OUTPUT CAPACITOR: There is widespread mistrust of electrolytic capacitors, especially when used for speaker coupling. I have seen them accused of reverberation, hysteresis and several other forms of unmusical behaviour. The real effects include a little low-order harmonic distortion, and a capacitance and equivalent series resistance which depend on the frequency, effects which can easily be misinterpreted. My previous design demonstrated that low distortion was possible when including the capacitor in the overall feedback loop, and this is again done here, but with far higher loop gain. The advantages are considerable, including the need for only a single supply voltage, and avoidance of switching contacts in series with the speaker, which are otherwise needed to provide speaker protection in case of large output offset voltages resulting from fault conditions. The capacitor prevents any dc output other than a small leakage current reaching the speaker. Speaker protection is missing from many published designs, but is really essential. Reliability problems with relay contacts persuaded me to reconsider output capacitors, although it looked at first like a backward step. I have never experienced capacitor failure in audio circuits although I spent many years repairing electronic equipment and have an amplifier of my own design which has been in regular use for over 30 years. The 'lifetime' specifications for electrolytics are generally at the maximum temperature rating, and lifetime is often claimed to double for every 10deg.C reduction. Use of the 105deg.C rated types should increase lifetime typically 4 times compared to the 85deg.C types with the same lifetime rating. Electrolytics are of course not close tolerance components, and some variation and long term drift in characteristics must be expected and taken into account. Other output capacitor 'problems' include reduced bass damping factor and possible large switch-on thump as the capacitor charges through the speaker, which are both reduced by the overall feedback. The output capacitor used was actually two 2200uF in parallel. The larger total surface area compared to a single 4700uF will help keep the temperature down and further improve lifetime