TLDR: I get a buzzing and popping noise when either channel is turned down. With both channels maxed out, it works fine. However not entirely sure it's the fault of the device, or something odd in my setup. More details below...My setup is using this to control the audio output from two computers, and merge them together.Computer 1 > USB audio interface > mixer > tube headphone amp > headphones (this computer has a 3090 with noticeable coil whine)computer 2 > mixer > tube headphone amp > headphones (standard computer, noting out of the ordinary)-with the above, I could hear audio but the buzzing/beeping/popping of the coil whine from the 3090 would conduct through the mixer, into the amp, and I would hear it. Very annoying. Would happen in both op-amp and resistive modes-unplug computer 2 (just 1 plugged in), no interference, unplug computer 1, just 2 plugged in, no interference-ran an oscilloscope on line from computer 1, clean. Ran scope on computer 2, saw the interference from the coil whine that was occurring on computer 1 (odd, but can't fault the mixer for that can we?). Figured it was an odd issue with the motherboard audio out on computer 2.-Installed a USB audio interface on computer 2. Ran scope on audio out, no interference-Plugged computer 1 and 2 into the mixer, both at full volume, no interference. Great! Not quite, as soon as I turn down computer 2 with 1 maxed, interference. Turn down computer 1 with 2 maxed, interference. As soon as either computer is turned down (via the mixer), interference comes back.-Run scope again on both line outs from both machines, no interference on either. Figure it had something to do with the power (was running in op-amp mode, power via USB phone charger brick). Disconnect power and run in resistive mode. Same issue-I then think hmm, grounding issue? Disconnect computer 2, keep 1 connected, and connect just the ground from computer 2 to the ground of the mixer (just touched the grounding part of the line out to a bolt/screw on the mixer). Then so long as volume of computer 1 is up, interference. Turn it down, interference goes away. Test the opposite way (computer 2 connected, line in from computer 1 grounded to chassis, same thing)-Scope between grounds of both line ins (computer 1 + 2), no recognizable waveforms but definitely some potential visible. The grounds are not equal, and that's likely causing the issue. However, this imbalance of potential somehow cancels itself out when the volume of both inputs are at the same volume. At this point learn that it doesn't necessarily matter that the volumes are maxed, only that both are identical volume level with the knobs on the mixerSoooo 3 stars. Would it work in a standard situation? Probably. Can I fault the mixer for my GPU having coil whine and that somehow conducting through the mixer? No. Plus, it technically does work for my uses. I wanted to be able to hear both machines from the same set of headphones, and for that it works. I can adjust volume from each machine separately (on the computers themselves), and that works.It's just that it's supposed to be a mixer. Channel 1 being off is not supposed to affect channel 2. They're supposed to be separate. Even in odd circumstances when the grounds of both inputs aren't equal like they should be, the circuitry should be such that it doesn't conduct interference into the final output signal. That problem should be fixed.

I bought this to mix the audio output of two devices in the airplane to feed into my single aux audio port. The two channels have independent input volume controls and there's a master volume output. It was super easy to get the exact volume I wanted for each channel, one a loud O2 system alarm annunciator and the other, a softer bluetooth audio input for the iPad music and foreflight audible alerts.I thought I would need to power the mixer and use it's "Active" mode to boost the inputs but I found that the passive mode (no power required) sounded better. Active mode actually made the sound a bit more tinny and processed.For my application (a noisy aircraft environment feeding into ANR headsets), the sound quality is pretty impressive. I have tried this thing in a quieter environment that might bring out more subtle audio qualities (or issues).

Headphone jack barely works. If the mixer moves slightly, sound cuts out. However this issue is nonexistent if you just use the line out instead. Great sound! Loud volume. Just can’t use the headphone port

I had a lot of issues with it at first but I figured out all the problems I had:- Like explained in the documentation make sure to use a usb power supply with a single port or it will introduce noise- use ONLY TRS audio cables (Stereo WITHOUT mic). TRRS cables (Stereo WITH mic) will introduce noise or humming. I also made sure to get shielded cables. With more than 15 feet of cables the sound remains perfect.

I got this to join an Echo speaker to my computer's sound system, so that I could use said system in Alexa Speaker Groups. I was trying to mix two line level signals into an amplifier that could be turned up for any attenuation by the mixer. This little box works great for that!I had some noise in active mode, which I guess could be due to the power supply I was running the USB power cable from, but I decided to just use passive mode with no USB cable (the noise was still present when 'off' but still plugged in). This made the mixed signal quieter, but a small volume bump on the 2Ch Fosi amplifier it was feeding and it sounds perfect to my average ear.

At the time of this review I've only been testing it for half an hour or so, but theoretically it does exactly what it should. For clarity this review is for the MX3 2-channel variant because I only needed to combine 2 channels.Using it to combine audio streams from the headphone port on a PC, and the aux out from my 32in monitor which is being fed by my HDMI matrix full of consoles. Role was previously filled by a cable that did something similar, but didn't have the dedicated volume controls or volume amp. In my use-case I have the headphones running through the back port to reduce cable clutter, I don't believe you can have BOTH the front and rear headphone ports at the same time, and if I needed 2 sets of headphones I imagine I could just use a splitter down the line. I'll update my review if something changes of course.Things to note; In my initial testing there was some garbled audio, but that can probably be attributed to the old "twist the cable until it cooperates" scenario. I have a limited number of M to M cables, so I can't definitively say the ports on the device aren't a little weird, but once I got all the cables properly routed for longer-term use it stopped acting up. I also have mine plugged into an old iPhone power brick on a power strip on a different wall than all my other devices to try and prevent a ground loop, so far it seems to be working fine.Volume control is smooth, no garble or static when adjusting the dials. Easily able to adjust game and PC volume on the fly, as well as the overall maximum volume independent of my headphones or PC volume. I suggest turning everything down to mid before you give it a listen, because this thing can get LOUD with Youtube/PC/Headphones all being at/near 100%, even with everything set to 75% it's plenty loud enough with room to bump it up if you really needed to. Old cable solution definitely didn't get as loud so this is a definite improvement. There's still some background hum, but if I turn my headset down and everything else up there's no issue.TL:DR it works exactly as advertised as of Day 1. Things get loud, and you can easily decide which input gets to be louder which is the whole point. I'll make an edit if it explodes after the review.