1. Digital Modeling/Implementation of Valve Amplifiers
Cody Frye & Mitchell Gould

2. Agenda Introduction Motivation System Description Methods
Preliminary Results
Hardware Implementation Consideration
Bill of Materials
Schedule of Work

3. Introduction

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

5. Motivation Affordable, Cheap, and Convenient
Multiple Amplifiers to choose from
No Analog Components for reduced Component Size

6. System Description

7. System Description
The Preamp, Gain, Tone and Output blocks will be modeled according the schematic found online
Each block will be the WDF equivalent of the analog components making up the circuitry

8. Pre-Amplification Stage

9. Gain Stages

10. Tone Stack

11. Output Driver

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

13. Method 1 (Frequency Bin Method)
...

14. 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

15. Method 2 (Wave Digital Filters)
WDF Binary Tree for Triode Amplifier
WDF triode Stage (example) Binary Tree by Matti Karjalainen and Jyri Pakarinen

16. WDF Method Continued Wave quantities A = incident wave
B = reflected wave

17. WDF Method Continued
WDF 3 port adapters
WDF components

18. Preliminary Results Filter banks design High order bandpass filters
Difficult to implement in real-time
Not a sufficient method

19. Preliminary Results Simulated a RC High Pass Filter
Time Domain results using chirp signal (left)
Frequency Domain results (right)

21. High Pass Filter WDF Equivalent
Two Port Parallel Adapter
Analog RC High Pass Filter
Three Port Series Adapter

22. High Pass Filter (WDF)

23. Preliminary Results (Triode Valve)
Nonlinear Triode Currents as a Function of Vgk and Vpk
Triode Amplifier
Model of Triode

24. Preliminary Results (Triode Valve)
Leach’s Model Equations Norman Koren’s Model Equations

25. Preliminary Results (Leach’s model)
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

26. Preliminary Results (Koren’s model)
Vgk = 1
Vpk = 300
Vpk = 250
Vpk = 200
Vpk = 150
Vgk = 0
Vpk = 100
Vpk = 50
Vpk = 0
Vgk = -1
Vgk = -2
Vgk = -3

27. Hardware Implementation Consideration
Zynq 7000 FPGA/ARM Processor System on Chip (SoC)
Audio codec
Mikroe-506 Audio Codec Board
WM8731 IC
44.1kHz Sample Rate
Stereo
inter -IC sound (i2s) protocol

28. Bill of Materials Mikroe-506 Audio Codec Board - $19.38
Digilent PYNQ Board - $229.00
¼” female adaptors - (2) $0.86 per piece
Crate Blue Voodoo 120 Valve Amplifier - $ used

29. Schedule
Dates
Task
Assigned Too
1/19 - 2/2
Tone-stack WDF design/simulation
Cody
2/3 - 2/16
Triode valve WDF design/simulation
Mitchell
2/17 - 3/2
Pentode valve WDF design/simulation
3/3 - 3/16
Gain Stage WDF design
3/17 - 3/30
Overall Simulation
4/6 - 4/20
FPGA Hardware Configuration/Implementation
4/21 - 5/4
Student Expo and Final Presentation

30. Conclusion
Aims to digitally emulate Analog Circuitry of a valve amplifier using WDF
Implement on an zynq SOC device
Utilize i2s protocol