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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