This listing is for a single NOS (New Old Stock) 12AX7 tube.

About the 6681 Industrial Tube

The 6681 is a "special 12AX7" designed for heavy-duty use in industrial and communication applications. While the electrical specifications match a standard 12AX7, this industrial-grade version features a ruggedized filament built to withstand frequent power cycles. Overall, the 6681 represents a significant step up in quality and durability from a standard 12AX7.

Our Guarantee & Warranty

• Performance Guarantee: We guarantee this tube will test as new with no gas or shorts (measured via Hickok Standard). If it does not meet these standards, we offer a full refund, including shipping costs.
• 1-Year Replacement Warranty: All vacuum tubes sold come with a 1-year warranty covering defects or failures.
• Hassle-Free Returns: If warranty service is required, simply return the tube; we cover the return shipping costs.

Rigorous Testing Procedure

To ensure you receive a tube that meets industry standards, we follow a strict testing protocol:

1.    Reference Testing: We utilize "bogie" or reference tubes for every model we sell.

2.    Comparative Analysis: The reference tube is tested first, followed immediately by the tube listed for sale to ensure accuracy.

3.    Calibrated Equipment: Our Hickok testers are calibrated monthly to provide precise and reliable results.

Shipping: $5.45 (Each additional tube: $1.00)