Inserting a Shortcode into conditional with Custom Field

OK, so i have a custom field that is specifying the URL of an MP3 file for a podcast, and the end goal is for that URL to be inserted into the shortcode for the audioplayer…

which looks like this [audio:https://domain.com/audio.mp3%5D

SO I need something in the theme that says …

if there us something in the mp3_link field
[audio: *stick it right here*]

<?php $values = get_field('mp3_link');
	   if($values)
   {
    echo '' . do_shortcode(' [audio:$values] ') . '';
   }
    ?>

I know i am missing something… this is the code i have and it returns [audio:https://domain.com/audio.mp3%5D but …not as code, but as text —?so it’s not being translated to the audio player.

Eh?