Stand-alone instrumentation is described which, when fed with an input signal derived from a simple electric violin, replicates the timbre, voice and and tonal characteristics of an acoustic violin. The system, which operates in real time, is programmed with the impulse responses of a number of high quality, and in some cases almost priceless, acoustic instruments. These include models built by Catenari, Guarneri, Stradivarius and Tononi. The incoming signal is first amplified, digitized and then convolved with the chosen impulse response; this latter operation employs a fast digital signal processing (DSP) core executing a zero-overhead time-domain algorithm. The result is then converted back to analogue form and transmitted to a buffered audio driver. Controlled listening studies and professional violinist assessment have confirmed that the modified output signal is both authentic and convincing. The acoustic calibre is determined in large measure by the manner in which the impulse is obtained, the speed of the convolution algorithm, the resolution of the converters and the use of high quality components that guarantee a low audio noise floor. The device, which is intended for live performance, is realized as an effects pedal incorporating standard 1/4 inch phono sockets for input and output, two footswitches for single-touch instrument selection, a simple display, USB interface and an industry standard power system. The instrumentation and software also comprise a number of other features, including automated loudness correction, pickup preamplification and output equalization. In its typical manifestation, the unit holds in its memory the impulse responses of violins whose combined value is in excess of ￡12M.
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