Bass-boost audio amplifier

How it works

This mono amplifier combines audio gain with a frequency-dependent response that emphasizes bass relative to higher frequencies. The archive quotes approximately 1 W into a 4 Ω speaker; this is a historical estimate rather than a newly measured rating.

The circuit is useful for investigating how a feedback or coupling network changes frequency response. It is not a substitute for a high-power subwoofer amplifier, and a small speaker may not reproduce the lowest frequencies well.

On the bench

Use the speaker impedance shown in the schematic. Test initially at low volume and listen for clipping or excessive cone movement; compare the response at several input frequencies.

Resources & provenance

Rewritten from the original circuits/aum/lj3on1t_aum003.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.