feedback in headphones (yes i rtfm)

gothmog123 · 2020-10-20 13:41:27

Sorry maybe a noob post but I actually read and tried everything in the pulseaudio/alsa troubleshooting wiki.

I have a dell latitude e6230. All sound recorded through the headphone combo jack contains a constant feedback/hissing kind of sound. The internal mic no problem.

Could anyone help?

Last edited by gothmog123 (2020-10-20 14:01:18)

V1del · 2020-10-20 14:15:07

That statement in the first sentence is as posed close to impossible to achieve and basically always a(not necessarily harmful or deceivingly meant) lie. Instead of such a blanket statement show what you did by posting the outputs of commands of the research you did, which conclusions you drew and which changes resulted on your system.

That out of the way make sure you don't have a mic boost enabled and make double and triple sure that your jack is actually properly connected, a lot of issues in that regard may arise from being a few mm off with the plug. It's also possible that it is incorrectly shielded or so. Have you tested the same mic on other hardware/other mics on this hardware?

Maybe post

arecord -lL
amixer -c$index of the relevant card from arecord -l$
#If applicable and during a recording
pacmd list-sources
pacmd list-source-outputs

gothmog123 · 2020-10-20 14:22:51

V1del wrote:

That statement in the first sentence is as posed close to impossible to achieve and basically always a(not necessarily harmful or deceivingly meant) lie. Instead of such a blanket statement show what you did by posting the outputs of commands of the research you did, which conclusions you drew and which changes resulted on your system.
That out of the way make sure you don't have a mic boost enabled and make double and triple sure that your jack is actually properly connected, a lot of issues in that regard may arise from being a few mm off with the plug. It's also possible that it is incorrectly shielded or so. Have you tested the same mic on other hardware/other mics on this hardware?
Maybe post
arecord -lL
amixer -c$index of the relevant card from arecord -l$
#If applicable and during a recording
pacmd list-sources
pacmd list-source-outputs

sorry it's not a lie, but I actually just found the cause. It only happens when AC is plugged in and not when running on battery. Does this get us closer to the root of the problem?

V1del · 2020-10-20 14:35:09

depends, do you run a power management software that changes behaviour/power information for kernel modules depending on the state?

If not I'd assume that this is indeed an issue with electrical interference that's unlikely to be adjustable in software, play with power_save_controller and power_save module options for snd_hda_intel.

Maybe also try a UEFI/firmware update, if anything has a noticeable influence here it might be those.

Last edited by V1del (2020-10-20 14:36:42)

ewaller · 2020-10-20 14:41:32

Sounds like a hardware problem. It could be a few things. It could be a poorly shielded microphone. A poorly shielded cable is subject to interference from changing E (electric) fields near the cable. E fields around batteries don't change (much), power supplies running on the mains is a different matter. Regardless, almost no cables are shielded against B fields (magnetic); and there are many opportunities to encounter changing B fields around switching power supplies. Start by rerouting your cables and see (well, hear) if there are differences as you move the cables around.

The other possibility is that the power supply is letting the 50Hz (or 60Hz) frequency ripple through to the DC output. This is much less prevalent than it used to be, modern switching supplies providing very low core voltages have gotten pretty darn good.

Also, does anything else happen when you are running on mains power? Do LCD backlights go to full brightness? Do any fans start? Does the CPU clock speed ramp up?

Arch Linux

#1 2020-10-20 13:41:27

feedback in headphones (yes i rtfm)

#2 2020-10-20 14:15:07

Re: feedback in headphones (yes i rtfm)

#3 2020-10-20 14:22:51

Re: feedback in headphones (yes i rtfm)

#4 2020-10-20 14:35:09

Re: feedback in headphones (yes i rtfm)

#5 2020-10-20 14:41:32

Re: feedback in headphones (yes i rtfm)

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