited! Let’s start with the global pandemic and leave the PC out of the equation. To do this, I’d like to refer back to an older study that I discussed years ago in an article on onboard sound.
The difference between analog and digital interference, especially due to interference and ground loops, can be illustrated quite well using the example of analog sound connections and digital USB connections. Both types of transmission are susceptible to interference, but in different ways and with different effects. Analog audio connections transmit signals through continuous electrical voltage changes that represent sound waves. This mode of transmission makes them susceptible to two main types of interference, namely the unwanted interference that occurred when external electromagnetic fields (from cell phones, radio transmitters, electric motors, etc.) interact with the analog signal path and add unwanted signals or “noise”. This can manifest as hum, buzz or noise and varies depending on the proximity and strength of the interference source. Since the analog signal is a direct representation of the audio signal, such interference can directly and audibly affect the audio quality.
The other cause is ground loops (hum loops). A ground loop occurs when two devices in an audio system have different electrical potentials and share a connection, resulting in an unwanted current flow. This often manifests itself as a low, steady hum (often at 50 Hz or 60 Hz, depending on the local power grid). Ground loops are a common problem in complex analog audio setups and often require special isolation or grounding solutions to eliminate them.
Digital connections such as USB transmit signals in the form of digital data packets consisting of binary code. This type of transmission offers some inherent advantages in terms of resistance to interference. Although digital signals can theoretically be affected by external electromagnetic fields, external interference in the signal path does not immediately lead to audible noise in the audio output. Digital transmissions can use error correction mechanisms to ensure that the received signal matches the transmitted signal. However, things become precarious when the ground line also comes into play. Short-term interference and EMI can cause audible errors because it can also affect the integrity of the data packets (“electrical noise”)
Digital audio transmissions via USB are largely immune to analog ground loops, as the data is transmitted digitally and the connection itself is less susceptible to the electrical interference caused by ground loops. USB audio interfaces above a certain price range can also offer galvanic isolation, which further reduces the potential for ground loops. There is no denying that digital audio transmissions via USB, for example, are generally more robust against interference and conventional ground loops due to their nature and the technologies used. While analog connections offer high audio quality under ideal conditions, they are also more susceptible to interference from external signals and grounding problems. The choice between analog and digital audio transmission ultimately depends on the specific requirements of the application, the equipment available and the environmental conditions.
But if all those who prefer digital are now hardly able to sit still with excitement: Now we’ll quickly move on to an analog interlude in what is actually a digitally oriented article. It has to be.
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