DISCLAIMER: This post describes how to access the phone's hidden programming menu. USE AT YOUR OWN RISK. The changes I describe have been used by many people with the Droid 1 and other Android phones.
I strongly recommend that you stay out of the other areas of this menu unless you know exactly what you are doing.
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This has been discussed many times over at DF, but I thought I'd share for those of you that weren't a Droid 1 convert and may not have seen this.
Pull up the dialer on your phone
Dial ##PROGRAM (##7764726)
Hit Send (the call button)
The password is 000000 (six zeros)
Select option 04 (Vocoder)
There are three options: 13K, EVRC (default), and EVRC-B
Choose EVRC-B and hit apply
Back out of the menu to your home screen
The phone will reboot on its own
This option uses a higher quality voice compression codec. The result should be an improvement of audio quality in calls. Some technical information about EVRC and EVRC-B can be found HERE.
TEST THIS AFTER IMPLEMENTATION.
EVRC-B, while available in most areas, is not available everywhere. If you find you are unable to place calls, go back into the menu and choose EVRC.