G'Day Felix!!
Good topic! Some random thoughts...
Some electrolytics sound far better than others. Low leakage caps tend to sound better than standard.
Electro caps have been used in high end signal path since the beginning. When large value is needed, often there is no better solution. My Sansui tuner's FM section has lots of old orange electros insignal path, but sounds wonderful.
Some very popular small film caps are more colored than the best electros.
The large value cap in your phono stage is for RIAA curve EQ. It would be difficult to find a decent film cap that big, let alone afford one of that value with ultra fidelity pedigree or whatever you wanna call it. So the designer made a wise choice using a good sounding electro over big expensive potentially worse sounding film.
[snip] whilst I wouldn't use an electrolytic capacitor in a signal path, surely there are places where the use of an electrolytic capacitor is quite ok like this. [snip]
Opamps have 100dB open loop gain, so a lot of negative feedback is needed in audio circuits. The negative feedback is added directly and perfectly to the positive so whatever distortion is in the feedback loop will be in the signal output, tho inverted. How much affect is determined by the amount of feedback. So feedback components really are in the signal path, practically speaking.
