Category Archives: Aliasing

Guitar amp simulation

In this article, I’ll sketch a basic guitar amp simulator. For one, questions on the topic come up often, and also, it will be a good example of a typical use of working at a higher sample rate. The most … Continue reading

Posted in Aliasing, Digital Audio, Sample Rate Conversion | 2 Comments

Wavetable oscillator video

If you find this video helpful, let me know, and I’ll work more video demonstrations into articles.

Posted in Aliasing, Synthesizers, Video, Wavetable Oscillators | 6 Comments

A wavetable oscillator—Part 2

From Part 1, we have an oscillator. But we need to broaden it to allow scaling of harmonic content based on pitch so that we have all the harmonic content we need at the low frequency end, and, as we … Continue reading

Posted in Aliasing, Digital Audio, Oscillators, Wavetable Oscillators | 12 Comments

Sample rate conversion: down

In doubling the sample rate, we inserted zeros between existing samples, then used a lowpass filter to remove the resulting alias in the audio band. To resample at half the current rate, we use a lowpass filter to remove audio … Continue reading

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A closer look at upsampling filters

Interpolation type:NoneZero-order holdLinearSinc 1Sinc 2Sinc 3  Show impulse response Sweep! In this demonstration, we generate a sine wave sweep from low in the audio band to near the Nyquist Frequency, which is half the sample rate. You can view it … Continue reading

Posted in Aliasing, Digital Audio, Filters, FIR Filters, Impulse Response, Sample Rate Conversion, Widgets | Leave a comment

Sample rate conversion: up

Once we have a suitable set of FIR filter coefficients from our windowed sinc calculator, it’s time to apply them. Again, our recipe for doubling the sample rate: 1) Insert a zero between existing samples. (This is the upsampling step, … Continue reading

Posted in Aliasing, Convolution, Digital Audio, Filters, FIR Filters, Sample Rate Conversion | 7 Comments

What is aliasing?

It’s easiest to describe aliasing in terms of a visual sampling system we all know and love—movies. If you’ve ever watched a western and seen the wheel of a rolling wagon appear to be going backwards, you’ve witnessed aliasing. The … Continue reading

Posted in Aliasing, Digital Audio | 14 Comments

Oversampling

In this discussion, “oversampling” means oversampling on output—at the digital to analog conversion stage. There is also a technique for oversampling at the input (analog to digital) stage, but it is not nearly as interesting, and in fact is unrelated … Continue reading

Posted in Aliasing, Digital Audio, Sample Rate Conversion | 4 Comments

Digital audio: theory and reality

The promise of perfect audio—the Nyquist Theorem Most people who’ve look at digital audio before know about the Nyquist theorem—if you sample an analog signal at a rate of at least twice its highest frequency component, you can convert it … Continue reading

Posted in Aliasing, Digital Audio, Dither, Jitter, Phase | 10 Comments