Before audio legend Bob Carver founded Carver Corporation, he founded Phase Linear, in 1970.
Phase Linear debuted with two enormously powerful amplifiers, the 700 and 400, along with the Model 4000 preamplifier. Shortly thereafter, however, Carver left the company to form Carver.
Phase Linear continued to produce some well-regarded products, including a line of source components, and eventually was sold to Pioneer. Today, the company is owned by Audiovox and like most brands assimilated into that collective, it it has essentially no ties to the company it once was. If you can find the Phase Linear name today, it is on car audio equipment or co-branded with Jensen. As an example of how far the brand has fallen, it doesn't even have its own web page.
For an in-depth history, check out the Wikipedia article.
If you're feeling really nostalgic you can check out PhaseLinearHistory for a look back at all the products.