I worked around my soundcard interference problem

2004-01-05 14:40:58

For quite some time, I've had a problem with audible interference problems on my M-Audio Audiophile 2496. Since I had been unsuccesful in solving it with the standard procedures (removing other cards, muting inputs, etc.), I was already thinking about buying a USB card (and posted some inquiries about it on this board).

Before doing this, I decided to have one last troubleshooting session, and lo and behold, I managed to solve it.

However, the solution surprised me, and also disappointed me.

First a word about my system. Besides my Audiophile 2496, I also have an onboard soundchip (SoundMAX) on my mainboard (Asus P4PE). This onboard chip is set as the default Windows sound device, so all "garbage" like Windows sounds, application sounds and Flash sounds get sent to it. This way, I can listen to music on my Audiophile 2496 without being disturbed by systems sounds.

Both sound cards are connected to a Yamaha AX-590 amp (one at the "CD" input and one at the "Aux" input), and my Sennheiser HD535 is connected to this amp.

After trying many things, I noticed that the interference goes away when I disconnect my onboard SoundMAX from the Yamaha amp. I found out that I have no interference when I have only one card connected to the amp (and use e.g. a separate headphone for the other card). I got my first "hint" at this when I did RMAA measurements of my Audiophile 2496 in loopback mode, while the SoundMAX was still connected to the amp. I was surprised that I got excellent results, and a low noise floor in this setup (I expected a high noise floor with all the interference I heard).

Now my question is: how do I properly solve this? I only see three possibilities, but neither are satisfactory for me:

1. Permanently disconnect the SoundMAX from the amp. This is unacceptable, because I do need it every now and then (e.g. for gaming).
2. Change connections (e.g. disconnect one card and connect the other) when I want to use a different card. This is way inconvenient, and I'm not happy with this.
3. Use a separate headphone directly connected to the SoundMAX. This is also inconvenient, because I need to keep two headphones at my desk. And I also have a pair of bookshelf speakers (B&W 602)connected to the amp, which I won't be able to use with my SoundMAX.

Does anybody have a suggestion for me? What can I do to keep both cards connected to my amp without the interference? Also, can anybody explain to me why the amp makes such a difference? I mean, when one of the cards is disconnected from the amp, it is still active inside the PC, isn't it? So why does it only cause interference when connected to the amp?

I really hope anybody of you can help me with my problem. Many thanks in advance.