SDG #025 Cambridge Audio A4 Amplifier Modifications

The Cambridge Audio A4 is a budget integrated amplifier from an era when decent audio hardware still used through hole construction and generously sized linear power supplies, which makes it an ideal candidate for refurbishment rather than replacement. This project strips the unit down to the bare chassis, assesses the condition of the electrolytics after years of service, and decides which parts genuinely need attention and which are simply old.

Recapping uses Panasonic FC and FM series and Rubycon YXH electrolytics, chosen for low ESR and long life ratings at temperature rather than for any audiophile marketing claims. That distinction matters: in an amplifier, the parts that most benefit from replacement are the supply rail reservoirs and the small signal decoupling capacitors near heat sources, since these are the components whose degradation actually appears as hum, poor bass control or intermittent behaviour. Desoldering is handled with a Metcal MX-5200, which shows how much easier bulk board work becomes with sufficient thermal recovery, and a Meterman 37XR is used for measurement checks along the way.

The second half of the job is a usability improvement rather than a repair. Cambridge Audio gave the A4 a clean but unlit front panel, which is awkward in a dimly lit listening room, so 3mm Wurth LEDs are fitted to provide subtle ambient illumination of the controls without turning the amplifier into a light show. It is a good example of a modification that respects the original design intent while making the unit more pleasant to use, and the same approach transfers to many other older hi-fi separates.