Considered by many to be one of the best British valve amplifiers of the mid 1960s, the Radford STA-25 is certainly one of my favourites. It utilised EL84s in the output and was rated at 36 watts per channel (at 1% distortion) and 25 Watts per channel (0.1% distortion).

The STA series of amplifiers (and there were a few of them) were constructed on a welded steel frame and finished in a light dove-grey enamel . At either end of the chassis were large chrome handles which facilitated lifting (these amplifiers were heavy brutes, weighing 36 lbs or 16.36 kg). The handles also served to protect the valves and to enable the amplifier to up-ended without damage for servicing. A large central chassis (covered with a grey steel ventilating grille) contained the two output transformers, power transformer and choke, as well as the power supply capacitors.

Radford incorporated some new feedback circuit design to give this amplifier extremely low distortion and high stability ( less than 0.15% IM distortion at rated power).

For a more detailed description of this unit, please read the vintage test report.

Priced at £52 10s when new, an ST-25 in good condition both cosmetically and functionally today can fetch up to £600 in the UK; with matching pre-amp and tuner expect to pay at least £800.

In 1984, a "Renaissance" version of the STA-25 (mk IV) was created by Radford's new owner, Sondex Ltd, using Radford transformers and KT88 output valves in place of the original EL84s. This originally sold for £499, about the same price as an original STA-25 sells for today.

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