How it works

The PT2253 implements an electronically controlled attenuator. The UP and DOWN buttons change its setting, and LM358 stages buffer the left and right channels. The original notes describe 32 attenuation settings over a nominal 0 to −68 dB range.

The stated supply range is 6–12 V. Allowable audio amplitude depends on the IC supply and biasing, so the archive’s 4 V RMS input claim should not be assumed valid at every supply setting.

Original schematic

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Figure 1 · NewCircuits archive · Download image ↓

On the bench

Check the PT2253 datasheet before choosing signal levels. Test both channels with a small input and confirm that each button changes the level cleanly without clipping.

Resources & provenance

Rewritten from the original circuits/aum/lj3on1t_aum015.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.

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