If you have a turntable that you play your vinyl records on and would like to connect it to your PC or Mac, perhaps to archive or transfer your records to CD or MP3 then a you will need a phono preamp. This is connected in-between the turntable and computer to ‘match’ the two pieces of equipment together. Without a phono preamp practically nothing will be recorded or heard.
Here is a quick explanation of what the phono preamp does.
The output from a standard turntable is very low – in fact in the region of a few millivolts (one millivolt = one thousandths of a volt). Now the ‘line in’ input of your computer requires a much higher level than this (somewhere in the region of 300 millivolts) and should the two be connected directly together the result would be practically no volume at all.
So – the first thing a preamp does is increase the level coming out the turntable and pre-amplify to a level more suited to the ‘Line In’ on your computer. That’s the job of a pre amp – to increase signal levels or amplify.
A phono preamp must also change the ‘character’ of the sound and acts a bit like the ‘bass’ and ‘treble’ controls on your hifi. It’s designed to do this to compensate for inadequacies in the manufacturing process of vinyl records. When records are produced ie ‘pressed’ it’s not possible to ‘encode’ in the records grooves very much bass, but does however ‘encode’ an awful lot of treble! – so a phono preamp must increase the bass and reduce the treble by a set amount (which is laid down by an organisation called the RIAA) so the sound we hear approaches as near the quality of the original recording as possible. Without the phono preamp all we would hear would be a very low volume, scratchy, tinny, noise. Very unpleasant!
Hope this has helped : )
Phono preamps come in all ‘shapes and sizes’ so here are a few reviews and explanations of the various types.