Hello, I have a question about Audio isolation transformer breaking ground loop. It seems reasonable since the transformer provide another grounding point instead of the common ground. But the other end of the circuit, maybe it is a preamp or power amp, require power, so we have to connect signal ground to the power ground, so it may bring it back to the ground loop?
The language barrier is strong in this one. Not exactly sure what it is that you are confused by either. I'll give it a shot anyway.
Here's a typical ground loop situation:
And here's how it looks with an isolation transformer inserted:
Now currents can no longer circulate, as the voltage between signal and ground is magnetically couped to the other side.
The problem is that with a galvanic connection, any current flowing over the signal ground connection causes a finite voltage drop that is indistinguishable from an actual signal component.
In a more complex setup, you could still have one or more other ground loops, but this one at least has been eliminated.
Here's a typical ground loop situation:
And here's how it looks with an isolation transformer inserted:
Now currents can no longer circulate, as the voltage between signal and ground is magnetically couped to the other side.
The problem is that with a galvanic connection, any current flowing over the signal ground connection causes a finite voltage drop that is indistinguishable from an actual signal component.
In a more complex setup, you could still have one or more other ground loops, but this one at least has been eliminated.
Attachments
And in practical usage, it works very, very well. I have a collection of audio isolation transformers for use in difficult systems. The first thing to try is a ground lift, but if that does not work a transformer always does.
I often have to connect an audio source to processors and amplifiers that might be 100-300 meters away in a separate room on different power. The isolation transformer always works.
I often have to connect an audio source to processors and amplifiers that might be 100-300 meters away in a separate room on different power. The isolation transformer always works.
Another option that works: Monster Home Theater Reference PowerCenter HTS 7000 MKII | eBay ...has to be that exact model though, they aren't all equal.
I mean the output of the audio transformer maybe connected to a preamp or power amp circuit, so it require power supply, then I should connect the signal ground to the power supply ground, so the the ground loop problem may still exist because of that?
That sentence is very hard to understand.
If your system is unbalanced like normal home audio it will have just 1 conductor and the ground wire. You have to break the ground wire between your source and the amp or preamp to eliminate the ground loop. The isolation transformer does that for you. At the source the signal wire and the ground wire are connected to the 2 primary wires of the transformer. At the amplifier end, you do the same thing. There is now no direct connection of the ground from the source to amplifier. You have cut the ground loop.
If your system is unbalanced like normal home audio it will have just 1 conductor and the ground wire. You have to break the ground wire between your source and the amp or preamp to eliminate the ground loop. The isolation transformer does that for you. At the source the signal wire and the ground wire are connected to the 2 primary wires of the transformer. At the amplifier end, you do the same thing. There is now no direct connection of the ground from the source to amplifier. You have cut the ground loop.
Sort of. You at least have to make the ground loop high impedance for at least some ground currents. That's what a common mode choke on an individual AC cord is for in an audio system. Cutting the ground can work to, but sometimes safety can be an issue. Signal transformers work, but add a bit of distortion some people might prefer to avoid.
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Thanks for your reply, so the the secondary wires shouldn't be connected to the ground? I am asking this because the ground loop problem is cause by the refrigerator, when the motor run I can hear huge noise from the headphone output, If the secondary end of the transformer is connected to the ground, the problem is still here.
The secondary has to be connected to signal ground, yes. Usually signal ground will be connected to power (safety) ground.
I'm not sure that the refrigerator is causing a ground loop. Can you post a drawing of your system with the grounds included? Include the fridge in the drawing. 🙂
I'm not sure that the refrigerator is causing a ground loop. Can you post a drawing of your system with the grounds included? Include the fridge in the drawing. 🙂
Thanks for you reply, I am asking because the ground loop problem cause by the refrigerator and share the same AC line, if the secondary end of the transformer connected to the ground, the problem may not be solved. So I should connect the ground to the primary wires only?
Yes cutting (lifting) the signal ground often works in household systems because the current can flow thru the house wiring ground. In larger systems and balanced signals it doesn't always work. Sometimes a transformer is the only way to kill the noise. Most of us can live with a little transformer distortion to get rid of the awful Bzzzzzzzzzzz!
Of the transformer? No, ground should be connected on both primary and secondary. It can happen with strange grounds that not connecting ground on one side of the transformer can work, but it's not a good idea.
Can you post a diagram of drawing? The problem might not be a ground loop, but something else.
Here is what you can try.
Disconnect the signal between the headphone amp and the DAC.
Buzz gone? If yes, reconnect the DAC-AMP signal wire.
Disconnect computer to DAC wire.
Buzz gone?
This will help you know where the problem may be coming from.
Disconnect the signal between the headphone amp and the DAC.
Buzz gone? If yes, reconnect the DAC-AMP signal wire.
Disconnect computer to DAC wire.
Buzz gone?
This will help you know where the problem may be coming from.
I thought it should be pc and the refrigerator problem. I have tested this before, remove the power cord of the refrigerator the noise gone, or remove the usb cable to the dac, the noise gone too. I tested this with my laptop too, if the laptop connected to the charger having the same problem, when it is power by battery only, no noise at all. For my desktop PC, the noise is always here when the refrigerator's motor running at high speed .
Where does the HPA get power, from USB? If from AC, where does its power cord go?
I have seen conducted HF/RF AC ground hash make audible distortion in a dac. It must have radiated off in space with the USB cable and devices connected to the USB cable comprising an antenna.
I have seen conducted HF/RF AC ground hash make audible distortion in a dac. It must have radiated off in space with the USB cable and devices connected to the USB cable comprising an antenna.
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