Firstly a word of caution. If you are replacing the feet on the 160, which is a good idea on a product of this age, be aware that the earth strap connects to the chassis through the bolt attaching the foot closest to the mains input socket. I didn't realise this and removed and replaced the foot leaving the earth strap and nut floating around inside the case. Luckily I spotted the error before any damage was done.
Serial number 0492 dates your 160 to the second half of 1976.
The NAC12 is an excellent and under-rated pre-amplifier. The weakest points are the basic quality controls. You owe to yourself to replace the volume control with an Alps Blue (
http://uk.farnell.com/alps/rk27111220k/potentiometer-20k/dp/1191722?Ntt=1191722) or better. If you don't need the balance control, replace it with two fixed resistors. If you do need it, find a better potentiometer. I also replaced all the sockets on the rear panel.
There are three versions of the 12. Version 1 has all the components on a single board (with the possible exception of the phono boards) like the NAC42, Version 2 has six daughter boards (2 x 324, 2 x 321 and 2 x phono (322 or 323)) with the relay circuit on the motherboard. Version 3 also has the relay circuit on a 325 daughter board making seven in all.
Versions 2 and 3 are very little different to the NAC32. The performance can be further improved by replacing the 324 boards with the 729s as fitted to the NAC72.
You will probably find that the tantalum beads are all rated at 25 V, Naim had a program of replacing these with the 35 V types when units came in for service.
I have a future project to fit individual regulators for each board. The layout makes this extremely simple. A strip of regulators would easily fit onto a side panel and you could feed in 37 Vdc or so from a printer brick or, alternatively, you could wire out the pre-amp regulator in the 160 to get a similar raw dc supply.
malcolm
p.s. Having checked I remember that the NAC12 Version 2 has different edge connectors to those used in the later preamps so more modern boards will not fit. The Version 3 has the same edge connectors as the NAC32 - NAC72 and is, therefore, somewhat easier to upgrade.