FREDs and Schottky diodes will mostly clean up the treble.
If you are looking for more transparency and dynamics, I suggest that you upgrade the amplifier coupling caps.
A few suggestions:
Low cost: Auricaps & Hovland
Medium cost: Mundorf Silver/oil
Expensive but the best IME: V caps TFT by VH Audio.
If you are looking for more transparency and dynamics, I suggest that you upgrade the amplifier coupling caps.
A few suggestions:
Low cost: Auricaps & Hovland
Medium cost: Mundorf Silver/oil
Expensive but the best IME: V caps TFT by VH Audio.