series. Product reviews PCU25 Preamp/Control Unit + A20 Valve Power Amp Gramophone, rev. by Philip G. Tandy, April 1962 Hi Fi News, rev. by George W. Tillett, April 1962 Amateur Tape Recording, rev. by Fred Judd, May 1962 Audio and Record Review, September 1962 400 Range Hi Fi News, 426 Receiver (Amp + AM/FM tuners) rev., by George Goodall, October 1968 500 Range amplifier Hi Fi Sound, review of 521 Amplifier, by Fred Judd, April 1969 Audio and Record Review, review of 521 Amplifier, by Frank Roberts & Donald Aldous, 1969 Luister [Dutch], review of 521 Amplifier by Jan Kool, 1969 Which, Large comparison review including the 521 Amplifier, April 1970 Hi Fi Sound, review of 526, by Fred Judd, May 1970 Hi Fi Sound, 526 included in comparison of 10 tuner-amps, by Fred Judd, October 1920 600 Range amplifier Audio, 626 Receiver (Amp + AM/FM tuners) rev., by Fred Judd, May 1973 Hi Fi News, 626 Receiver (Amp + AM/FM tuners) rev., by Fred Judd, October 1973 Hi Fi Answers, 626 Receiver (Amp + AM/FM tuners) review., December 1974 Luister [Dutch], 621 Amplifier rev., by Jan Kool, November 1973 Hi Fi choice, Receivers 626 Review, by Angus McKenzie, 1976 Issue 2 Hi Fi choice, Amplifiers 621 Review, by Hugh Ford, 1976 Issue 6 Hi Fi choice, Receivers 626 Review, by Angus McKenzie, 1977 Issue 7 Audio (USA), 625 Receiver (Amp + FM tuner) rev. by Leonard Feldman, March 1978 Practical HiFi, 602 Speakers as part of a 'system' rev., by Philip Mount, March 1978 700 Range Hi Fi News, 730/732 Amplifier rev. by Martin Colloms, July 1982 Popular HiFi 730/732 Amplifier rev. by Noel Keywood & Chris Thomas, September 1982 Hi Fi News, postscript to July review, September 1982 References External links UK Hi-Fi History (Armstrong section) Audio equipment manufacturers of the United Kingdom Audio amplifiers 1932 establishments in the United Kingdom