D&A stood for Delany and Adams AFAIK. Delany was a ham operator who went rogue and started building CB amps, or so I'm told. Adams, I believe was actually a woman- not sure if it was his wife or girlfriend or how she figured into the operation.
Delany was hounded by the FCC almost from the day he started building which is why no two D&A amps are exactly the same. It was a real cat and mouse game with Delany changing the design in an attempt to stay one step ahead of the FCC. In the end however, he just couldn't beat them and production ceased sometime in the early 1980s.
Curiously, Don Brewer of Brewer Labs (who made Varmint amps) escaped FCC scrutiny.
If you have access to the QST archives, I believe they have an article detailing how the FCC finally shut them down.