Question Video capture card static noise

[InsanityCrescendo]

I have the Powertech CAB-H164 external video capture device which is an inexpensive device but seems to work fine. The only problem I have is that recording sound seems to produce a background static noise. The way this thing works is you connect the hdmi from the source (Android TV box in my case) and then you connect the usb 3.0 to your pc.

The ways that you can record sound are two (the two I know at least):
- From the usb 3.0 of the device to the pc usb (with a male to male usb a cable): Windows will detect the device as a usb microphone
- From the 3.5 "audio out" jack to the pc's "mic in" jack (with a 3.5m male to mal cable): Windows will detect the device as a microphone
*Software used: OBS (I also tried Audition to make sure)

I've tried both ways and the static sound is there on both. The only difference is that via the usb the sound is more of a "hiss" while with the 3.5mm jack it's more of a crackling sound.

Now, as far as troubleshooting goes:
- If I connect a pair of earphones on the 3.5 sound out jack of the device the sound I hear is perfectly clear. So that leaves out a faulty video capture device or hdmi cable,
- I tried other sources other than my TV box and the results are the same. So that leaves out a problematic source device
- For connecting the 3.5mm to the PC: I tried both the front panel mic-in hole and the hole in the back of the tower

So I don't get how I can hear sound fine (from the "sound out" jack of the device) but transmitting it to the "mic in" jack of the pc it creates this static.

EDIT: Added a schematic of the two configurations

 

[Ralston18]

Audio loop? Ground loop?

Some connection path where Device A connects to Device B which connects to Device C which connects to Device A again.

Any sort of circular connections between the devices?

Does using the earphones break some looping connection path?

Sketch out a simple diagram showing all devices, ports, and cables. Any loops?

 

[InsanityCrescendo]

Audio loop? Ground loop?

Some connection path where Device A connects to Device B which connects to Device C which connects to Device A again.

Any sort of circular connections between the devices?

Does using the earphones break some looping connection path?

Sketch out a simple diagram showing all devices, ports, and cables. Any loops?

I edited my post to include the schematic. I don't think there are any loops happening. It's not a difficult setup anyway.

 

[Ralston18]

As I understand the diagram there is a physical loop shown in the "Crackling" diagram.

From PC via 3.5 mm cable to the 4K capture device and then a return path from the 4K capture device via 3.0 USB cable back to the PC.

Also, the 3.5 mm cable (TR, TRS, TRRS) may be a problem.

The "Hissing" diagram may also contain a loop but that would/could be within the cables being used.

FYI:

https://www.cablechick.com.au/blog/understanding-trrs-and-audio-jacks/

If there is a mismatch in the standards and/or plug configuration being used that also causes problems.

It seems a simple setup but remember that each cable contains multiple wires and some corresponding number of pinouts.

All (pinouts) must match between plugs, ports, and host devices.

And you must also include electrical/power connection paths.

 

[InsanityCrescendo]

As I understand the diagram there is a physical loop shown in the "Crackling" diagram.

From PC via 3.5 mm cable to the 4K capture device and then a return path from the 4K capture device via 3.0 USB cable back to the PC.

Also, the 3.5 mm cable (TR, TRS, TRRS) may be a problem.

The "Hissing" diagram may also contain a loop but that would/could be within the cables being used.

FYI:

https://www.cablechick.com.au/blog/understanding-trrs-and-audio-jacks/

If there is a mismatch in the standards and/or plug configuration being used that also causes problems.

It seems a simple setup but remember that each cable contains multiple wires and some corresponding number of pinouts.

All (pinouts) must match between plugs, ports, and host devices.

And you must also include electrical/power connection paths.

I tried the "crackling" configuration but instead of connecting the 3.5mm cable from the capture device to the same PC that I also have the usb connencted to, I connected (the 3.5mm cable) to another pc and recorded the sound. It no more sound like a crackling sound, so I guess there probably was an issue with loop back in the original "crackling" schematic but it now sounds like hissing. In this new configuration there can't be any loop backs.

Should I try a mono 3.5mm cable?

 

[Ralston18]

No cracking is progress.....

I am not aware of any reasons for not trying "mono" just as a matter of elimination.

However, if possible try another known working (no hissing) stereo 3.5mm cable. Pay attention to standards.

Just be methodical in your testing and change only one thing at a time. Keep notes.

Keep in mind that the physical cable(s) may not necessary form a loop. It is some circular connection path formed within the devices, cables and their respective plugs, and ports. Be they 3.5mm mono, stereo, HDMI, USB, or otherwise. Some adapter perhaps.

The loop itself is unlikely to be visible and only discoverable by mapping pinouts and probably the use of a multimeter.

If the hissing cannot be stopped then I suggest moving your thread over to Audio & Home Theater. There are some experienced audiophiles thereabout who may spot something within the posts.

And thus offer other ideas and suggestions.

 

[InsanityCrescendo]

No cracking is progress.....

I am not aware of any reasons for not trying "mono" just as a matter of elimination.

However, if possible try another known working (no hissing) stereo 3.5mm cable. Pay attention to standards.

Just be methodical in your testing and change only one thing at a time. Keep notes.

Keep in mind that the physical cable(s) may not necessary form a loop. It is some circular connection path formed within the devices, cables and their respective plugs, and ports. Be they 3.5mm mono, stereo, HDMI, USB, or otherwise. Some adapter perhaps.

The loop itself is unlikely to be visible and only discoverable by mapping pinouts and probably the use of a multimeter.

If the hissing cannot be stopped then I suggest moving your thread over to Audio & Home Theater. There are some experienced audiophiles thereabout who may spot something within the posts.

And thus offer other ideas and suggestions.

The weirdest thing about all this though is that if I directly connect my earphones in the capture device I can hear the sound perfectly clear. So I really don't get why passing it to the pc suddenly creates static. Even on a totally separate pc. I'm not that into all the sound stuff, but I would think that this would be easier to solve

 

[Ralston18]

All the more reason to move this thread to audio.

Remember the PC's motherboard likely has an integrated sound card and/or a slotted card installed. Or even a USB sound card.

The issue may be within the connection between the host PC and capture device. Versus the connection between earphones and capture device.

Different plugs, ports, and cables.

It does not take much to have problems.....

Moving thread to audio.