Because of it’s age the capacitors need to be replaced in this
heavyweight. Some capacitors where leaking and most didn’t match their values. Nichicon Fine Golds are the perfect audio capacitors as an upgrade.
After inspecting all the soldering joints came forward why the sound was distorted at higher volumes. Connected the amplifier on a dummy load and the Red Pitaya used as Spectrum analyzer at medium load there where some strange spikes visible, this is why:
Loose soldering joints on the power supply bridge, replacing with some new fresh solder did the job!
Time to RECAP!
And why not add a Furutech IEC inlet with EMI filter?
All the replaced capacitors and the relay