While we do support custom domains for your Transistor-hosted podcast websites, we don't support using custom domains for RSS Feeds at this time. The main reason for this is for performance and reliability. RSS Feeds are constantly crawled by podcast directories and apps - sometimes thousands of times a day. Transistor serves your RSS Feeds from our global CDN to improve performance and decrease the likelihood of any downtime or interruption, and using the transistor.fm domain is required for this at the moment.
If you're worried about what happens to subscribers of you podcast should you leave Transistor for another hosting platform, we make it easy to redirect your Transistor RSS Feed to a new URL of your choice, eliminating any loss of subscribers. Your listeners won't notice any change at all.