If you want to polish up your transcription, check this out:
A native speaker of American English reading out sequences of words with a focus on one particular sound of GA. Very useful if you still have difficulties in "hearing" the difference between some sounds of GA:
http://audio-class.ru/english-phonetics.html
http://usefulenglish.ru/phonetics/listening-for-vowels
(Remember to ignore the vowel length.)
A bunch of exercises on various aspects of transcription. I highly recommend the exercises on -ed and -es endings:
http://www.telefonica.net/web2/eseducativa/phonetics/indexa.html
http://www.telefonica.net/web2/eseducativa/phonetics/indexb.html
