Digital Modeling/Implementation of Valve Amplifiers Authors: Cody Frye & Mitchell Gould Advisor: Dr. Yufeng Lu Department of Electrical and Computer Engineering May 4th 2019

Agenda Introduction Motivation System Description Methods Triode Valve Numerical Analysis WDF Results Conclusion

Introduction Significance of valve amplifiers Pros of valve amplifiers Smooth clipping Warm tone characteristics Cons of valve amplifiers Weight Heat Cost

Introduction

Motivation Affordable and Convenient Variety of Amplifiers to choose from Digital components reduce overall size

System Description

Pre-Amplification Stage

Methods Frequency Bin / Lookup Table Method Model Individual Blocks of System Wave Digital Filtering

Method 1 (Frequency Bin Method) ...

Method 1 (Frequency Bin Method) Separate input signal into Multiple frequency bins bandPass Filters NonLinear transfer function represented by L.U.T.s Sum all the bins together

WDF Method (Method 2) Wave quantities A = incident wave B = reflected wave A = V + RI [eq. 1] B = V - RI [eq. 2] V = (A+B) / 2 [eq. 3] I = (A-B)/2R [eq. 4]

WDF Method (Method 2) WDF components WDF port adapters

Triode Valve Numerical Analysis Nonlinear Triode Currents as a Function of Vgk and Vpk Triode Amplifier Model of Triode

Triode Valve Numerical Analysis Norman Koren’s Equations Leach’s Equations

Leach’s model Vgk = 2 Vgk = 1 Vgk = 0 Vgk = -1 Vgk = -2 Vgk = -3 Vpk = 350 Vgk = 2 Vpk = 300 Vpk = 250 Vgk = 1 Vpk = 200 Vpk = 150 Vgk = 0 Vgk = -1 Vpk = 100 Vpk = 50 Vpk = 0 Vgk = -2 Vgk = -3

Koren’s model Vgk = 1 Vgk = 0 Vgk = -1 Vgk = -2 Vgk = -3 Vpk = 300

Triode Valve Numerical Analysis

WDF 1st Order LPF RC LPF Circuit WDF Equivalent

WDF 1st Order Filter PSpice simulation results for 1st Order LPF WDF simulation results for 1st Order LPF

WDF Single Triode Stage Amplifier Single Stage Circuit Single Stage WDF equivalent

WDF Single Triode Stage Amplifier Single Stage Circuit Single Stage WDF equivalent

WDF Single Triode Stage Amplifier Single Stage Circuit Single Stage WDF equivalent

WDF Single Triode Stage Amplifier Single Stage Circuit Single Stage WDF equivalent

WDF Single Triode Stage Amplifier Single Stage Circuit Single Stage WDF equivalent

WDF Single Triode Stage Amplifier PSpice Triode Stage WDF Triode Stage

WDF Single Triode Stage Amplifier WDF G Chord results

Conclusion In this project, a digital emulation of an analog valve amplifier has been designed. The non-linear characteristics of valve amplifier has been modeled. The overall response of the valve amplifier has been successfully emulated using Wave Digital Filtering technique.

Future Work Model distortion characteristics of real amplifier using cascaded amplification stages and self-tuning algorithm Implement WDF system including R-Adapter on an ARM-based embedded system

Questions? Thank you!

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