Question

Explain the function of the pre-amplifier in detail.

Answer 1

experience with naim gear is that the preamp is where most bang for the buck is realized, although undressing the source is not a good idea. Whether this is the same with other brands, I dunno, but reducing the importance of a preamp to a selector and an attenuator is a simplification that serves too little justice to what goes on in a proper preamp.

Besides attenuation and input selection the pre also process the signal and decouples the load on the source from the power amp. This may seem unessential, but instead of just thinking simpler is better and the shorter the signal path, the better, one also has to considder that different duties have to be separated to process them the best. A clear example of this is in poweramps that needs to ad gain (voltage) and offer the needed current with as little modulation as possible to drive the speakers. Most poweramps does this in stages and separates the gain stages (voltage gain) from the current delivery to the speakers (output transistors) to minimize the effect of the modulation in the current delivery stage on the gain stages, as these stages multiplies not just signal but also distortion artefacts. The preamp thus has to do the same basic function hence the need for it and its plural stages to minimize modulation in one stage reaching other stages like gain stages, or the output stages of the source. On top of that, (most) naim preamps include timealignment circuitry to process the signal before the gain stages. Every stage then preferably needs a dedicated and regulated powersupply which essentially is what increase complexity and cost, as one moves up the ladder of naim preamps, and pweramps for that matter...