To convert balanced analogue audio to unbalnced or vice-versa:

• Use a couple of audio transformers mounted on a krone block.
  
  
  
  These can be inexpensive transformers (such as OEP model Z1604) or, as shown, top quality Sowter transformers.


• The transformers are stuck in place with double sided sticky foam (such as RS stock No.554 844)


• Compared to using an active balancing box it has the following advantages: it needs less space, it needs less cable and connectors, it uses no power so doesn't cost anything to run and it doesn't use up a mains socket, it's more reliable and less expensive.