Integrated Amplifiers

Harman Kardon HK 990 Stereo Integrated Amplifier with Digital Room Correction and Dual Subwoofer Bass Management – Part I


What Makes the HK 990 Unique?

When I am asked to select electronics for a new stereo system, I often surprise the questioner by recommending an AV receiver. AVRs have digital-signal processing (DSP) chips which, among other things, do room correction and advanced bass management. AVRs take digital data directly in from a CD player and, after passing it through the DSP, send data directly to an internal digital-to-analog converter (DAC). The analog signal emerging from the DAC is inches from the power amplifier. No analog cables are required. The analog signal from the DAC output must pass through the volume control before it sees the power amp. In a traditional stereo preamp or integrated amp, the volume control is a mechanical device with an unreliable wiper pressing on a piece of carbon. An AVR resolves the reliability issues of the potentiometer because it is a digitally-controlled device integrated circuit (IC). The potential divider uses a tapped integrated resistor, and the desired tap is selected by a CMOS switch. The digital aspect also enables the balance function to be accomplished concurrently. Balance is feasible since each channel's digital control value is different. At high frequencies, mechanical balance controls are often the primary source of reduced channel separation, a problem not associated solid-state devices. Tone-control functions are embedded in the DSP, obsoleting analog electronics (formerly associated with loading the main signal path), mechanical switches, and mechanical controls.

The overhead of an AVR for stereo can be costly: one is paying for stuff they are not using, including five power amplifiers, five DACs, and five digital volume controls. Obviously, cost savings are squeezed across the analog section to keep the price reasonable when seven, rather than two, channels of analog electronics reside in the box.

The video switching and up-sampling circuitry may represent half the price of an AVR, but have no utility for a stereo music system. Some functions of the DSP processing (e.g., Dolby and DTS loss-less multichannel coders, surround sound synthesis, and five additional channels of room correction filters) offer no value for stereo; so, you are paying for more DSP than is needed. Last and definitely least, a TV is required to access the AVR's setup menus, which are not accessible from the front panel. Obviously, the rear panel is simplified with no video I/O's and only two channels coming in and out.

An ideal setup for the stereo enthusiast would have the AVR manufacturer jettison the superfluous stuff, upgrade the analog section, and alter the configuration of the front so setup adjustments can at the front panel, not on a TV screen. I have asked every manufacturer who sells AVRs and traditional analog stereo products when they will adhere to this roadmap; "never" is typically the answer on the belief sales volume will not justify the costs of re-engineering.

Harman Kardon must have had an epiphany for they are introducing the HK 990. The target market is high-end analog integrated amplifiers, not traditional stereo receivers; hence, the $2500 price tag. At that price, state-of-the-art analog and digital components are de rigueur.

The HK 990 shares the EzSet/EQ II digital room-correction system with the top-of-the-line $2500 AVR 7550HD as well as its bass management system for two subwoofers. Other current Harman Kardon AVRs use a simpler system.