So, what prompted this change? Cambridge Audio has been busy working on a more upmarket player, the 740C but, in the process, it discovered a few tricks that it could put into the 640C.
The biggest of these changes is the introduction of two DACs, one per channel in dual-differential mode. This is a tried and tested route among more expensive brands and works much like balanced circuit topology to eliminate noise from the signal. Cambridge uses a pair of 24/192 Wolfson digital converters to improve stereo separation and the signal to noise ratio.
Another new feature is something Cambridge has dubbed a "four pole dual differential double virtual earth balanced topology". This means that each channel has two fully-balanced outputs that are summed, in order to "largely reject distortion", and then filtered again to reject noise introduced by the summing filter.
The 640C v2 has a new mains transformer and a revised LCD read-out with adjustable brightness, not forgetting a metal faced remote handset with navigator style controls.It also has control bus inputs and outputs as well as an IR emitter input for multi-room set ups. The rest of the connections are standard analogue and digital varieties.
There was a time, not so long ago, when even respected budget machines sounded pretty uncomfortable when played through high end systems. However, this is no longer the case. The latest 640C is highly listenable, even with a wide listening window. It can produce a very convincing sense of acoustic space thanks to its smooth, extended high frequencies and it underpins this with good bass weight and strong dynamic resolve.
It also has a tautness of presentation that reveals the articulation in playing styles and the placement of instruments in the soundstage. Imaging seems to live up to the hype too, with voices placed precisely above and between the speakers and singers delivering both the essence and the meaning of the song. Bigger orchestral pieces expand well into the room and deliver a good dollop of timbral character, but with this sort of material there's a slight lack of smoothness evident when the volume is pushed. But, who cares? A player this fluent at this price demands high praise.

Cambridge Audio Azur 640 v2| $850 | CD player |

For: Refinement and dynamic subtlety for the price. No better CD player this side of $1,000
Against: You could pay more to get a better sound and look.

Verdict: The latest 640C is more refined and musically engaging than its predecessor. It does most things extremely well and has a remarkably good sense of poise for the money – it's simply the cheapest way to get good CD sound at the moment