As I am very knew to the audio world, could you perhaps explain to me why these preamps make better sound than an internal RIAA preamp? Is the difference big?
A quick disclaimer, my figures are based off a Google search.
The need for a phono preamp:
Signal levels for a phono output will range between 0.0002 Volt and 0.007 Volt.
The standard CD-player output voltage is 2V RMS, with units varying between 1.74V on the low side and a whopping 7.2V on the high side.
Job 1 of a phono preamp is to amplify the very small phono output to be around the 2V RMS of a CD player to have adequate volume when sending the signal to the amplifier. The phono preamp should do this without introducing noise or distortion to the signal.
Job 2 of a phono preamp is to apply the RIAA EQ curve to the phono signal, ensuring that your records sound balanced and accurate.
The RIAA EQ curve boosts the bass and treble frequencies to compensate for the inherent roll-off of these frequencies that occurs during the recording and playback process.
The better the cartridge the better the phono preamp should be to get the most out of the cartridge. It all depends how picky" you want to be when you listen to records. I'm sure an internal phono preamp can be quite good depending on who is making it and what their standards are.