Harman/Kardon HK 705 cassette deck

The Harman/Kardon HK 705 is the first available cassette recorder that incorporates the new Dolby HX "Headroom-Extension" system. The HX process extends the high-frequency overload capability of a Dolby-B equipped cassette deck during reocrding by reducing both the record bias and equalization at those moments  when strong treble content  in present in the music. By lowering the bias, the high-frequency capacity of the tape is enhanced; though this is at the cost of some increase in low-frequency distortion, this distortion is less than would be generated by treble overload - saturation.

HX- processed tapes are playback-compatible with all Dolby-B recorders, and the claimed benefits in high-frequency headroom are roughly equivalent to those porvided by the new metal-tape formulations.

The HK705 is a slim, front-loading deck that uses a single Sendust record/playback head and a capstan driven by a DC servo-motor. A second motor is used to pull the cassette inside the deck after it is laid onto a tray that pops out from the of the unit when the eject button is pressed. When the cassette is locked into place, an angled miror permits viewing the amount of tape remaining on a side through a window in the entry slot. Access for routine cleaning is provided by a removable tab on the top of the deck.

Control of the tape motion is provided through a series of mechanically interlocked piano-key levers.  A Record Mute button is provided for inserting a quiet space between selections, and a Tape End  light begins to blink when approximately three-digit  counter contains a "memory rewind" feature that works with the zero setting,permitting quick return to a selected spot on the tape.

Twelve peak-reading  LEDs per channel form the vertically oriented level indicators, which are calibrated from -20 to +8 dB with the 0 dB point marked as Dolby level (200 nWb/m). A vertical row of pushbuttons adjacent to the LED indicators provides bias and equalization switching for four tape types; Metal, cr02 Ferrichrome and Ferric. Additional front-panel pushbuttons are provided to insert a  subsonic (below 20 Hz) filter and to activate either the regular Dolby noise reduction system or its HX version. These latter two buttons are illuminated.

The large record-level control uses concentric knobs to permit independent adjustment of the left and right channels. An output-level control, which affects both channels equally, also varies the level at the headphone jack, one that is designed to accept headphones with 8 Ω (or higher) impedance (660 Ω) mikes. The rear panel of the HK 705 has phono-jack input and output connectors, an FM-multiplex switch, and a ground post.