Harman/kardon twin powered specifications

Category : Receiver

Among friends of the Harman / Kardon brand HK for short, the "Twin Powered" series (x30) already enjoys almost cult status, as it marks acoustic experiences (musicality and dynamics, warmth as well as spatial imaging and richness of detail) among discerning listeners for that time, which until then were only known from receivers built in tube technology.

In 1973, HK came up with two receivers, which, as the addition "Twin Powered" indicated, are equipped with one power supply per channel. These two models 630 and 930 were built until 1975. Then followed in 1976 the successors 430 and 730. Production was discontinued in 1977 after the sale to the Silver company. Both series were supplemented by the basic models of the 330 line. Although they didn't have two power supplies, they didn't have to hide their sound either.

In the external appearance, the design was based on the 60s, straight-lined "modern" and without frills in chrome steel and black. In the USA in combination with a wooden case (in Europe as an option). The model series are also similar and are confusingly similar, only a sixth rotary knob and three pushbuttons to the right of the tuning wheel marked the prominent position of the 930. All models shone with excellent power amplifiers with a very wide power bandwidth and linear frequency range, which was marketed as ultrawideband. This technical structure made HK known, among other things, also because of the very deep transient distortions. Furthermore, the "twin powered" devices had a very good phono and tuner part, the latter of which had outstanding features in the 930. When evaluating the output power of the x30 series (2x 25 to 2x 45 watts at 8 ohms / up to 2x 65 at 4 ohms), it should be borne in mind that HK at that time stated very conservative performance data and the 930s can provide up to 2x 100 watts (4 ohms) for short-term signal peaks in the music power (dynamic power).

When quadrofony became a new trend and challenge for manufacturers at the beginning of the seventies, HK also launched another line on the market. Their receivers were also "twin powered" and could be recognized as devices suitable for quadrofonic playback by a + symbol and a "joystick" (with the exception of the 50+) for the four-channel balance of the listening field. So there were the models HK Model 50+, HK Model 75+, HK Model 100+ and HK Model 150+. The power spectrum ranged from about 4x 20 to 4x 45 watts of sine at 8 ohms.

Harman Kardon 150+ front view

Harman Kardon 150+ interior view

While 50+ and 150+ did not undergo any further development, the successors HK Model 800+ and HK Model 900+ were created from the other two models. Although it marked the top of the "+ series" in terms of the power output of the 150+, it was deleted without replacement, as too many copies "burned" due to overheating. A switching option (joint operation of the front and rear speakers = bridging) allowed stereo operation with then approximately 2x 150 watts, as a result of which one of the two power amplifiers was extremely loaded, especially if sufficient air supply was not provided. This is also the reason why, in addition to the already lower number of units sold (high sales price), only a few copies are still doing their job today.

The Klipsch forum is recommended for interested readers, and here in particular the contributions of "HDB Rbuilder", on whose knowledge many of the information provided here are based.

Harman/kardon twin powered