I would like to thank Steve because the above problem ended with the new cable I received today from 'Sounds Heavenly'!

Thank you, the above problem occurs with the sony walkman NWZ-S639F. There is a setting for AVLS (automatic volume limiting system) but it makes little difference by switching it off: to get a decent sound the mp3 volume needs to be set at maximum (30) and the beocenter 2500 at more than 70 and then it starts to sound 'noisy'. Google search

any more intelligent technical advice please?...

Any idea why such a relatively low output from beocenter 2500 when connected to a reasonbly good mp3 player?