Some sort of audio interference

I have a bit of a weird setup going. The overall goal is to have two PCs partially sharing audio. The ideal setup is to have PC1 recieve all audio from PC2, but PC2 only receives the audio from the mic attached PC1. I have gotten this to work, but I get a lot of interference. I am far from an audio expert so I have no idea what kind of interference this is (Audio sample in youtube video below). I would like to know if there may be something inherent to my setup that would cause this, or otherwise a way to filter out the interference.

The primary issue is the audio coming from PC2 speaker port (combo speaker/mic?) to PC1 line in, so everything below, unless otherwise specified, is referring to that.

Sample of interference:

The “Sabrent” mentioned below is this:
PC1 has a USB DAC for my headphones and mic.
PC1 Line in is connected to PC2 Sabrent USB speakers (combo port?) with a 3.5mm cable.
PC1 is set to “listen to” line in and playback through the USB DAC with windows control panel sound.

I have tried using Equalizer APO, following this video( which does negate most of the noise, but only when applied to my USB DAC (an output), which effects all audio, and is something I don’t want. Sadly when applying it to Line in, nothing happens, which must mean windows listen/playback happens before Equalizer APO can do its thing.
Latency is not an issue, as long as it is consistent, as voice, and in theory only voice, will be coming in on line in.

Please do let me know if more details and what additional details would help.

So, this is exact reason why balanced leads are a thing. Unfortunately, if your DACs don’t have XLR input/outputs, then you are kind of SOL.

Is there a reason why you are not using an external mixer instead?

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No, I just have no idea what I’m doing. When I first thought of this idea I did think a mixer would be the best way to go. Then I remembered Line out and line in on the back of the PC, and how overkill mixers seemed for my setup.

My DAC is very basic: Syba USB 24 Bit 96 KHz DAC Digital to Analog Headphone Amplifier 2 Stage EQ Digital / Coaxial Output and RCA Output SD-DAC63057, information not available: Home Audio & Theater
I’m really not familiar with audio hardware. If you are willing, I’m open to any recommendations you provide.

Edit: Just to clarify my setup in the most basic way I can think of:
I want the audio from 2 PCs going to my headphones, and I want my microphone going to both PCs.

A mixer may make this easy, but yes it is overkill.

There is a difference between line out and headphone/speaker out and that has to deal with, impedance, voltage, and gain.

So that we use the correct technical terms, let me state how your setup should be:
Line-out of PC 2 should be going into Line-in on PC1
Line-out of PC1 should be going into Line-in on PC2
Microphone input should be (logically) routed or split to go to PC2 via Line-out of PC1
The Line-in of PC1should be (logically) routed to the Headphone/Speaker-out of PC1.

Now, since you are using Line-out to feed a microphone in, you need to adjust the gain on PC1’s Line-out so that you can lower the noise ceiling and also bring downs some of that voltage that you are passing along. Microphones are very sensitive devices while speakers are less sensitive. You may still get noise but that will lower a lot of that interference that you are picking up which is actually EMF. Computers are pretty noisy.

Question: IS there are reason why you are not running the Syba on both machines?

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Regarding the physical setup of the computers, that is kinda the problem with PC2. It ONLY has a combo port on the back, which is why the Sabrent device was added (I already had it lying around). I did look around for an USB device with line in and out, but couldn’t easily find anything.

I’ll take any recommendation for mixer’s you can offer. The simpler, and smaller, the better. Though if there is an easier way, audio quality from the second machine does not matter very much. So if there is a way you know to do some sort of filtering via software, even if the audio quality is reduced, that would be fine.

Currently I have this setup:
Sabrent speaker port of PC2 going to line in on PC1
Line out of PC1 going to the Sabrent Mic port of PC2
Microphone is set to listen, and playback on Line out. (This is working with the same bad audio)
Line in of PC1 is set to listen to my USB dac. This is also working and is what was recorded.

Answer: If you mean why I don’t have 2 Syba’s, it’s because I already had most of this lying around and wanted to minimize cost and additional desk space being taking up.
If you mean why I don’t have a feed from the second machine into the Syba left most port on the front, I did try that, and I got audio from the second machine, but it disabled all other audio over usb.

Interesting and interesting. I don’t have any recommendations for USB attached Mixers. I am old school but have not need for that with PC stuff, I don’t stream or do digital DJing (yet.)

Hopefully someone here that streams would have some better advice for that.

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Could be the two PCs sitting at different “ground” levels (because they both have separate power supplies).

One thing to try is to get a “hum eliminator” (Behringer HD400 being a cheap example).

Was going to say, get a mixer.

Yamaha AG03 could work for you.
Hook it via USB to PC1, then use the Line-In of the AG03 to connect PC2.


I’m sure it’s not the best solution, but I have an Ground Loop Noise Isolator arriving tomorrow. I bought it last week after posting on reddit and not getting any replies, not sure if the HD 400 is a better version of the same thing or something else entirely, or even if what I bought is just a placebo device.

Anyways. if that doesn’t do anything I’ll give the mixer or HD400 a go.
Thanks for the help! I’ll post back how the isolator goes.

Likely the same thing with different inputs and outputs.

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It does appear to have been a ground loop. The HD400 ground loop noise isolator eliminated almost all noise in one direction, so I ordered another for the opposite. Thank you both for the help!

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