On this page you can find frequently asked questions on audio interfaces.
- Unbalanced, balanced or auto-balanced?
- What is stacking?
- Which level, -10dB or +4dB?
- What is Phantom Powering?
- Whats the difference between Coaxial and Optical S/PDIF?
- Does 96kHz sound better?
- Is the quality of converters important?
- How high should the signal-to-noise ratio be?
Unbalanced, balanced or auto-balanced?
All single channel electrical signals are unbalanced and travel down a single piece of wire (plus ground). A balanced line uses two wires, with the original signal going down one and a mirror image going down the other which has been phase reversed. When the phase is reversed back at the other end and the two signals are combined, any interference picked up in the cable is cancelled out. Auto-balanced cables switch between being balanced or unbalanced depending on whats attached.
What is stacking?
Combining two or more interfaces of the same make and type to expand the number of connections available. Drivers must support this in order for it to work, and not all do. Audio interfaces from different manufacturers cannot be stacked in this fashion.
Which level, -10dB or +4dB?
Ultimately it depends on the equipment. +4dB is hotter and so has more level than -10dB, and on output this could cause distortion through the amplifier. On the other hand 10dB can be too quiet and waste some of the resolution of your dynamic processors. Most interfaces can be switched between the two, so that you can find the idea level for your particular environment.
What is Phantom Powering?
This is usually 48V of power that is required to run a condenser microphone. It is sent back down the same cable as the audio signal arrives on, requiring no separate connection, hence phantom.
Whats the difference between Coaxial and Optical S/PDIF?
Coax cables are highly insulated electrical cables, where the signal line runs down the centre of the shielding antenna cables are coaxial. Optical cables use light that is transferred down a fibre optic cable. Both cables are suitable for digital signal transmissions, although optical is less prone to interference from electrical fields. Coax and optical are not directly compatible with each other and require a conversion box to switch between the two formats.
Does 96kHz sound better?
Although in theory we cannot hear the extra information that is recorded at 96kHz or even higher, it often does sound better, primarily because it allows anti-aliasing filters to be placed at such a high frequency that they have far less detrimental effects on the audio spectrum. There are many other factors that affect audio quality though, so it can only be said as a rule that 96kHz generally sounds a little better than 48kHz on the same audio interface. 96kHz also generates double the amount of data, and so requires the computer to work much harder to cope with the information, and needs double the disk space to store it.
Is the quality of converters important?
Yes, but as with many things, the law of diminishing returns comes into play although as a general rule you will get better quality if you pay more, paying double doesnt double the quality. Unless you have highly trained ears, you may find it hard to detect any difference as you go further and further up the price range.
How high should the signal-to-noise ratio be?
Naturally, in principle, as high as possible. However, the higher you go, the harder it becomes to notice the difference. The maximum SNR for CD is 96dB and thats pretty quiet. To make use of any SNR above 96dB youd need to be working in 24bit resolution, which is one of the advantages of working at resolutions higher than 16bit.