6KHz interference from computer audio? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: October 31, 2022, 04:24:55 am
content: I am working with sound a little and I noticed for some reason, there is a transient noise that comes on for maybe 20-30 minutes on the left audio channel from my PC. When I disable PC audio, power down the amp or remove the amp feed cable, it goes away. I had it happen at 3am and like 4pm.When I measured it with the smartphone app, it looked like a 6.125KHz tone. The right channel is not effected.Before I start trying to hunt it down, I wonder if anyone ever saw something similar? North America 120V 60Hz split phase feed to a house.I figure if I get some kind of isolated sound system using the digital output, it might go away, but its none the less curious.Has anyone seen this before? I know how to get rid of it, but I wonder if its a sign of something bad that needs rectification. I was not planning on doing a EM study right now.It seemed consistent with the annoying-as-fuck noise that was coming from alot of SLC capacitors inside of old equipment I was restoring. Neighbors got some toys?Thinking about buying a HV differential probe, but that would just point to the problem, while with the same money I could probobly solve it.

author: A.Z.
author_rank: Super Contributor
timestamp: November 01, 2022, 07:29:05 am
content: did you consider implementing some simple LISN devices ?

author: radiolistener
author_rank: Super Contributor
timestamp: November 01, 2022, 07:35:03 am
content: usually such noise is interference from switching mode power supply regulator in the PC/notebook/tablet-pc. It's noise depends on CPU load.

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2022, 07:55:34 am
content: Rebonjour, All PC PSU are noisy SMPS.You are seeing a typical PSU or conducted EMI noise, freq and ampl is depending on SW running, PSU loading, etc.Since 1980s we worked on isolation PSU and shielded digital audio transformers to solve this.See our AES/SMPTE/NAB papers and seminars.We suggest to avoid any analog audio from the PC/sound card.Best solution is digital audio from the PC like SP/DIF or TosLink optical, digital output to a separate high quality DAC.Low budget: External DAC like Sound Blaster Creative Audiologyhttps://fr.creative.com/p/sound-blaster/sound-blasterx-g6#buy$100High end: Weiss Engineering DAC 501.https://weiss.ch/products/highend-hifi/dac501/$3..10kHappy listening!Jon

author: A.Z.
author_rank: Super Contributor
timestamp: November 01, 2022, 08:33:43 pm
content: ahem "we suggest".... WHO is that "we" ??

author: coppercone2
author_rank: Super Contributor
timestamp: November 01, 2022, 08:53:53 pm
content: well I tried an audio isolation transformer on the analog line, unlikely as a solution as this was, and it did not help, so I either need a sound card / external sound module that uses digital or optical communication

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2022, 09:06:09 pm
content: "We"....me, my firm, colleagues and industry connections.Sécurité considerations restrict more specific infoJ