Harman/kardon Twin Powered

Among friends of the brand Harman / Kardon the "twin powered" series (x30) enjoys almost a cult status, it marks among demanding listeners for the time acoustic experiences (musicality, warmth richness of detail, dynamics), which until then could be expected only from receivers built in tube technology. It was 1973, when HK came up with 2 receivers, which, as the addition "twin powered" indicated, were each equipped with 1 power amplifier per channel. The 630 and 930 series were built until 1975. Then followed in 1976 the 430 and 730 series, whose production was discontinued in 1977. In the outer appearance the series were similar to each other almost to the confusion, only a 6th rotary knob as well as 3 push buttons on the right of the tuning wheel marked the prominent position of the 930. All models shone apart from the excellent output stages with a very good phono and tuner part, whereby the latter possessed outstanding characteristics with the 930. When evaluating the output power of the x30 series (2x25 to 2x 45 watts), it should be borne in mind that HK gave very conservative performance data at the time.

When in the early seventies quadrophony became a challenge for many manufacturers of consumer electronics, HK also launched another line. Their receivers, too, were "twin powered" and, as units suitable for quadrophonic reproduction, were recognizable by a + as well as a "joystick" (with the exception of the 50+) for balancing the listening field. So there were the 50+, 75+, 100+ and 150+ models. The power ranged from about 4x 20 to 4x 45 watts. While 50+ and 150+ did not undergo any further development, the other two models gave rise to the 800+ and 900+. File:150- front view.jpg

Although in terms of power output the 150+ marked the top of the +line, it was dropped without replacement as too many examples "burned up" from overheating. A circuit option (common operation of the front and rear speaker = bi-amping) allowed stereo operation with almost 2x 150 Watt, which put an extreme load on one of the two power amplifiers, especially if sufficient air supply was not provided. Picture:150- power amp view.jpg

This is also the reason why, in addition to the already low number of units sold (highest selling price of the +series), only a few are still in service today. For interested readers the Klipsch forum is to be recommended and here in particular the contributions of "HDBRbuilder", on whose knowledge many of the data given here are based.