I recently upgraded a Sansui Au505, which is a small low power amp that is capacitor coupled. Much credit for the results must go to Leestereo at Audiokarma.org, https://audiokarma.org/forums/index.php?threads/leestereos-restoration-upgrade-of-a-sansui-au-555a.816754/whose absolutely brilliant breakdown made this project a delight.
In common with other capacitor coupled amps, in this case Nichicon 4700uf 63v FW types, there is warmth to the overall sound, that is often described as tube like.
The power supply caps were all upgraded, using low impedance types, as were the power rail decoupling following the suggestions made by Leestereo. A number of Nichicon MUSE Bipolar caps were used in the audio path as where Panasonic and WIMA polypropylene film caps.Most of the ceramics were also replaced. A number of transistors were changed, as was the dual diode in the power supply. Everything was deoxed. The RIAA equalizer stage was rebuilt as per Leestereo’s suggestions. The Blaxandall bypass and Vbe multipler mods were also done and the trimmers. Overall the majority of the components were changed, which took longer than I thought, but the end result was very satisfying as the customer then stated in a text- “It sounds wonderful.So much more open and clean and crisp. The detail is really present. I ma very pleased and happy”- so now I am working on his Au 555.