Written by Rodger Ball

At the beginning of 2022, I had a new computer built by Scan Computers. It was specifically built for use with Davinci. When using Davinci I was aware of the graphics card making a noise as it was rendering, even when scrubbing on the timeline. It sounded distinctly digital and was annoying, to say the least. On further investigation, I realized it was coming from my speakers even with the volume turned down. I tried new cables, moving the cables to make sure they weren’t near any mains etc but to no avail, the noise persisted.

The noise itself seemed to be worse when the graphics card had a lot of work to do. I looked into this on the Internet in the usual manner but found it difficult to describe the noise so I wasn’t getting anywhere. There was a suggestion that the sound card was not properly installed, so I got in touch with Scan. I spoke to someone in their technical department but again found it difficult to describe the noise. They were very helpful but couldn’t give me an explanation.

My next move was to switch to some older speakers I’d bought from Maplins years ago. The noise disappeared but these speakers were not technically good enough for the job.

I decided to invest in some better speakers, namely the Presonus E5s. I was disappointed to find that the noise was back. This led me to believe that it wasn’t the fault of the speakers or their amps. I wrestled with the problem again changing leads etc.

One day whilst changing leads a light went on in my head. The old speakers that I’d bought from Maplins only had a live and neutral input from the mains, they were not connected to the earth. The speakers that were giving me problems had a 13amp plug feeding the amp so we’re connected to the earth. I decided to take a risk and disconnect the earth. low and behold the noise disappeared so it was a ground loop causing the problem.

Ever since my teens, I’ve had to deal with ground loops at one time or another, but they would usually manifest themselves as hum. It hadn’t occurred to me that digital noise could be the result of a ground loop.

I now knew what I was dealing with, but I didn’t want to leave the earth disconnected. I decided to consult the Internet again and was able to source a Ground Isolator. A ground isolator is a simple device which goes between the audio out of your sound card and the input of your speaker amplifier. When I say it’s a simple device I mean it merely consists of two isolating transformers one for each audio channel.

So if you are ever confronted with a similar problem ground isolators are available on the Internet.

Ground Loop Isolator with 2x Phono RCA L/R Sockets – Unbranded | CPC (farnell.com)