11/29/2023 0 Comments Audio ground loop isolator schematicUnfortunately, as I learned the hard way, the extender that I purchased fed DC ground and 5V signals through some of the wires of the "DDC" ethernet cable, so there was still a direct ground-ground path through the extender. The isolation was supposed to be achieved by running the HDMI through a HDMI-dual cat5-HDMI extender, which I figure used the balanced twisted pairs in the ethernet cables, so would not need a direct ground connection. I had already determined that the hum & buzz disappeared when the HDMI cable was unplugged, so the shields and grounds of the HDMI cable were definitely the path for the ground noise fed in from the satellite cable shield (noise also disappeared when the sat cable was unplugged). I thought that I could break the ground loop between my DirecTV box and my AVR by using an opto TOSlink cable for sound, and an "isolated" HDMI for video. Longer explanation of the HDMI issue below. My only recourse was transformer (jensen iso-max), which worked great, but was $$. Short explanation: HDMI extenders do not provide ground isolation. Ground loop isolators are extremely cheap and can mean the difference between a high quality electrical circuit and a poor one.HDMI cat5 extender won't break ground loop They also prevent hazardous interaction between users and high-voltage electrical systems that are meant to be safe. Ground loop isolators prevent unwanted noise in audio/video systems as well as the hum that a car alternator creates. Ground loop isolators are also used in antenna systems and routers that use more than one antenna to prevent radio interference from the device itself. Interference can be much more critical than this, however, such as in the case of transformers and other electrical supply systems that use a ground loop to prevent users from being shocked. This hum can also be heard in car stereo systems, in which the hum’s frequency depends on the engine’s RPMs. Most speaker systems use a ground loop circuit to connect two or more speakers together and the voltage difference between them is often responsible for an audible hum heard over the audio. Ground loop isolators are used in a variety of electrical systems, especially in audio/video devices. This allows the ground loop isolator to block any voltage spikes that may interfere with the circuit’s electrical signals. Ground loop isolators have a 1:1 ratio, meaning that they produce an output that is equal to their input. Ground loop isolators prevent interference in electrical ground loop circuits by using a small transformer that steps voltages from each circuit in a ground loop up or down, depending on whether the voltage difference is positive or negative. This is known as interference and can be hazardous, inefficient, and a nuisance in many electrical systems. However, if the ground wire has significant resistance and current, the voltage of the second circuit will be slightly lower than the first, causing a voltage difference that makes the ground wire no longer have a ground potential. Ideally, all circuits in a ground loop circuit have the same voltage potential. A ground loop circuit is one in which two or more circuits are connected to the same ground wire. A ground loop isolator prevents interference in a ground loop circuit.
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