I happened to have two Naim PSU / preamp pairs open recently and thought it might be a useful record to share the differences. I hope I have the details correct but welcome any corrections!
The first is the SNAPS power supply with the NAC 32 amplifier. These two are earlier than the pair below, and both have the “chrome bumper” The SNAPS has a double 24v output rail each driven by separate LM317 voltage regulators, from a common transformer / smoothing capacitor. It’s only a half depth unit, and has the audio connectivity that allows the audio signal from the pre-amp to feed through the PSU out to the power amplifier.
The NAC 32 pre amplifier has the following cards in it:
NA 325 output delay relay, to protect the power amplifier as the pre amp switches on
NA 322 phono input amplifiers (the 322 is for moving magnet and the 323 is for moving coil)
NA 324 these are buffer cards, I think two for the selected input and two for the tape output
NA 321 pre-amplifier gain boards
The second is the HiCAP power supply with the NAC 72 pre amplifier. This dates later than the SNAPS/NAC 32. The HiCAP is full depth in size and has a beast of a transformer and smoothing capacitors. There are again two separate 24 volt supply rails, but this time they are driven by separate coils on the transformer and separate smoothing capacitors, keeping them more independent from each other. The voltage regulator chip is the same (LM317) but in a different package. There is again the audio feed to link between the pre and power amplifiers.
The NAC 72 preamplifier has the following cards in it (some of which are a later version):
NA325 output delay relay, to protect the power amplifier as the pre amp switches on
NA 322 phono input amplifiers (the 322 is for moving magnet and the 323 is for moving coil)
NA 324 these are pre amp buffer cards, I think for the tape output
NA 729 these are upgraded input buffer cards that replace the NA 324 in the NAC 32
NA 321 pre-amplifier gain boards
