These replace stock inferior film caps in signal path and power supply positions in components such as amps, preamps, speaker crossovers, CD players, processors, etc.

Recommended: The absolute best found so far by a wide margin, but very expensive: Reliable Exotica Copper Foil Polypropylene Film, PCU capacitors.

Reliable: (562) 946-8577. Next best: Reliable aluminum foil/polypropylene Alpha capacitors.

Improved resistors should replace inferior metal film, carbon film and carbon composition resistors in at least the signal path and signal-to-ground (shunt) positions.

Recommended: Caddock TF020 metal-oxide film resistors (best), then Mills non-inductive wire-wound resistors.

Source: Michael Percy, 530-470-8650. Fast recovery diodes should replace stock standard power supply rectifier diodes. Source: Michael Percy (www.percyaudio.com) Other parts changes with less effect: electrolytic caps, wiring, sockets, etc. .