Issues with mix-minus setup on Xenyx Q1002USB with dbx 286s

Question

My setup is simple and complicated at the same time:

My mixer is a Behringer Xenyx Q1002 USB Premium. 1. I have a XLR microphone going into a dbx 286s Mic Preamp/Processor. The processed audio is output through a 1/4" to 1/8" cable, with a 1/8" adapter into the mixer on line 1.

2. My PC audio goes out of the motherboard, leading via 1/8" to 1/4" cable to the mixer on lines 5/6.

3. I have another 1/8" to 1/4" cable leading from the back of a TV into the mixer on lines 9/10 for whenever an HDMI device is connected to the TV.

4. I have a 1/8" to 1/4" cable going out of the FX Send into the PC. (Line 1 has FX send turned on so I can have the isolated microphone audio available for recording)

5. I have a pair of headphones connected to the Phones Out for monitoring.

This setup would allow me to have PC and TV sound coming in through the headphones, as well as monitoring for the mic.

The problem is as such:

I used to run 1/8" to 2x 1/4" unbalanced audio cables from the PC and TV into the mixer, but with the addition of the dbx 286s, it generated lots of noise that appeared to be coming off of lines 5/6 and 9/10, with the microphone appearing to be in perfect quality on the monitoring headphones and on recordings on the PC.

I suspected that this might be a ground loop issue or interference from the equipment, since the unbalanced cables are susceptible to it. I replaced the unbalanced cables with 1/8" to 1/4" cables, thinking that would fix it.

However, now the fidelity of the sound is ruined. Particular frequencies play at regular volume, while others are extremely low or mute. Spoken word is muffled and music can barely be heard, except for particular instances where it pops in and out for a split second. Different programs seem to have different reactions, as music being played through foobar2000 seems to not be effected as much.

My question now is, is there something I could do to either:

a. Make the setup work with the new balanced audio cables and restore the fidelity of the audio.

b. Change the setup in a way that the 1/8" to 2x 1/4" unbalanced audio cables will work and not generate noise in monitoring.

The spare parts I currently have are a male XLR to 1/4" cable, the two 1/8" to 2x 1/4" unbalanced audio cables, a female XLR to 1/8" cable and USB cords that can connect the mixer to the PC via USB. A ground loop isolator is also in transit and should be delivered in about a week, so I can work that in potentially.

Answer 1

a. Make the setup work with the new balanced audio cables and restore the fidelity of the audio.

You don’t have new balanced audio; you have unbalanced stereo going into a balanced input which does not work and is why the audio sounds horrible and like things are missing. (Because they are.)

b. Change the setup in a way that the 1/8" to 2x 1/4" unbalanced audio cables will work and not generate noise in monitoring.

If it is the preamp that introduces the buzz try to plug all the equipment into the same power strip. Do you have a device plugged into a different outlet across the room? Also try to connect a DI box between the preamp and the Behringer and lift the ground switch of the DI.

Answer 2

I replaced the unbalanced cables with 1/8" to 1/4" cables, thinking that would fix it.

That's still an unbalanced cable. Your PC output is unbalanced, any cable connected to it will be unbalanced.

You could insert a DI between the PC output and the mixer. Use a passive DI or an active DI with a power supply. Experiment with the Ground lift switch.

However, now the fidelity of the sound is ruined.

It is possible that one of the jacks is not fully inserted. I can create this effect by pulling a 1/8" jack from its socket by just the right amount.