Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems 861v4 with ID40 & IA08

The backplanes are similar but not the same. The v4 in most configurations has to use terminator cards of resistors (internally) on the backplane to suppress unwanted reflections of signals across the backplane that can cause audible clicks or pops. The revised backplane presumably has a better geometric design (and may have some resistors integrated on the backplane - not sure about that) such that terminators seem no longer to be required. Also, the better design allows reliable operation at higher frequencies.

In principle, you could use later cards in a v4 but they would not be reliable (clicks and pops or worse because of higher frequency signals) so I assume M, quite rightly, inhibit that in firmware to avoid all the complaints that would ensue.

Changing a backplane, which is not an expensive item to make, is a very time consuming thing to do (I have done it on an 800 DVD machine when I was adding a blu-ray drive). So, although in theory you could upgrade a v4 to a v6 by changing the backplane, no dealer could do it economically - hence the trade-in programme as the way to get to v6 when the latter was first introduced.