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Posts

Plotting the FFT of a voltage signal

3 minute read

Published:

Plotting a signal in the frequency domain is a fundamental analysis tool which can provide great insight into the signal’s behaviour. Something I have struggled with in the past is getting the units correct such that the amplitude response of the frequency-domain representation has physical significance. In this blog post I aim to outline how to properly find useful units with which to represent voltage signals.

Measurement Gotchas: systematic error when averaging

2 minute read

Published:

When trying to capture a clean signal from an electronic circuit, a popular strategy is to use averaging. The circuit is driven by the same signal repeatedly creating a set of output signals which can then be averaged, thus reducing noise. I’ve used this technique a lot in the measurement step of my work on training physical models on measured data (see my DAFx-16 paper for more information).

Component meters: DE-5000 and M328

2 minute read

Published:

Recently I’ve been in need of measuring linear component values to a high degree of accuracy, so decided to purchase a couple of component meters. The first of these is the M328 “transistor tester”, which is a favourite of the DIY community as it is cheap and has all of the plans available on the internet. I put transistor tester in quotes as the meter is designed to measure resistance, capacitance, inductance, transistor type and basic characteristics, and even some parasitic properties. This is quite an impressive boast for a product which I purchased for £6.32!

Modelling logarithmic potentiometer laws

3 minute read

Published:

This post presents a general logarithmic potentiometer law with a curve fit to enable a user to choose a curve that sounds good in their application. The law is computationally expensive as it involves an exponent but is good in terms of flexibility.

Mathjax Test

less than 1 minute read

Published:

This is a test page to see if Mathjax is working. \(\pi\)

portfolio

publications

Improving the robustness of the iterative solver in state-space modelling of guitar distortion circuitry

Published in Proceedings of the 18th International Conference on Digital Audio Effects, Trondheim, Norway, 2015

Two methods are presented which attempt to reduce the expense of iterative solvers. This is achieved by applying information that is derived from the specific form of the nonlinearity.

Recommended citation: B. Holmes and M. van Walstijn. "Improving the robustness of the iterative solver in state-space modelling of guitar distortion circuitry", Proceedings of the 18th International Conference on Digital Audio Effects, Trondheim, Norway, Dec. 2015.

Download paper here

Physical model parameter optimisation for calibrated emulation of the Dallas Rangemaster Treble Booster guitar pedal

Published in Proceedings of the 19th International Conference on Digital Audio Effects, Brno, Czech Republic, 2016

In this work we explore optimising parameters of a physical circuit model relative to input/output measurements, using the Dallas Rangemaster Treble Booster as a case study.

Recommended citation: B. Holmes and M. van Walstijn. "Physical model parameter optimisation for calibrated emulation of the Dallas Rangemaster Treble Booster guitar pedal", Proceedings of the 19th International Conference on Digital Audio Effects, Brno, Czech Republic, Sept. 2016

Download paper here

Comparison of Germanium Bipolar Junction Transistor Models for Real-Time Circuit Simulation

Published in Proceedings of the 20th International Conference on Digital Audio Effects, Edinburgh, Scotland, 2017

The Ebers-Moll model has been widely used to represent Bipolar Junction Transistors (BJTs) in Virtual Analogue (VA) circuits. An investigation into the validity of this model is presented in which the Ebers-Moll model is compared to BJT models of higher complexity, introducing the Gummel-Poon model to the VA field.

Recommended citation: B. Holmes, M. Holters, M. van Walstijn. "Comparison of Germanium Bipolar Junction Transistor Models for Real-Time Circuit Simulation", Proceedings of the 20th International Conference on Digital Audio Effects, Edinburgh, Scotland, Sept. 2017

Download paper here

talks

teaching

Teaching experience 1

Undergraduate course, University 1, Department, 2014

This is a description of a teaching experience. You can use markdown like any other post.

Teaching experience 2

Workshop, University 1, Department, 2015

This is a description of a teaching experience. You can use markdown like any other post.