Weird Audio Problem with DVI Extender

I posted a thread on my configuration that I set up for extending my PC display and USB over ethernet here. The final configuration is in the post dated 11-02-11. The two devices I'm using are:

- NTI DVI Extender with Stereo Audio
- Icron USB 2.0 Ranger 2204 - 4 port USB 2.0 Cat5 Extender

Have come across an audio issue with my setup I listed in the thread, and am at wits end on where the problem could be.

If I connect the stereo audio port on my DVI extender to the on board audio on my motherboard, no issues. Sound is very clear and clean.

However, I also have an external USB sound card, an RME Babyface which looks like this. As soon as I connect the DVI audio to the RME sound card, I heard buzzing, almost like it isn't grounded properly.

The strange thing is that the buzzing corresponds with PC processing activity, not sure if its CPU, memory, or video card activity. Every time I load a program, or run a program that requires some processing load, the sound buzzes, pops, and clicks almost like I have an ear to the motherboard as it's working. If I have absolutely nothing running, it's almost quiet.

I've tried:

- Different audio cables & connectors
- Different audio ports on the USB sound card
- Connecting the USB sound card to different USB ports on the PC

Again, this is ONLY when using the USB sound card. The onboard motherboard sound card does not have this problem, so it can't be an issue with the DVI extender.

I've already talked to NTI support about this and they have no clue what could be causing this.

Kind of a long shot posting here, since it's not exactly a common setup, but there are a lot of wizards on this site so thought I'd try. Any ideas?

Thanks for the replys guys, responses below:


Yes, I have all audio routing through the USB sound card. I've even disabled the onboard motherboard sound.


1. Connecting direct is fine, either through headphones or speakers. The problem is only when connecting either the headphone or speaker outputs on the USB sound card to the stereo audio input on the DVI extender.

2. The RME Babyface is a high end sound card for music production and has a great deal of horsepower that the onboard motherboard sound card doesn't. Need it for composition tools that load up large soundbanks and perform with low latency.

Normally I would assume that it would have been a low signal as well, or possibly cross connect somewhere. However, the fact that it seems to be amplifying activity on my PC's CPU or other processing just bewilders me. It has to be picking up something through it's USB connection to the PC, but why? And why only when I send the sound on through the DVI extender? Maybe the DVI video connection in combination with the stereo connection to the DVI box is completing a circuit of some sort?

Yes, have tried those too. The sound card comes with both balanced and unbalanced XLR speaker connections. I picked up a few adapters to get the output from the balanced XLR connections to the stereo mini-jack on the DVI extender. I verified specifically with the rep from the store that the adapters were balanced. I could try the unbalanced XLR connections, but the headphone output on the card is also unbalanced (I believe) and I have the buzzing problem there too.

In the case of the headphone output, which is the connection configuration I mostly use, it's just a straight stereo audio cable. The headphone output on the USB sound card is a 1/4" TRS jack. The stereo input on the DVI extender is a stereo 3.5mm input. The audio cable is 1/4" on each end, so I also use a 1/4" to 3.5mm adapter to plug into the DVI extender.

I don't have the XLR adapter set up in front of me here, but I get the same identical issue whether I go through the headphone output or the XLR output, so don't believe it would be an adapter issue.

I'll take a couple of pics of the set up and post them later today.

So here are a few images of my configuration, fairly simple. Images attached are:

1. The stereo adapters I have connected to the USB sound card.

2. Connection to the headphones output of the RME sound card.

3. The stereo cable is about 3 feet long, and is connect to the audio input of the local DVI device.

4. Audio output on the remote DVI device. Again, just a mini stero jack.

What I didn't show is the USB connection to the PC, but this is just a straight USB 2.0 cable to a USB port on PC motherboard. Again, I've tried other USB ports on the motherboard and no difference.

Also forgot to mention. I've tried moving the RME sound card farther away from the PC or other power sources, no effect.

Yes, normally I would assume this would have been a grounding issue. However, the buzzing is not a continual unwavering buzz that you would normally hear with grounding problems. In this case, the sound seems to buzz, pop, and click in sequence with cpu processing. Everytime I load a program, or the cpu is doing some work, the sound starts jumping around all over the place. It actually sounds more similar to the old dial up modem sounds.

Nope, the card is fine. Perfect sound when I connect either headphones direct to the card or to the speaker outputs. It's only when going through the DVI extender that there's a problem.

It's connected to a normal USB port directly on the motherboard, nothing done internally. Haven't actually heard of doing an internal USB connection, is that something wired manually or is there a port right on the circuit board?

I had wondered about that too. However, the RME sound card also comes with a separate power supply, which I tried, but didn't solve the problem.

Side note, I just tried disconnecting the DVI video cable from my PC and the buzzing disappears. So it's definitely something cause by both the DVI video and USB audio connecting to the DVI extender. Again, if I connect the audio to the onboard motherboard sound, there is no buzzing. It's only with the USB sound card.

Ok I see now, thanks for the info. My PC is wired with the front panel USB ports, and I've confirmed that they're wired directly to the MB. However, I've tried these USB ports as well and no difference. I also tried the USB 3.0 ports.

Yes, have tried the dual port USB cable. Actually normally have it connected with both USB ports for the extra power. Have also tried the dual USB connections on the two front USB ports, which would be the internal USB connections, from the info that @ljo000 sent.

Damn him! Not again !