Review: Harman Kardon HK990 Amplifier


Category: Amplifiers

It's really great to have an amp driving the AR9's again that doubles down on power. When the 9's were new, I biamped them with a pair of high current amps which doubled down, but time eventually did what it does to all amplifiers, and since then I've had several pairs of amps which made the 9's sound dull and boring. Once I had 1000w per tower with a pair of high current amps which doubled down and even then the 9's fell flat--not in a good sense. I told myself that time was wearing down the 9's like it did the amps--that the crossovers were getting tired. Or maybe the loss I was experiencing was actually my youthful imagination. Maybe the 9's never were commanding speakers that could talk a throaty, articulate musical language except in my youthful imagination.

Now with the HK990 I have the second amp that doubles down and the first one I don't need two of to drive the 9's, which are so full of sound again that they seem taller than their 4' ll 1/2" towers. They are even overful so that the transcients leap out of them; and they talk again. A friend who goes all the way back with the 9's said, "you'd never guess they aren't biamped". The HK990 is a beast which, inspite of the speakers' demands on this amplifier, runs only very, very warm--not hot.

The HK990 is an atypical integrated amp because the control amplifier is an active gain stage as stated in the owner's manual with its own voltage supply, and this integrated has the robust sound of separates where the preamp is an active gain stage. The preamp and power amp sections are not connected externally with bad-sounding U jumpers that need to be replaced with costly IC's. The switching is internal, and to access the power amp section you simply connect an external preamp to the "processor" input and select said source button on the front panel or remote. All six inputs have an adjustable "gain" feature so that switching from one source to another can be adjusted for consistency in output level. Set at zero gain, the power amp demonstrates only moderate gain. The more the gain in solid state amplification, the more the distortion; and the HK990 has the healthy sound of a power amp with only moderate gain. However, the preamp set at zero gain seems to have too much gain--seems to drive the power amp too hard, although when the HK990 drives higher impedence, less demanding speakers, the negative effects of this higher gain would diminish or maybe disappear. But when I trim the gain as much as possible, the sound quality is superb, and you can play with this feature to find the sweet spot. The gain feature significantly contributes to the amp's agility not only because it can eliminate irritating changes in sound level among various sources but also because it can be used to achieve optimum performance.

The HK990 left my highly regarded preamp and $400 DAC in the dust. I'll just say that's because of RLS 1V (Real-Time Linear Smoothing) because that's the easy, simplistic answer, although I'm sure there are plenty of other reasons, among them being that it's a bit of a hurdle to outperform the current $400 DAC's but surely not one too high for HK. RLS is a device that improves linearity at the point where the digital signal is converted to analogue and normally found only in high end professional equipment. Joe at HCGconsumergroup (Harman Kardon) has informed me that RLS is "not usually found in 'consumer' type products". Compared with my reference preamp and DAC, highs are open and smooth; bass is hard-hitting and thundrous, bass extention could hardly be improved.

Add to it the companion HD990 CD player with HRS Link and you can tweak the sound quality even more. HRS Link is an optional output on the CD player which locks onto the HK990's external clock to illiminate jitter using a cable that is included with the HD990 and that uses a standard RJ45 "network" connector. It is proprietary and is found only on Harman Kardon and Mark Levinson components per Joe. Using a reference digital cable which I connected to one of the HK990's inputs, I compared a digital input signal with and without HRS Link. First impression was that something was missing in the sound with HRS Link. The unconsious mind apparently processes jitter as a part of the music, and with HRS Link there is less quantity of sound so that sound minus jitter equals a purer sound. I found one review which claimed HRS Link to be definitely superior and one which could hear no difference in the several outputs of the HD990. These inconsistencies might be explained by the differences in other components--namely speakers and cable--or the room. Adaquate break-in is of course important as well previous to any critical listening. You will know when the HK990 has turned the corner on break-in. With this amp, break-in is dramatic.

The HK990 pretty much succeeds in being all things to all users. It features optional balanced imputs, optional "Direct Path" which minimizes switching in the analogue inputs, two sets of speaker terminals connected in parallel with a load warning, and a detachable power cord absent the ground termination but which accepts an EIAC power cord. It features optional tone controls, subwoofer outs with bass management, and room equalization as well. It includes an AD converter and phono section with MM and MC inputs. No USB port.

The HK990 does have one quirk that I haven't experienced with any other amp. When an appliance or a light switch is turned on, it cuts out for a split-second. Joe at HK said he's only heard of this issue from me and from his own experience with another model HK amp. His amp exhibited this behavior after he moved from one house to another. He resolved the issue by connecting the amp to another circuit, as I also did. Other possible solutions that come to mind are a dedicated circuit or a power conditioner with a storage capacitor, a feature absent in my entry level power conditioners. But the amp is so good that I would live with this anomaly.

The sound quality of the HK990 puts it deep into high end territory and makes it an extraordinary value. The extraneous components and features all in one box are just the bonus.

Lynne Arnett

CD's: Yellow Jackets, Time Squared; Flim & the BB's, Tricycle Gold; Don Dorsey, Beetovan or Bust; Yes, Fragile (MFSL); Dave Matthews Band, Crash; Norah Jones, Featuring..; Various Artists, Funky Organ; Dire Straits, Dire Straits; Holly Cole Trio, Don't Smoke in Bed; Johnny Cash, The Essential Johnny Cash. Cat Stevens, Cat Stevens Gold.

Associated gear
HD990 CD player
Acoustic Research AR9 (1978-1982)87db
SPL, 400w continuous
Anti-cable by Paul Speltz

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In regard to the companion cdp HD990, if you haven't bought it, I probably would not. I'm sure the electronics are high quality; the problem is that the machine is so light and that includes the transport. I'm using an old hk cdp that was made between 1988-92 as a transport. The HD7600 and mk11 are 20 pounders with solid transports, and I use the hk990's onboard DA converter which is high quality. Switching out the hd990 for the hd7600 and using the hk990's DA converter was a significant upgrade.

You need a heavy solid transport the variable being the quality of the circuitry which transmits the digital signal.
I purchased an HK 990 about two weeks ago. It has definitely changed the sonic signature of my system for the better. Previously I was driving a pair of Usher Dancer Mini loudspeakers with a Cambridge Audio Azur 840A v2 amp. I received an HSU ULS-15 subwoofer for Christmas, but was never able to integrate it into my system to my satisfaction, as my crossover options were limited to running the Ushers full range and attempting to fill in the frequencies below that with the sub. It went low, but not clean enough. It became obvious to me that I needed some type of bass management system, but I cringed at the idea of replacing my amp with an AVR. Then I stumbled upon the HK 990. Dual mono configuration producing 150W per channel (seems like more). Best of all it had what no other stereo amp that I was aware of had......bass management. I bought one.
First of all let me say that lifting a dead donkey would be easier that picking up this amp! The damn thing is heavy! I wrestled it into my rack and replaced my DacMagic with a toslink cable going straight from my music server to one of the optical inputs on the HK 990. I then set the HK 990 to crossover my speakers at 80HZ. The change was immediately noticeable. The bass was cleaner and actually seemed to go lower than before. But, what I didn't bargain for was the improvement in the upper registers as well. With the DacMagic/CA 840A combination, the focus seemed to be on the treble. With the HK 990 the mid-range became slightly more prominent. I guess the term audiophiles like to use is "sweet". Listening to Beethoven piano sonatas, I noticed a realistic percussive property to the leading edge of each note that I have never noticed before. I've only had this amp in my system for a little over a week, but I already love it. With four digital inputs, lots of analog inputs, bass management and oh yeah.......room correction software, all packed into a box that produced over 150 watts of super clean power. What's not to love?
Cool! I've got my crossover set at 40hz especially because I made a bad decision and am now stuck with a pair of Paradigm PDR10's. They are so pathetic that they wheazed once and I'm afraid I will destroy them. The power light dims also when they get a heavy drum. But the current set up is working quite well.

How do you like your sub? I need to sell mine and replace at some point.
The HK 990 is now discontinued. I wonder if there's a replacement in the works.