DC offset accumulates in feedback delay loops and must be filtered with a sub-audio highpass

DC offset is a constant positive or negative component in an audio signal (frequency = 0 Hz). In a delay loop with feedback it recirculates every repetition. At high feedback settings the DC accumulates, potentially taking the signal outside the audio interface’s amplitude range and causing distortion. The fix is simple: insert a highpass filter with very low cutoff (e.g. 10 Hz) inside the feedback path. This removes the DC component (0 Hz) without affecting any audible frequencies. The same filter also removes accumulated low-frequency rumble from each repetition.

Examples

Delay with 0.95 feedback on a signal with DC offset: DC recirculates with every echo, eventually clipping the output. Fix in Max: vs.butterhp~ with 10 Hz cutoff inside the tapin~/tapout~ feedback path. Side benefit: eliminates low-frequency buildup in tape-delay simulations.

Assessment

Explain why a 10 Hz highpass filter inside a delay feedback loop prevents DC accumulation. Draw the signal flow showing exactly where the highpass filter is inserted.