audio.conf missing

The audio.conf file is not needed. There is a bug in either Bluez or Pulseaudio causing issues if you want to use A2DP

A current work around is to

wget https://gist.github.com/pylover/d68be364adac5f946887b85e6ed6e7ae/archive/d698974910bbb7d016ec0ad08c1bf41b4b524364.zip
mv ~/d68be364adac5f946887b85e6ed6e7ae-d698974910bbb7d016ec0ad08c1bf41b4b524364/a2dp.py .a2dp.py

Then after connecting to the headset run ./a2dp.py in terminal and enter the number for your headset and let the python script do the rest

Simply apply your required changes on /etc/bluetooth/main.conf instead of /etc/bluetooth/audio.conf as this file has been removed in new versions.

and for solve Failed to connect to SDP server on FF:FF:FF:00:00:00 see below link and make some changes on dbus-org.bluez.service to use features of blueZ-4 as sdptool in blueZ-5 not work properly.

https://raspberrypi.stackexchange.com/questions/41776/failed-to-connect-to-sdp-server-on-ffffff000000-no-such-file-or-directory

Get the index of your card:

pacmd list-cards

Set the cards profile to a2dp (example: index 2):

pacmd set-card-profile 2 a2dp_sink

Credit to develmusa of the ArchLinux forums: https://bbs.archlinux.org/viewtopic.php?pid=1720877#p1720877