Yamaha DSP series amplifiers can be purchased second hand online at low cost. Older models have a common problem with the volume control because the volume control knob movement often does not correlate correctly with the dB level readout on the VFD screen reading.

The fault is due to the fact that the potentiometer damping grease used by Yamaha has dried up over time. The potentiometer can be refurbished and the dB level readout issue corrected with some effort and an application of a synthetic damping grease.

Read the full case study here or download the PDF version.