Simulation of a Vacuum-Tube Push-Pull Guitar Power Amplifier

Proc. of the 14 th Int. Conference on Digital Audio Effects (DAFx-11), Paris, France, September 19-23, 2011Proc. of the 14th International Conference on Digital Audio Effects (DAFx-11), Paris, France, September 19-23, 2011the amplifier properties was investigated. The loudspeaker wasmodeled using simplified electric circuit and Frohlich and Jiles-Atherton transformer models were used. The results showed thatthe output transformer had a minor impact on the simulation results.It only manifested at very low frequencies while the computationalcomplexity was increased significantly. Both transformermodels provided very similar simulation results and therefore, theFrohlich model is more efficient for real-time simulations.f [Hz]100001000100M [dB]40353025201510MeasuredJ−A modelFrohlichLoudspeakerConstant load100 0.5 1 1.5 2 2.5 3t [s]Figure 5: Spectrogram of output signal for simulation with JAmodel of transformer.50−5−1010 0 10 2 10 4f [Hz]Figure 3: Frequency dependence of the first harmonic content ofthe output signal.M [dB]3020100−10−20J−A modelFrohlichLoudspeakerConstant loadMeasured−300 100 200 300 400 500 600 700 800 900f [Hz]Figure 4: Output spectrum for input 90 Hz sinewave.6. ACKNOWLEDGMENTSThis paper was supported by the Fund of the Council of HigherEducation Institutions of the Czech Republic under project no.2704/2011 and project no. FR-TI1/495 of the Ministry of Industryand Trade of the Czech Republic.7. REFERENCES[1] J. Macak and J. Schimmel, “Real-time guitar tube amplifiersimulation using approximation of differential equations,” inProceedings of the 13th International Conference on DigitalAudio Effects DAFx10, Graz, Austria, Sep. 6-10, 2010.[2] D. Self et al, Audio Engineering, Elsevier, Burlington, MA,USA, 1 st edition, 2009.[3] U. Zölzer, DAFX - Digital Audio Effects, J. Wiley & Sons,Ltd, 1 st edition, 2002.[4] J. Pakarinen, M. Tikander, and M. Karjalainen, “Wave digitalmodeling the output chain of a vacuum-tube amplifier,”in Proc. Intl. Conf. on Acoustics, Speech, and Signal Proc.,Como, Italy, Sept. 1-4, 2009, pp. 55–59.[5] R. C. D. de Paiva, J. Pakarinen, V. Välimäki, and M. Tikander,“Real-time audio transformer emulation for virtual tubeamplifiers,” EURASIP Journal on Advances in Signal Processing,vol. 2011, pp. 15, 2011.[6] I. Cohen and T. Helie, “Real-time simulation of a guitarpower amplifier,” in Proceedings of the 13th InternationalConference on Digital Audio Effects DAFx10, Graz, Austria,Sep. 6-10, 2010.[7] N. Koren, “Improved vacuum tube models for SPICEsimulations,” Available at http://www.normankoren.com/Audio/Tubemodspice_article.html, 2003.[8] P. Kis, Jiles-Atherton Model Implementation to Edge FiniteElement Method, Ph.D. thesis, Budapest University of Technologyand Economics, 2010.[9] S. E. Zocholl, A. Guzman, and D. Hou, “Transformermodeling as applied to differential protection,” Tech. Rep.,Schweitzer Engineering Laboratories, Inc. Pullman, Washington,1999.[10] D. C. Jiles and D. L. Atherton, “Ferromagnetic hysteresis,”IEEE Transactions on Magnetics, , no. 5, pp. 2183–2185,1983.[11] D. C. Jiles, J. B. Thoelke, and M. K. Devine, “Numericaldetermination of hysteresis parameters for the modeling ofmagnetic properties using the theory of ferromagnetic hysteresis,”IEEE Transactions on Magnetics, vol. 28, no. 1, pp.27–35, 1992.[12] R. Elliot, “Measuring Thiele / Small Loudspeaker Parameters,”Available at http://sound.westhost.com/tsp.htm, 2007.[13] J. Pakarinen, M. Tikander, and M. Karjalainen, “Wave digitalmodeling of the output chain of a vacuum-tube amplifier,” inProc. of the Int. Conf. on Digital Audio Effects (DAFx-09),Como, Italy, Sept. 1–4, 2009.DAFX-4DAFx-62