“What About Signal-To-Noise Ratio”? You may have heard a term called ‘signal-to-noise ratio’. This simply refers to the level of background noise compared to the level of the actual (direct) signal you are trying to sample. Basically, no matter what analogue source you record from, you will experience an amount of background hiss that stems from the components used in the sound source, as well as from the audio cables you use and also from the actual interface.
As you increase the REC LEVEL on your interface, you do not only increase the level of the sound you want to sample (the ‘direct’ sound), you also increase its background noise level. Hence it is important that you achieve the loudest sound possible from the incoming sound source – typically by increasing the output volume of the sound
source. Unfortunately, many CD players do not feature such a volume control, so you have to make do with the volume given to you.
To help decrease the background noise, you should use high quality audio cables and if your equipment has digital outputs you can increase recording quality further by recording via your interface digital inputs using a suitable digital cable.
You may think that trying to amplify the CD level before it gets to the interface would be a solution – of course this would involve the introduction of a third piece of audio equipment into the chain, which, just like the REC GAIN, will just increase the inherent noise level. So, if your sound source has no volume control, you have to make do with the REC GAIN to increase the recording levels to peak. (Of course, your sound source may be quite loud, so you may not need to increase the REC GAIN at all).
If your sound source does have a volume control, use it wisely as there will probably be a point where the units own signal-to-noise level starts to increase – use your ears and listen for excessive increases in hiss.
What if your sound source is so loud that no matter what settings you use (both interface and sound source), the level meter still distorts? In this case, you have to decrease the volume of the sound source by placing a mixer between the sound source and the interface record ins. You can then use the mixers volume controls to decrease the overall signal volume. When reducing signal levels, you’ll find the problem of background hiss is also reduced somewhat.