It’s important I think to consider that the pre-amp is just one half of the pairing that makes the whole amplifier. This applies to the S1 just as much as any other Naim pre-amp.
I wrote the following some years back with regard to Naim pre-amplifiers. I’ll post it here as, although it pre-dated the S1, it’s still pertinent and may help provide some answer to the question of what is the S1 pre-amp doing.
So, why have a preamplifier at all? Surely, the best preamplifier is to have none at all?” While it is true that less can often be more, it’s also the case that in Vereker’s words, “less is sometimes just less”.
The preamplifier is one half of the preamp/power amp partnership, which makes up the whole of the “amplifier”. It is separated from the power amplifier to ensure that the electromagnetic fields from the power amplifier’s transformer do not interfere with the sensitive low-level signals within the preamplifier. This way, the preamp provides an ideal quiet room environment, further isolating the low level signals from the effects of microphonics, and ensuring that power supplies are kept well away where they can provide benefit without doing harm.
The preamp has a whole set of complex and vital tasks to perform; the input circuitry must accept the entire output of the chosen source without overload; the frequency response and level of the input signals must be normalised; the preamplifer then conditions the signal to ensure that the power amplifier is driven within its optimum operating parameters. On the latter point, Naim have traditionally taken the route of “bandwidth limiting” the signal, to ensure that ultrasonic signals do not upset or limit amplifier performance.
All Naim’s preamplifiers, from the first NAC12 of 1974 right up to the current flagship of the range, the NAC552, have been designed to have a frequency response flat to within +/- 1dB between the critical 20Hz -20kHz audio frequency range and to offer “perfect stability under all working conditions”.
When designing the first Naim preamp, Vereker saw switched filters, loudness and tone controls as unnecessary impediments to good sound. He felt that their inclusion could never improve the quality of the original signal and always resulted in a loss of information. Instead he looked to design something with excellent stability, high overload margins (over 7 volts!) and with outstanding handling of music transients. The phono circuit had a linear first stage with relatively low gain, followed by RIAA equalisation which was split into two parts, active and passive. This way, complete theoretical and practical stability was attained, with a much wider open loop bandwidth than usual. Exceptional overload capability was thus maintained right across the entire audio frequency range.
