Force software mixing for USB-to-stereo adapter?

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MatMacKenzie
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Force software mixing for USB-to-stereo adapter?

Post by MatMacKenzie »

Hello, people--

I'm using Mint 18.1 on an old Thinkpad (R500) to play DVDs, and the stereo jack gets buzzy when I plug in an external monitor. It's not a ground loop problem--still happens on battery--so I think the hardware is just flawed. It even happens in BIOS. So not a driver issue, either.

To try to work around this I bought a cheap little USB-to-stereo jack adapter. Sadly, this has the same buzz; but _not_ while in BIOS. At that point I think Linux USB audio code is using the audio hardware as an optimization. I'd love to have audio data go from DVD to CPU to USB without involving the hardware. I'm pretty sure that would bypass the source of the buzz.

I'd be happy with either a GUI utility which lets me control this or a configuration setting in some .rc file. But web sites about this sort of thing get into so many little options I'd need hours to work out a starting point. If someone out there has already done this, please let me know how.

Thank you!

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phd21
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Re: Force software mixing for USB-to-stereo adapter?

Post by phd21 »

Hi "MatMacKenzie",

Welcome to the wonderful world of Linux Mint and its excellent forum !

It would help to know more about your system setup. If you run "inxi -Fxzd" from the console terminal prompt, highlight the results, copy and paste them back here, that should provide enough information.

You can try this with the default sound card, or with the USB sound card, or both.

FYI: There are some really nice graphical (GUI) programs for sound that start with "Qas", like the fantastic "Qasmixer", in the Software Manager or Synaptic Package Manager (SPM) that you can install and use. Sound "Mixers" can be a little confusing if you are not familiar with them. If you bring up "Qasmixer" and make it fullscreen, on the right side you will have mixer devices where you can control your system sound. If you do not see the mixer devices, hit "F6". The mixer item "sysdefault" will show all installed sound card device options, and you will have various options to adjust various volume controls using "sliders" which you can turn off and on using the "dot" below the volume slider. There are also various other check boxes below that you can use, and depending upon your sound card(s) that sometimes includes headphone checkboxes and or sliders as well, like "Headphone Jack Sense".

"Buzzing" or feedback can be caused by various things, usually because you have the volume too high on some setting, or you have something plugged into the wrong jack, sometimes because you are next to a source of interference like florescent lighting (includes CFB), power adapters, power cables, etc...

The applications included are:
- qasconfig - browser for the alsa configuration tree
- qashctl - mixer for alsa's high level control interface
- qasmixer - desktop mixer with features similar to alsamixer

Qasmixer is a desktop mixer application for alsa's "simple mixer interface" and offers features similar to alsamixer. it also features a sytem tray icon with basic mixer functionality.

Hope this helps ...
Phd21: Mint 19.2 Cinnamon & xKDE (Xfce) & KDE Neon 64-bit Awesome OS's, Dell Inspiron I5 7000 2 in 1, Dell OptiPlex 780 Core2Duo E8400 3GHz,4gb Ram, Intel 4 Graphics. I use KDE?:https://opensource.com/life/15/4/9-reasons-to-use-kde

MatMacKenzie
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Re: Force software mixing for USB-to-stereo adapter?

Post by MatMacKenzie »

phd21--

Thank you! I don't have a solution yet--not ever sure there is one--but that was a lot of info.

Interesting that even fluorescents can produce noise. I hadn't heard that one. In my case the noise is only when I plug in a second monitor (actually, I mostly use a projector; this is all for movie nights)--and sounds exactly the same if the monitor is off. Turning other things off in the room, changing wall sockets, running the laptop from its battery, and moving to another part of the room also have no effect. That's why I figure it's internal.

The buzz gets louder if I turn up the volume on the speakers. The projector produces a lower-frequency buzz than the TV. Just noticed that today. That does make me wonder what else I've missed.

Unfortunately, to get a good movie volume I have to turn it up enough for the buzz to be pretty distracting.

Here's what I get from inxi -Fxzd. As you can see, it's a tired old second-hand machine off Ebay, but fine for Xfce. I've taken out some entries for brevity. Chances are the size of the SSD doesn't make a difference. If any of this suggests something to you I'll be happy to hear it. If not, thanks for your time.

System: Host: Mat-LGM Kernel: 4.4.0-21-generic x86_64 (64 bit gcc: 5.3.1)
Desktop: Xfce 4.12.3 (Gtk 2.24.28) Distro: Linux Mint 18.1 Serena
Machine: System: LENOVO (portable) product: 2718A16 v: ThinkPad R500
Mobo: LENOVO model: 2718A16 Bios: LENOVO v: 7YET45WW (1.15 ) date: 09/08/2008
CPU: Dual core Intel Core2 Duo T9600 (-MCP-) cache: 6144 KB
flags: (lm nx sse sse2 sse3 sse4_1 ssse3 vmx) bmips: 11170
clock speeds: max: 2801 MHz 1: 800 MHz 2: 1600 MHz
Audio: Card-1 Intel 82801I (ICH9 Family) HD Audio Controller
driver: snd_hda_intel bus-ID: 00:1b.0
Card-2 Generalplus driver: USB Audio usb-ID: 006-002
Sound: Advanced Linux Sound Architecture v: k4.4.0-21-generic

itsme4401
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Re: Force software mixing for USB-to-stereo adapter?

Post by itsme4401 »

A wild shot:
Ever tried to plug all computer-connected apparatus in the same wall-socket? (Thus excluding earth-loops)
This gave me the thought (I had such a noise once myself):
In my case the noise is only when I plug in a second monitor (actually, I mostly use a projector; this is all for movie nights)--and sounds exactly the same if the monitor is off. Turning other things off in the room, changing wall sockets, running the laptop from its battery, and moving to another part of the room also have no effect. That's why I figure it's internal.
More or less Off-topic: I hope my English is adequate enough to be understood for your trouble-shooting.

Hoser Rob
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Re: Force software mixing for USB-to-stereo adapter?

Post by Hoser Rob »

itsme4401 wrote:A wild shot:
Ever tried to plug all computer-connected apparatus in the same wall-socket? (Thus excluding earth-loops)
This gave me the thought (I had such a noise once myself):
In my case the noise is only when I plug in a second monitor (actually, I mostly use a projector; this is all for movie nights)--and sounds exactly the same if the monitor is off. Turning other things off in the room, changing wall sockets, running the laptop from its battery, and moving to another part of the room also have no effect. That's why I figure it's internal.
More or less Off-topic: I hope my English is adequate enough to be understood for your trouble-shooting.
I was thinking similarly ... not necessarily all in the same AC outlet but do experiment with that.

MatMacKenzie
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Re: Force software mixing for USB-to-stereo adapter?

Post by MatMacKenzie »

itsme4401 and Hoser Bob--thanks for the idea. I just pulled out an extra power strip and tried it.

Sadly, that didn't work either: same old hum whether the projector was plugged into the same outlet as the speakers or the other outlet. And those handy qa* utilities from phd21 present very few options for the USB-to-stereo adapter. Basically, you can mute it.

But maybe I'll think of something else to try later on.

itsme4401
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Re: Force software mixing for USB-to-stereo adapter?

Post by itsme4401 »

@MatMacKenzie: Sorry for not giving you a solution. Thanks for your feed-back.

MatMacKenzie
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Re: Force software mixing for USB-to-stereo adapter?

Post by MatMacKenzie »

Hey folks--

For the sake of closure, I'll never know what the problem was exactly, but after all my zany ideas about drivers and hardware layers, the solution was to simplify the wiring at the speaker end. My mystery buzz goes away if the computer is the only audio source.

Thanks again for all the tips!

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