Adrian

I have read about inefficient codec’s being adopted forcing a reduction in bit rates to accommodate the high number channels etc. but I don’t know how serious the threat of a change of system is.  I’d be surprised if the change rendered existing tuners obsolete as that would probably cause uproar so soon after introduction.  

Bit rate isn’t the only thing that affects sound quality but it’s worth noting that Sky and Freeview radio channels are usually broadcast at a higher bit rate than DAB equivalents.  So if you have Sky or Freeview you may want to consider using that as your radio source.  I ended up doing this via Toslink from my Sky box into a DAC that has a crack at up-converting the digital sample.  This puts a bit of space and sparkle into the music compared to using the audio output direct from the Sky box.  It’s fair to assume therefore that a good dab tuner with a decent built in DAC and good downstream electronics will sound better than the (presumably) basic audio circuit on the Sky box RCA output, even if the bit rate is lower.  But if you already have Sky or Freeview it’s worth a try. 

As with any fixed rate, low bit compression format I have heard, the more complex the music is the flatter and coarser the sound becomes.  This holds true for Sky radio and I assume DAB.  Not all channels that use the same bit rate sound the same either, some sound noticeably better than others.  Accepted wisdom says that this is down to different encoding but clumsy use of transmission maximisers/dynamics processors is probably as much to blame for the ones that sound flat.  Again I am talking about Sky but I understand the same to be true for DAB.  Not a straight answer to your question but I hope this background info is of interest.