An introduction to computer audio
Connecting your computer to your audio.
There are many ways to connect your PC to your amplifier.
Analogue
Headphone out to line in.
This is a very cheap solution, a Y-cable will do the job.
Probably not the best way as you might have a mismatch between the two in signal level. Be careful with the volume control.
Sound quality probably moderate.
This is excellent to start with, you can try your hand on computer based audio without getting your feet wet.
Sound card line out to line in.
The sound card does the digital to analogue conversion (DAC) and amplification
to line level. A standard audio cable with RCA connectors will do the job.
Sound quality depends on the quality of the sound card.
The name "RCA" derives from the Radio Corporation of America, which introduced the design by the early 1940s to allow mono phonograph players to be connected to amplifiers.
XLR
Balanced connections are the prosumer standard for decades.
The whole trick is the sender puts the signal on one lead and the inverse on the other.
The receiver checks the two signals and removes any differences between the two.
This is the way to go if you run long cables in a electromagnetically noisy environment.
More en more consumer products feature XLR.
A lot of sources are single ended by design so you need a balun to create balanced output. Likewise at the receiver you need a differential amp or a transformer.
You might ask your self if adding a balun, a differential amp or a transformer to the signal path is a improvement in sound quality.
Digital
The standard to connect two audio components ‘digital’ is based on the S/PDIF protocol.
It can be done optical (Toslink) or electrical (coax).
Toslink
Toslink cables are made of plastic or glass. The plastic ones are cheaper but might have higher attenuation coefficients (1 dB/m or higher). Range probably limited to 5 - 10 meters but might be less if the signal is weak.
Sometimes a headphone out doubles as an optical out (Apple, Toshiba). In this case you must use a mini-Toslink.
Toshiba created TOSLINK (1983) to connect their CD players to their receivers. It was soon adopted by manufacturers of most CD players. Using light it is immune RFI and EMI and the devices are completely electrically separated.
Coax
Coax cables in general use RCA or BNC connectors. Range can be 10 – 15 meter or even more. The ones equipped with RCA connectors look exactly like a analogue RCA cable but for best results it must be a true 75 ohm cable. A ‘digital’ cable can be used for analogue as well. More about digital cables can be found here.
Then of course you have people who think that you can connect the digital out of a sound card with a RCA Y-splittercable to the analogue in of your amp or active speakers.
Electronics are simple, if you make a mistake the spot is automatically marked with a smoke signal.
A quad shield RG6 (antenna cable) will do the job at a very low price. Some even run S/PDIF over 30 m RG6 with success. Something to keep in mind before you buy a Audioquest Eagle Eye with 72V DBS Digital Cable at $650,- per meter.
XLR
The prosumer standard is AES/EBU. It is a balanced connection using XLR. A 110 ohm cable must be used.
USB
USB-speakers are a well known and popular example.
The computer audio is routed over the USB. As it is a digital signal, it has to be converted to analogue (DAC) before it could be fed into an amplifier.
If you want high quality audio, you need a high quality USB-DAC.
Bluetooth
Bluetooth is a popular way to connect devices wireless. Mouse, keyboard and other peripherals, when connected wireless it is by Bluetooth.
In audio BT is often used to connect a MP3 player and a headset wireless.
Often this is done by plugging a Bluetooth dongle in the headphone out.
In this case, the audio is converted from analogue to digital, send to the receiver and there is converted to analogue again. Not exactly an audiophiles paradise.
Best audio quality is obtained using the A2DP protocol. It support the following Codecs
MPEG-1,2 Audio
MPEG-2,4 AAC
ATRAC (Sony)
In essence high bit rate MP3 but vendors can implement their own protocols.
With a nominal bandwidth of 3 Mbit/s (2.1 + EDR) it is not really suit for high resolution audio.
In general these products are targeting comfort, not high quality sound but maybe this is an exception to this rule.
WiFi
WiFi is used to push the audio from the PC to a receiver.
The music is send to the receiver by WiFi (often a wired connection is supported to) and is converted there to analogue and fed into the stereo.
In principle any format played on your PC can be transmitted without any conversion to the receiver.
Input: ethernet / wireless G
Format: supports every known audio file format, including MP3, WMA, and AAC - even DRM protected files are supported
5.1 channel Dolby Digital surround sound
Output: RCA / Toslink
Wireless video transmitter
One day I stumbled upon this post: http://www.hydrogenaudio.org/forums/index.php?showtopic=40839
A guy connected two audio devices by sending the S/PDIF over a wireless video transmitter.
Protocol converters
You can’t connect two devices if they don’t have the same interface in common.
If your PC has USB out and your receiver S/PDIF in, you can try a USB to S/PDIF converter.