Báo cáo hóa học: Research Article Real-Time Guitar Preamp Simulation Using Modified Blockwise Method and Approximations Jaromir Macak and Jiri Schimmel

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Báo cáo hóa học: " Research Article Real-Time Guitar Preamp Simulation Using Modified Blockwise Method and Approximations Jaromir Macak and Jiri Schimmel"Hindawi Publishing CorporationEURASIP Journal on Advances in Signal ProcessingVolume 2011, Article ID 629309, 11 pagesdoi:10.1155/2011/629309Research ArticleReal-Time Guitar Preamp SimulationUsing Modified Blockwise Method and Approximations Jaromir Macak and Jiri Schimmel Faculty of Electrical Engineering and Communication, Brno University of Technology, 61600 Brno, Czech Republic Correspondence should be addressed to Jaromir Macak, jaromir.macak@phd.feec.vutbr.cz Received 14 September 2010; Revised 12 December 2010; Accepted 27 January 2011 Academic Editor: Vesa Valimaki Copyright © 2011 J. Macak and J. Schimmel. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The designing of algorithms for real-time digital simulation of analog effects and amplifiers brings two contradictory requirements: accuracy versus computational efficiency. In this paper, the simulation of a typical guitar tube preamp using an approximation of the solution of differential equations is discussed with regard to accuracy and computational complexity. The solution of circuit equations is precomputed and stored in N-D tables. The stored values are approximated, and therefore different approximation techniques are investigated as well. The approximated functions are used for output signal computation and also for circuit state update. The designed algorithm is compared to the numerical solution of the given preamp and also to the real preamp.1. Introduction with a grid current is presented in [7]. A decomposition into a linear dynamic and a nonlinear static part is used inThe real-time digital simulation of analog guitar effects and nonlinear state-space formulations [8, 9] and this methodamplifiers has always been, unfortunately, a compromise was automated in [10], where the algorithm parametersbetween accuracy and speed of a simulation algorithm. are derived from the SPICE netlist. An extended state-There are many different approaches to the simulation, space representation was used in [11] for guitar powerampsuch as a black box approach, a white box (informed) simulation. A direct solution of nonlinear circuit ordinary differential equations (ODEs) was used in [2, 12], butapproach, circuit-based approaches, and so forth [1]. Allthese algorithms differ in accuracy of the simulation as well as the computational requirements are high. Therefore, an approximation of the solution of ODEs was used in [13].in computational complexity. The circuit-based techniquesusually offer the best accuracy because a simulated circuit However, an approximation of nonlinear functions are alsois exactly described by circuit equations, which are often used in [6, 10].differential equations. Nevertheless, the computational com- In this paper, a typical guitar preamp is simulated using the approximation of a solution of differential equations.plexity needed for a solution of these equations is very high[2]. Hence, more efficient algorithms for the solution of First of all, the guitar preamp is decomposed into separatethe equations must be found. This can often be made by blocks. It is necessary to find a proper division, because it can influence the accuracy of the whole simulation. A commonlyneglecting unimportant factors, for example, tube heating,decomposing into separate blocks [3], and decomposing used division into blocks does not consider mutual interac-into a linear and nonlinear part. Subsequently, the separate tions between connected blocks. As was shown in [13, 14], the simulation fails especially if the load of the simulatedsimplified block can be described by a new set of circuit block is nonlinear, which is typical for circuits with tubes.equations that can be solved using several methods, fore ...