The SEA-1 was the first single-ended amp built to use the One Electron UBT-1 output transformers. Not really presented as a construction project, the SEA-1 is a good source of ideas for single-ended amp design. It was the predecessor of the Randall Amplifier.
An application note describing the SEA-1 was published by One Electron in 1994. This note was published essentially unchanged in the Fall 1994 (issue #7) issue of Sound Practices magazine on page 26.
Here is the SEA-1 application note in Adobe Acrobat format:
SEA-1 App. Note (PDF: 93Kbytes)
(Note: Acrobat has altered the fonts from their original, but this doesn't affect readability or accuracy.)