Gibson Maestro Plus 50 50W Solid State Power Amp

The Maestro by Gibson Plus 50 is a rare solid-state auxiliary amplifier produced in Kalamazoo, Michigan during the mid-1960s. Designed as part of Gibson's "Sound Expansion System," the Plus 50 served as a powered extension cabinet, adding an additional 50 watts of clean output to any compatible amplifier. Housed in a compact black-tolex enclosure with dual 10-inch speakers, it delivered transparent amplification without tonal coloration—ideal for guitar, accordion, or organ setups of the era.

This example is in very good vintage condition, showing moderate cosmetic wear consistent with age. The cabinet covering shows scuffs and marks throughout, but remains structurally solid with intact grille cloth and original hardware. All functions operate properly. The back panel features a single Volume control with ¼" Input and Output jacks. Internally, it retains its original solid-state power section and CTS speaker complement.

Specifications

• Make: Maestro by Gibson
• Model: Plus 50 Auxiliary Amplifier
• Serial Number: 539
• Year: 1966 - 1967
• Country of Manufacture: USA (Kalamazoo, MI)
• Power Output: 50 Watts RMS
• Amplifier Type: Solid-State (6 Transistors / 8 Diodes)
• Speakers: 2 × 10″ CTS AlNiCo Drivers (8 Ω Load)
• Controls: Single Volume Control on Rear Panel
• Inputs / Outputs: ¼″ Input (Line / Amp Ext Speaker), ¼″ Output (Extension Out)
• Cabinet: Closed-Back Combo Enclosure
• Covering: Black Vinyl / Tolex with Silver Grille Cloth
• Power: 120 V AC Two-Prong Cord (Original Spec)

Condition

Used, very good vintage condition with visible scuffing, edge wear, and light discoloration to the tolex and hardware. Original speakers remain intact and functional. The circuit operates correctly, producing clean solid-state output with no hum or crackle. Fully tested and ready for use or display.

2-Prong extension power cord not included