12AT7 Tube
In order to model the 12AT7, we followed the exact same process as with the 12AX7. The resulting Input and Output are shown in Figure 1.
Figure 1. LTSpice Simulation Input and Output.
We then eliminated the time variable to find the input/output relationship to voltage as shown in Figure 2.
Figure 2. Input Output Relationship.
After fitting a cubic function to the line, we wrote the Matlab function pictured in Figure 3.
Figure 3. Matlab 12AT7 Function.
Below is an example of how the 12AT7 simulation sounds.
The effect of this tube is fairly similar to the 12AX7, so we feel similarly to that one about the quality of the results. It provides some distortion and amplification, but would be extremely difficult to perfect without true modeling using the exact circuitry.