nForce APU

Click on Start, Settings, Control Panel then NVIDIA nForce Control Panel & select the Speaker Setup tab.

Listening mode. From the drop-down menu here select the speaker system you are connecting to as appropriate (Or the closest available option), e.g. if you have the MegaWorks 510D then select 6 Speakers. 

Analog Output. Tick this option should you be using the nForce's analog outputs to connect to your speaker system. This would be the most appropriate should you lack a Dolby Digital decoder to connect to or your nForce motherboard lacks the DICE (Dolby Interactive Content Encoder). Should you only wish to use the S/PDIF Output then leave this Unticked.

Digital Output. Tick this option to enable the S/PDIF Output of your nForce, which will output audio at 24-Bit, 48kHz. This will provide improved audio quality over analog output given the generally superior DACs that will be using in receivers/decoders. This is also required should you wish to use the DICE feature of your nForce. Should you not have a receiver/decoder to connect to then Untick this option.

Dolby Surround Encoding. Available when using Analog Output, Dolby Surround is comprised of front left/right channels & an additional mono channel used for rear left/right output albeit with a limited frequency range of 100Hz - 7kHz. This extra channel is outputted with a regular 2 channel stereo signal & will only be decoded when connected to a compatible decoder. On other systems only the stereo channel will be outputted. As with most up-mixing technologies it would be best to leave this disabled (Unticked) to ensure optimal audio quality when using analog output, unless perhaps where you actually can connect to a Dolby Surround decoder.

Dolby Digital Encoding. Tick this options should you wish to have the nForce encode audio into a 640kbps Dolby Digital stream. This is of course highly recommended should you be connected to a Dolby Digital decoder via the S/PDIF Output. This will provide improved audio quality over the analog output in most instances (Presuming the decoder features better DACs, which is likely). I would however recommend that you disable (Untick) this when not playing multi-channel audio, such as CDs or MP3s, as Dolby Digital is a lossy audio format & this way you can retain the full quality of such sources, whereas for DirectSound 3D supporting games Dolby Digital encoding should have no noticeable effect on quality giving the generally lower quality sources used. This also is not required should you by sending an AC-3/DTS stream to your decoder either, e.g. via a software DVD decoder.

Create Center Channel. When Ticked this will generate a center channel from non-3D positioned stereo/mono sources. This is of course only recommended should you desire such sources, e.g. CD/MP3 played through that channel in addition to the others. As with most sort of up-mixing features however I'd not particularly recommend this & would leave it Unticked.

Center Channel 3D Pan. When Ticked this enables audio to be positioned & output through the center channel in DirectSound 3D supporting applications/games. You should only Untick this should you not be using a 5.1 speaker system. On 5.1 systems this will allow for improved 3D positioning as sources can be played through the front center channel where appropriate.

Create LFE Channel. Tick this option to enable the redirection of bass content to a Subwoofer which requires a separate input, e.g. Videologic DigiTheatre LC, otherwise you will not be able to get any Subwoofer output on such systems (Bar that of the LFE channel). On other speaker systems you can leave this Unticked without issue (As they can create their own Subwoofer content using on-board bass management), though should you have no subwoofer output currently then try enabling this to see if it fixes your problem. This feature can be further customized using the LFE Crossover Frequency option.

Rear Speaker Phase Shift. Should you find your rear speakers playing audio incorrectly or unusually distorted then try Ticking this to solve the problem, otherwise you may leave this Unticked.

LFE Crossover Frequency. With Create LFE Channel enabled this option allows you to adjust the crossover frequency (50 - 500Hz) to be used, beneath which, such low frequencies will be directed to the Subwoofer. Increasing this value will result in a stronger bass output from the Subwoofer & vice versa. NOTE - Be sure to check your Subwoofers specifications to see what frequencies it can handle also so that you don't set this too low or (more importantly) too high.

Premix Volume Levels. Adjust these sliders to your own preference.

Now select the Main tab.

Equalizer. The equalizer allows you to adjust the level of amplification for various of frequency ranges - comprising the Bass (20Hz - 250Hz), Mid (250Hz - 6kHz) & Treble (6kHz - 20kHz) ranges, thus allowing far greater tuning capabilities. Adjusting these frequencies can improve audio quality for some sources; although this is largely dependant on the source itself (Some may benefit from more bass, others treble, etc.) & your own tastes. Should you want to adjust these levels then Tick then Enable button.

Input. You can basically ignore these option unless you'll be recording audio with the Soundcard, in which case select the appropriate source(s) from the drop-down menu. For optimal performance you should set the Digitized Input to Off as well.

Output. Use the Master slider bar to set the global volume level for Audio output. Move this slider to Up to increase the global volume level & vice versa. It is generally recommended that you set these to 70% or thereabouts if you intend to adjust the Equalizer levels, this will reduce the amount of amplification the Soundcard can apply to a source, which could cause audio artefacts at higher levels. Although should you not intend to be adjust the Equalizer levels then you should be able to increase the volume level to a much greater level without compromising quality. These other sliders can be used to adjust the volume level of different audio sources, moving a slider Up will increase the volume level of said source & vice versa. I'd also recommend Ticking the Mute button for any unused sources as well.