Madge
13-11-2003, 01:35 PM
3 different cables, 3 identical connectors, 3 wildly differing uses. One thing in common.
All are designed around a 75 Ohm impedance in the consumer world.
When is a 75 Ohm interconnect not a 75 Ohm interconnect?
Well, the impedance of any cable is complex. It is not a fixed value for all frequencies.
Hence the differences between digital audio and analogue video cables - the intended impedance covers the bandwidth for that type of signal. Outside of this bandwidth the impedance can change quite dramatically.
Any variation from these specifications can cause audio/video noise, which depending on the resolving system can be very noticeable.
Analogue audio cables are an even trickier area. Quite often they are nowhere near 75Ohms over the audio bandwidth, except possibly at the lowest frequencies. Manufacturers can design or experiment in different behaviour within the audio band, to give a more pleasing or detailed sound - a nominally flat 75 Ohms throughout the audio band can sound quite harsh and over detailed. It is even possible to add 'air' to instruments by using a high impedance plug at the pre-amp end and a low impedance plug at the power end.
All are designed around a 75 Ohm impedance in the consumer world.
When is a 75 Ohm interconnect not a 75 Ohm interconnect?
Well, the impedance of any cable is complex. It is not a fixed value for all frequencies.
Hence the differences between digital audio and analogue video cables - the intended impedance covers the bandwidth for that type of signal. Outside of this bandwidth the impedance can change quite dramatically.
Any variation from these specifications can cause audio/video noise, which depending on the resolving system can be very noticeable.
Analogue audio cables are an even trickier area. Quite often they are nowhere near 75Ohms over the audio bandwidth, except possibly at the lowest frequencies. Manufacturers can design or experiment in different behaviour within the audio band, to give a more pleasing or detailed sound - a nominally flat 75 Ohms throughout the audio band can sound quite harsh and over detailed. It is even possible to add 'air' to instruments by using a high impedance plug at the pre-amp end and a low impedance plug at the power end.