Tube modeling programmable digital guitar amplification system

A method of digitally amplifying an analog guitar audio signal in a portable housing unit comprising the steps of:

• converting an audio signal from an analog signal to a digital signal;
• digitally processing with a microcontroller said digital signal so as to emulate an analog guitar amplifier;
• converting said digital signal to an analog signal;
• amplifying said analog signal;
• and
• driving said analog signal through loudspeakers.

A digital guitar amplifier in a portable housing unit to digitally process audio signals comprising:

• an input jack for output from a musical instrument;
• at least one loudspeaker;
• a plurality of buttons and knobs for programming and storing program selections;
• a display for displaying selected programs;
• an analog to digital converter for converting an analog signal from said musical instrument to a digital signal;
• digital circuitry including a microcontroller for generating preamp effects, non-linearly amplifying said digital signal and generating linear effects;
• a digital to analog converter for converting said digital signal to a second analog signal;
• an amplifier for amplifying said second analog signal;
• and
• a driver to drive said second analog signal through said at least one loudspeaker.

A digital audio amplification system for digitally emulating a tube amplification system, comprising:

• means for digitally processing an input digital signal sampled at a first sampling rate by sampling and interpolating at least a portion of said input digital signal at a second sampling rate to produce an oversampled digital signal, said second sampling rate being a predetermined multiple of said first sampling rate;
• means for applying at least one nonlinear transfer function to said oversampled digital signal to produce a nonlinear oversampled digital signal;
• means for filtering said nonlinear oversampled digital signal to produce a filtered nonlinear oversampled digital signal with substantially reduced aliasing frequencies;
• and
• means for decimating said filtered nonlinear oversampled digital signal to output said filtered non-linear oversampled digital signal at said first sampling rate.

A digital audio amplification system for digitally emulating a tube amplification system, comprising:

• at least one input device for receiving an analog input signal from an external audio device;
• an analog-to-digital converter for converting said analog input signal to a digital signal at a first sampling rate;
• a microcontroller connected with an output of said analog-to-digital converter for receiving said digital signal;
• digital processing circuitry connected with said microcontroller for generating at least one of a preamplification effect, a nonlinear effect and a linear effect on said digital signal, said nonlinear effect including sampling said digital signal at a second sampling rate which is a predetermined multiple of said first sampling rate;
• a digital-to-analog converter for converting said digital signal to an analog output signal;
• and
• an output device for audibilizing said analog output signal.

A method for digitally emulating the tonal characteristics of a tube amplification system, comprising the steps of:

• digitally processing an input digital signal sampled at a first sampling rate by sampling and interpolating at least a portion of said input digital signal at a second sampling rate to produce an oversampled digital signal, said second sampling rate being a predetermined multiple of said first sampling rate;
• applying at least one nonlinear transfer function to said oversampled digital signal to produce a nonlinear oversampled digital signal;
• filtering said nonlinear oversampled digital signal to produce a filtered nonlinear oversampled digital signal with substantially reduced aliasing frequencies;
• and
• decimating said filtered non linear oversampled digital signal to output said filtered nonlinear oversampled digital signal at said first sampling rate,
• wherein said input digital signal is sampled at said second sampling rate chosen to emulate at least one of a specific predetermined set of tube amplifier characteristics.