XFX nForce 780i SLI

Audio Performance

The audio performance tests were done using Audio Rightmark 6.0.5 and a 3.5mm gold plated, oxygen free stereo loop back cable between stereo out and microphone input. Results were taken at the DVD sample rate of 16-bit/48KHz and High Definition 24-bit/96KHz.

What we're looking for:

• Noise Level: A higher negative is better. This is usually viewed in relation to a signal level which provides a signal to noise ratio. As you get closer to zero there's more noise and lesser audio fidelity.
  
• Frequency Response: Two values listing how close to the lower higher frequencies the codec can reach. If it hits them perfectly it'll display a 0, 0.
  
• Dynamic Range: The difference between the loudest and quietest sounds the codec can make before it distorts them. The larger the gap, the better.
  
• THD and IMD percentage: Closer to zero is better. THD and IMD are best looked at together because if you have a lot of THD and not much IMD, then it'll offer a warmer accurate sound. High THD and IMD provides a warm, inaccurate sound, low THD and high IMD gives a cold inaccurate sound and finally low THD and IMD gives a cold accurate sound.
  
• IMD = intermodulation distortion and is a fancy way of saying conversion interpolation, which is a basic detection of the quality loss after an analogue to digital then digital to analogue conversion. By comparing it to a highly compressed source it shows up problems with the codec and converters.
  
• THD = total harmonic distortion, which shows up unwanted harmonics; integer multiples of the original component sound that can be second, third, fourth degrees or overtones for example.
  
• Stereo Crosstalk: where the stereo channels "talk" to each other and interact. Ideally you want them entirely separate, unmixed or echoed in either channel, so a higher negative a result as possible is preferred.

16-bit / 48KHz

24-bit / 96KHz

Both nForce reference designs use the Realtek ALC885 premium High-Definition audio codec which supports "protected content" that allows "full-rate audio enjoyment from DVD audio, Blu-ray DVD, or HD DVD discs". In comparison the Abit IX38 Quad GT uses the more popular 7.1 plus an additional 2 channel ALC888 codec. The ADCs and DACs on the ALC885 are rated at a higher performance than the ALC888.

We found that over 50 percent speaker output volume caused quite serious distortion and clipping in the audio stream for both Nvidia nForce motherboards - we had to compensate this by balancing microphone input with a medium speaker output to get the best results. On the other hand, the Abit IX38 Quad GT also uses a Realtek chipset and could set a much higher speaker output volume without such problems, and use a minimal microphone volume to minimise noise.

Despite this difference in setup, the quality from all was very even throughout our testing.