I've been having a look at this AU-α907Limited, and the overheating it seems to have suffered. I discovered the probable reason, i.e. that the bias was set at something around 40mV (should be 28.6mV) for both channels, the somewhat higher setting (45mV) was for the Driver/OP module pictured below. Here are some pictures of one Driver/Output assembly Here is a close up - showing the shrunken sleeves of the 4 capacitors (2 pairs of 2) in the foreground centre. I have removed the worst looking two (they are 2.2µF 50V) and measured them, they have different ESR's at 0.49Ω & 2.0Ω although the values seem to have held well. The combination, they are joined + to + to form a bipolar, measures 5.0Ω ESR. I think they have obviously suffered some heat stress, and really should be replaced - however 'Elna Silmic α Super Gold' capacitors don't seem to be around any more from a reliable source. So, I am thinking of replacing them with some nice films - one film capacitor per original pair, which will fit very well in the space available. Elna Silmic II, or Nichicon Muse ES would seem to be the only other choices. My thinking here is, 'why not take the opportunity to get rid of 2 electrolytics' in favour of films. Any thoughts?