Optimal Extraction and Statistical Analysis of Physical Model Parameters for Nonlinear Properties of Triode Vacuum Tubes

Abstract

The purpose of this paper is to estimate the manufacturing-related variation factor from the difference in variance and correlation of the high-precision physical model parameters for a miniature triode vacuum tube 5751 with an amplification factor of 70. The vacuum tube operating model used here is based on physical equations adapted to the large signal input behavior of vacuum tubes used in guitar amplifiers and incorporates the effect of modulation of the amplification factor. This improves the accuracy of the soft clipping and hard clipping characteristics that affect the spectrum of the distortion sound. In order to improve the accuracy of the extraction of such multivariate model parameters, we devised a new analytical formula. In addition, we devised an algorithm for sequential regression analysis of the simulated and measured values against the analytical equation, and all parameter extraction was performed automatically by a computer program. As a result, correlations between the parameters, which had not been found before, were confirmed, and it became clear that the manufacturing and assembly accuracy of the grid electrode strongly affected most of the physical parameters.