OT Audio Adapter Query

[Rainer Straschill <moinsound@googlemail.com>]

Rick,

just so I'm getting this right:
You have:
  a) the rucksack with a stereo male 1/8 plug
  b) the Sonica with a (mono?) female 1/8 jack
  c) the cable which goes from stereo female to stereo male (extension 
cord)
  d) an mp3 player with female 1/8 jack for testing purposes.

Now I understand that somehow mp3 player through backpack does work,
and Sonica through backpack does not.
Which role does the cable (c) play here? Has it any effect on
working/non-working?
And another question: you mentioned that the Sonica will switch off
its speakers when something is plugged in. Does that happen when you
plug in your cable or the rucksack?

         Rainer