Optical or coaxial, what to choose? :

In the "entry level", ie in very affordable prices, an optical cable has a good chance to be more effective because it is insensitive to electromagnetic interference, in fact the optical link uses the light, however, this process requires more than an RCA coaxial connection, adding a digital converter / optical output of dvd player (internal), a converter and optical / digital input of the amplifier (internal) and these converters have a maximum speed of 6Mhz (minimum) for most, which is sufficient for digital sound samples 48kHz (ie a DVD classic) but enough for a sampling of 96 or 192 kHz (DVD -audio, HD-DVD ...) and sometimes poor quality of these converters can result in distortions of the digital signal containing the flow of DTS or Dolby Digital.
Also note that for a long link (over 10m), it is preferable to use a coaxial connection for the power of light (Toslink transmitter) in this case is too small for larger lengths.

The advantages of the optical link:
- Insensitive to electromagnetic waves
- No transfer of masses (galvanic isolation with opto-electronic elements)
- An optical cable quality is significantly less expensive than coaxial cable RCA quality.

The disadvantages of the optical link:
- Sensitive to dust
- Significant loss factor (hence our advice to limit this type of cable to a length of 10m max)
- Speed limited
- Double conversion necessary
- Somewhat fragile
- Connectors Optical often of poor quality equipment on the entry.

With an RCA coaxial shielded cable of very good quality (OFC copper conductors, Gold plated connectors ...), there is a good chance that the sound quality is better because in this case it does not convert the signal twice, and therefore there is no limitation in speed 6Mhz minimum

The advantages of coaxial RCA connection:
- Flow rate well above the optical link:> 100 Mhz, therefore compatible with high sampling rate (192kHz).
- No galvanic isolation between the player and the amp, so there may be mass transfers.
- Attenuation of signal rather low (around 3 to 30 dB per km).

The disadvantages of the RCA coaxial connection:
- Bounces waves for cables longer than 15m when the connector impedance is 50 Ohms (often the case) instead 75 Ohms.
- Cable quality expensive.

In conclusion?

The optical link is theoretically superior to the coaxial connection but the optical connectors are often of very poor quality, and throughput is limited by the digital / optical and optical / digital coaxial cable can achieve better results in the vast majority of cases, including links lengths over 10m.

Among the best brands of RCA coaxial cables can include Cable Positive (Optimum Libra), QED (QUNEX series), or Audioquest.