# Category Archives: Sample Rate Conversion

## Amp simulation oversampling

In tandem with our last article on Guitar amp simulation, this article gives a step by step view of the sampling and rate conversion processes, with a look at the frequency spectrum. From guitar to digital The first two charts embody the … Continue reading

## 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 | 3 Comments

## A wavetable oscillator—Part 1

There are many ways to make an oscillator. Without looking for further motivation, I’ll propose a wavetable oscillator. Wavetables are a fairly obvious extension of the general playback of digital audio. Such oscillators are easy to understand, and their extreme … Continue reading

## 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

## 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

## 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

## Building a windowed sinc filter

As promised, here’s our windowed sinc calculator for building a 2x oversampling filter:  Factor  Length  Rejection  Gain Notes: Use the Tab or Enter keys to effect changes (most browsers), or press Calculate. The frequency axis is in multiples of the … Continue reading

## Towards practical resampling

In a previous article, we looked at sample rate conversion in the frequency domain. Let’s take a quick second look in the time domain as reinforcement of principles behind sample rate conversion, before developing a practical rate convertor. In an … Continue reading

## Sample rate conversion

Here we explain how sample rate conversion works. As an essential prerequisite, you must understand the principals of sampling. Even if you understand sampling already, read our explanation of the process here. The viewpoint and terms used there are mirrored … Continue reading

Posted in Digital Audio, Sample Rate Conversion | 16 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