DC Blocker

The dc blocker is an indispensable tool in digital waveguide modeling [85] and other applications.^B.4 It is often needed to remove the dc component of the signal circulating in a delay-line loop. It is also often an important tool in multi-track recording, where dc components in the various tracks can add up and overflow the mix.

The dc blocker is a small recursive filter specified by the difference equation

where is a parameter that is typically somewhere between and (for a 44.1 kHz sampling rate, is good). The transfer function is

Thus, there is a zero at dc () and a pole near dc at . Far away from dc, the pole and zero approximately cancel each other. (Recall the graphical method for determining frequency response magnitude described in Chapter 8.)

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Subsections

• DC Blocker Frequency Response
• DC Blocker Software Implementations

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.