Koss E/9 Electrostatic stereophone Headphone energizer as is for parts(untested)

Koss E/9 Electrostatic stereophone energizer as is for parts(untested) in Very Good condition

• Some wear for its age
• Untested as is for parts
• Comes with 5-prong cord see photo 2

Unlock the full potential of your vintage Koss electrostatic headphones with the Koss E/9 Energizer. This robust power source was the heart of the legendary ESP/9 studio monitor system, designed to provide the high-voltage bias and signal transformation required for true electrostatic transparency.

Whether you're restoring a classic ESP/9 setup or need a reliable energizing source for your 5-prong Koss electrostats, this unit delivers the wide frequency response and low distortion that set the standard for critical listening in the 1970s.

Why?:

• Dual-Power Flexibility: Can be operated as a self-energizing unit (drawing bias from the audio signal) or via the AC line for more precise, high-level monitoring.
• Speaker Pass-Through: Features rear speaker terminals and a front-panel Speaker/Phone switch, allowing you to keep your main monitors connected while switching to headphones for private listening.
• Massive Transformers: Equipped with heavy-duty coupling transformers designed for a 10-octave response range, providing clean power down to 20Hz.
• Classic Build: A rugged, black-anodized front panel with the iconic vintage Koss aesthetic.

In the Milwaukee Area? Stop in our shop to inspect/demo

See our feedback and thank you for considering. All the gear we sell is packaged with great care for safe arrival in the condition advertised and backed up by our 14 day full refund policy in the event you are not happy for any reason.

Local Pickup at our shop in Milwaukee, WI

Milwaukee Vintage
10220 W. Greenfield Ave
Milwaukee, WI
Open Tues-Friday 11-6
Saturday 11-3