Fixing ground loops with transformers.
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- เผยแพร่เมื่อ 18 ก.ย. 2024
- While I have an adequate audio set up (well adequate for me), there are ground loops everywhere, picking up weird digital noise from the computer. Can I fix this with audio isoation transformers? We'll see.
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I had fun with a transformer recently, I used one to create a simple AC inverter using a cheap audio amp. Managed to get up to 120V AC from it.
I did try the same audio isolation transformers in my setup before and still had some noise on the output. I think this is because of the high parasitic capacitance between the two coils. I ended up using FeinTech ATG00101 transformers from Amazon and they completely eliminated the noise. I also checked the frequency response with the bode plot function of my oscilloscope and it was in a range of +/- 0.5 dB from 20 Hz to 20 kHz.
This reminds me of one time when I tried to make a diy computer audio amplifier. I used parts from 2 broken powered speaker sets, parts I had already and some parts I had to buy. It worked great, but from time to time it would make these buzzing and squeaking noises and I just never could figure out how to fix it. I never made a case for it so it was just a bare circuit board sitting on my desk and I thought prob was because of the lack of shielding thanks to the lack of an enclosure. Tho I remember hearing about ground loops online, but no good ways to fix them apart from good grounding techniques ie star grounding. Now I almost want to dig that thing out of my closet or wherever its laying around and try a transformer with it and see what would happen. I don't use it anymore these days I use wireless headphones, but if I still have it I'd like to try this.
Merry Christmas Clem
good work, Im lazy and bought the stereo ones from ebay car audio section haha
I've use this method to create an isolated audio output from car stereo to hook up a VU meter. Connecting parallel to output speaker cable does not work, also I find adding a couple of ceramic capacitors in parallel to the audio transformers cleans the audio signal further.
Ground loops do confuse me. I assume the ground is acting as a loop antenna.
Have a Happy New Year Clem.
There are some things I haven't totally worked out regarding ground loops. How do I prevent DC drift and over/undershoot on the isolated device? Should I add a large resistor to ground to prevent it from acquiring a bias? Is it simple to use both a high and a low pass filter to suppress ground loops while still allowing (desired) DC signals to pass?
Idont see why you wouldhave DC drift. They're not like capacitors so I wouldnt bother with the resistor. Hig and low pass filters won't do anything about a ground loop.
If the filter blocked the frequency of the ground loop it would have to, wouldn't it? The DC I'm worried about is any slow charge up of the isolated device if it isn't grounded. @@CoolDudeClem
Noise is high frequency badly filtered coming from the computer and similar equipment or switch mode power supplies. try to buy data cables with ferrite beads incorporated, you can try changing power bricks around or try a different power supply for the computer. You can build filters to fix this once you know where it's coming from.
Can you trace back the computer noises with the oscilloscope?
I wouldnt know how I would go about tracing the noise, all I do know is that the noise is comming from the computer and part of that was being picked up by a ground loop.
👍👍
Can't you fix the inversion by reversing the wires on one side of the transformer?
If you are getting steady audible noise through a line, the transformer will happily pass that noise along. It doesn't look any different to an actual audio signal.
There really is no need to reverse the wires, it's an audio signal. In most cases it makes no differnce if the signal is inverted or not, just so long as both channels are in phaze.