Real-time Digital Simulation of Guitar Amplifiers as Audio Effects

Práce se zabývá číslicovou simulací kytarových zesilovačů, jakož to nelineárních analogových hudebních efektů, v reálném čase. Hlavním cílem práce je návrh algoritmů, které by umožnily simulaci složitých systémů v reálném čase. Tyto algoritmy jsou prevážně založeny na automatizované DK-metodě a aproximaci nelineárních funkcí. Kvalita navržených algoritmů je stanovana pomocí poslechových testů.The work deals with the real-time digital simulation of guitar amplifiers considered as nonlinear analog audio effects. The main aim is to design algorithms which are able to simulate complex systems in real-time. These algorithms are mainly based on the automated DK-method and the approximation of nonlinear functions. Quality of the designed algorithms is evaluated using listening tests.

Design of Algorithms of Digital Audio Processing for Simulation of Guitar Combo Based on Circuit Analysis of Analogue Prototypes

Práce se zabývá simulací kytarového komba. Celá simulace je nejprve rozdělena na jednotlivé bloky. Dále jsou získány kmitočtové a převodní charakteristiky každého bloku obvodovou analýzou jejich analogových předloh. Vypočítané převodní charakteristiky jsou následně aproximovány a implementovány jako funkční měniče z důvodu snížení výpočetní náročnosti. Kmitočtové charakteristiky lze simulovat pomocí číslicových filtrů. Navržené algoritmy jsou nakonec implementovány jako plug-in moduly v jazyce C++.This work deals with computer simulation of a guitar combo. The complete simulation is divided into separate blocks and then transfer characteristics and frequency responses of each block are obtained from a circuit analysis of analogue prototype. After their aproximation, the transfer characteristics are implemented as waveshapers and frequency responses are simulated using digital filters designed according to their analogue prototypes. Designed algorithms are implemented as plug-in mudule in language C++.

Simulace kytarového předzesilovače v reálném čase pomocí aproximací a modifikované blokové netody

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.Návrh algoritmů pro simulaci analogových hudebních efektů přináší dva protichůdné požadavky - přesnost a nízkou výpočetní náročnost. Simulace kytarového předzesilovače v reálném čase pomocí aproximací a modifikované blokové netody je diskutována v tomto článku s ohledem na výpočetní náročnost. Řešení diferenciálních rovnic je předpočítáno a uloženo ve vyhledávacích tabulkách. Výsledky jsou porovnány s měřením na reálném předzessilovači

Quantitative morphology of cerebral thrombi related to intravital contraction and clinical features of ischemic stroke

Background and Purpose: The purpose was to assess quantitatively and qualitatively the composition and structure of cerebral thrombi and correlate them with the signs of intravital clot contraction (retraction), as well as with etiology, severity, duration, and outcomes of acute ischemic stroke. Methods: We quantified high-resolution scanning electron micrographs of 41 cerebral thrombi for their detailed cellular and noncellular composition and analyzed histological images for the overall structure with the emphasis on red blood cell compression, fibrin age, and the signs of inflammation. Results: Cerebral thrombi were quite compact and had extremely low porosity. The prevailing cell type was polyhedral compressed erythrocytes (polyhedrocytes) in the core, and fibrin-platelet aggregates were concentrated at the periphery; both findings are indicative of intravital contraction of the thrombi. The content of polyhedrocytes directly correlated with the stroke severity. The prevalence of fibrin bundles was typical for more severe cases, while the content of fibrin sponge prevailed in cases with a more favorable course. The overall platelet content in cerebral thrombi was surprisingly small, while the higher content of platelet aggregates was a marker of stroke severity. Fibrillar types of fibrin prevailed in atherothrombogenic thrombi. Older fibrin prevailed in thrombi from the patients who received thrombolytics, and younger fibrin dominated in cardioembolic thrombi. Alternating layers of erythrocytes and fibrin mixed with platelets were common for thrombi from the patients with more favorable outcomes. Thrombi with a higher number of leukocytes were associated with fatal cases. Conclusions: Most cerebral thrombi undergo intravital clot contraction (retraction) that may be of underestimated clinical importance. Despite the high variability of the composition and structure of cerebral thrombi, the content of certain types of blood cells and fibrin structures combined with the morphological signs of intravital contraction correlate with the clinical course and outcomes of acute ischemic stroke.Web of Science51123650364