The GAP/R K2-W Vacuum-Tube Op Amp in SPICE (Part 4): LTspice Files

As a service to our readers, we're providing the LTspice files used in Dr. Dyer's article on simulation of the 12AX7 and the K2-W vacuum-tube op amp.
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Dec. 9, 2024
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As a service to our readers, we're sharing Stephen Dyer's LTspice files from his Electronic Design article "Modeling on Mondays: The GAP/R K2-W Vacuum-Tube Op Amp in SPICE (Part 4)."

Stephen A. “Jack” Dyer
1. The model for the K2-W is established as a hierarchical block in LTspice, with the schematic as shown. The two 62-V independent voltage sources represent the two neon lamps used in the actual circuit as voltage regulators. Positive feedback is applied to the second stage via resistor R7. Capacitor C1 is a Miller-effect capacitor.
1. The model for the K2-W is established as a hierarchical block in LTspice, with the schematic as shown. The two 62-V independent voltage sources represent the two neon lamps used in the actual circuit as voltage regulators. Positive feedback is applied to the second stage via resistor R7. Capacitor C1 is a Miller-effect capacitor.
Stephen A. “Jack” Dyer
2. The LTspice schematic of the K2-W op amp in a basic inverting configuration incorporates the symbol created for the K2-W model. The gain G is set to ‒1. Two power supplies, +300 V and ‒300 V, are required for operation. The voltage source Vos_null compensates approximately for the K2-W’s inherent input-offset voltage; the details of the bias-adjustment circuitry aren’t shown.
2. The LTspice schematic of the K2-W op amp in a basic inverting configuration incorporates the symbol created for the K2-W model. The gain G is set to ‒1. Two power supplies, +300 V and ‒300 V, are required for operation. The voltage source Vos_null compensates approximately for the K2-W’s inherent input-offset voltage; the details of the bias-adjustment circuitry aren’t shown.

K2-W and 12AX7 LTspice files c.2024 Endeavor Business Media

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