[WriteLog] codec performance, isolation transformers

[Eric Scace K3NA]

CODECS:

   There is a bewildering array of codec choices around.  As a HF/MF contester and DXer (CW, SSB and RTTY), I would like to be able
to listen to a contest or DXpedition recording and have a good chance of hearing that extremely weak station who was responding to
me while other nearby enormous signals were still calling.  This ability to handle a large dynamic range seems pretty demanding...

   Does anyone know of an authoritative site containing comparisons on the technical performance of various codecs?

ISOLATION TRANSFORMERS:

   The WL help files suggest using the small Radio Shack isolation transformers.  They work pretty well for RTTY signals at
2125/2295, but others have pointed out that performance in the lower frequency range is less than good with lots of distortion
products.

   A search of Mouser Electronic's catalog shows conventional audio isolation transformers are in the $50/each level.  That adds up
to serious money quickly.

   Confessing now to the fact that I am not an audio engineer, could someone more experienced in these matters suggest an approach
to choosing audio isolation transformers that introduce a minimum of impairments to receiver and transmitter audio?  My application
is pretty typical for a WriteLog-equipped contest station:
   -- computer with 2 soundcards.
   -- W5XD Multi+ keyer for SO2R operation.
   -- two transceivers, with ~1mW line-level audio input to the transmitter... and separate line-level audio output, speaker, and
headphone outputs.  For my particular transceiver of the moment, the headphone and speaker audio are from the same source.

   Thanks.

-- Eric K3NA