Go to ‘Audio’ and drag the slider almost all the way to the left (1).
Do not change the system volume after this, you should only control the volume either from within your media player or on your hardware sound system. Turn up the system output volume all the way to the maximum.
#External sound card for mac os x install
This is the kind of account that allows to install stuff. Log in using an administrator account.Setting up a Multi-channel Sound Card: the Procedure You can also use the decoder with any other hardware device that has an optical output. This will be much less hassle, you do not need to go through the steps below, it will work in more media players, and it will avoid bugs in the few media players that do support multi-channel sound cards.
#External sound card for mac os x Pc
To be honest, if you are serious about hooking up your Mac or PC to a surround sound system, I recommend the pass-through method: buy a standalone 5.1 decoder, connect it through an optical cable (with a 3.5mm jack adaptor if needed), and set up your media player to pass through the AC3 or DTS stream. Right up to the point where it is decoded in the receiver, this stream looks like, and is treated as, an ordinary stereo stream. You do not need to bother about Audio Midi Setup when you pass through the encoded stream. The instructions below are unnecessary for the pass-through method.
It should then only depend on the receiving device whether it is capable of decoding the stream or not. If you can change the volume, you must set it to 100%.
To make this work, all you need to do is force your media player to pass through the encoded stream, and ensure that the outgoing ‘audio’ is not altered by a volume control or anything else. With the advent of HDMI, it has become possible and common to send the stream over the HDMI cable. The most popular way to send the AC3 or DTS stream to external decoders used to be over an optical cable, often called S/PDIF or TOSLink. The second way is to keep the undecoded surround stream intact and pass it through to a smarter external device like a surround receiver, which then does the decoding to its six (or more) outputs. The most popular standards for encoding 5.1 audio in a bitstream of 1.5 Mbit or less are Dolby Digital (AC3) and DTS. A decoder that does not recognise the encoding will output a terrible noise because that is what one gets when trying to treat compressed data as PCM sound. Instead of treating it as stereo sound, it interprets it as digital data and decodes it, just like an MP3 player decodes the compressed data in an MP3 file. A surround-capable decoder recognises this special stream. Because the transmission is all digital, there is no risk of degradation that could destroy the information in the compressed data.
The compressed stream is then transmitted as if it were a regular stereo stream. The trick is to compress the six separate channels into a bitstream that is not larger than an uncompressed (so-called PCM) stereo stream of about 1.5 Mbit/s. For many years, digital 5.1 surround has actually been a bit of a clever hack of the existing S/PDIF standard that only supported uncompressed stereo audio.
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