Do you use Megaphone to host your regular show, but want to easily be able to sell ad-free feeds to your users without uploading two feeds at a time? 

You can do that. Read more below, and thank you to Megaphone's website for the information (see the full source here). 

The "Multiple Feeds" option is found on the "Megaphone Settings" tab.

Once you've enabled Multiple Feeds, click on the "Feeds" button to manage your feeds for this podcast.

Generating Duplicate Feeds

You can use this interface to generate duplicate RSS feeds for the podcast. All feeds generated in the "Feeds" tab will include all advertisements targeted specifically at the new feed, and all feeds generated in the "Ad-Free Feeds" tab will exclude advertisements.