It CAN be done on most Audio Research preamps, but you HAVE to be sure about what you are doing before you start, and where you need to, you have to make sure that you can obtain the appropriate replacement parts.
Those preamps with digital logic circuits are a little more complex, but in general, proceed as follows:
1. Obtain the circuit diagram for your preamp (the Audio Research website has a great collection, only recently HUGELY improved.) Or buy a CD-Rom with the appropriate schematics from 'the bay'.
2. You DON'T want to be changing the large toroidal transformers. The schematic for your amp should show whether or not it has dual primaries. If so, you have a good chance. If not, I suggest you use an external US>European voltage converter.
3. On my preamp there WERE dual primaries, the blue and white are the centre tap wires that need to be connected and there is (on my preamp) a position on the circuit board to connect these.
4. If your preamp has a small PCB mounted transformer to supply the digital circuitry, it is unlikely to be dual voltage. In other words, you must obtain the correct voltage replacement. Audio Research did not help me with this. I initially bought a PCB transformer from a European transformer manufacturer, but the pins, although in the correct order, were a slightly different spacing. I am sure I could have paid a little more and had a custom made transformer built, but instead I approached an Audio Research distributor in my country and they obtained the correct transformer for me for a very reasonable price. I had an electronics engineer fit it for me.
5. Job done.
