Kay Musical Instruments of Chicago was the first company in 1962 to manufacture guitar amps that were 100% solid-state electronics. Here are some vintage advertisements from that time period.
The first ad, Transistorized Amplifiers, I found as a JPEG somewhere on the Internet years ago. Unfortunately I can’t remember where I found it, and can no longer find the source to give proper credit. If anyone knows, please give a shout. The second ad, Kay Vanguard, features the 1966 Kay Vanguard Electric Guitar and 704 Vanguard Amp, and was purchased from a seller on eBay.
Transistorized Amplifiers — An Exclusive
• Space Age Technology and Design
Published 1965. Triumph of top designers, engineers–and Kay! . . . Makes all others obsolete!
Kay Vanguard Electric Guitar and Amplifier
• Professional Sound & Style… On a Budget
Published 1966. Kay presents the most professional sound in an electric guitar and amplifier ever offered for under $200…
You can sound like the “pros” and look the part with this beautiful new Kay Vanguard Vibrato Electric Guitar and Vibrato Amplifier… And you get the exclusive “Thin-Lite” neck with adjustable truss rod for lightning fast action, vibrato tailpiece (for modern sound effects), 6 keys on one side, separate tone and volume control, adjustable rosewood bridge, inlaid position markers, shaded cherry red finish… Kay Musical Instruments— Division of Seeburg Musical Instruments, 2201 W. Arthur. Elk Grove Village, Ill. 60007.