Dolby output when PCM selected

[pastim]

I have a 7700 HSCI (23022) running 7.01.10 (the last official firmware I have found).

I use the SPDIF output set to PCM for audio, since I do not have a surround-sound system, but prefer to use the high quality DAC in my pre-amplifier than the one in the Topfield.

Until recently I have had no problems, and could listen to all channels I have tried, both UK and other European channels.

In the UK the BBC have started transmitting some HD channels with only 1 audio track - a Dolby one. Looking at Lyngsat and other satellite information websites it seems that almost all other HD channels have both a Dolby and a plain stereo audio channel.

On these new HD channels with no plain audio track the Topfield appears to output in Dolby on the SPDIF, even though I have selected PCM in the setup. The sound is completely garbled and incomprehensible.

I stress that I only have this problem on channels which do not have a plain audio track, and that this seems an unusual and new development.

I have tried using the analogue output with these new HD channels, and this works OK. I think this means that the decoding from Dolby to stereo in the 7700 does work, but is not being used for SPDIF even when PCM is selected as the output format.

Is this a known problem? Is there a firmware fix available?

With apologies for not trying to write in German....