Harman Kardon HK 990 Integrated Amplifier Modification

A year ago, we bought the new Harman Kardon 990 Integrated Amplifier. It has 150 watts at 8 ohms and 300 watts at 4 ohms (our single-driver speakers are 4 ohms). Not long after we bought it, we began trying to find ways to modify the amp. Not that we were displeased with the stock, unmodified sound of the amp, which was clear and detailed. The bass was textured and substantial. But based on our experience, we knew the 990 could sound even better. As is often the case with unmodified amps and receivers, we felt the bass could go down lower and that the highs could be extended. The top end was a little harsh, and we felt that there could be more air and top-end bloom. But given the amp’s basic sound and characteristics, we felt that the 990 could be modified into a very special-sounding piece. It would take a year for us to discover everything we needed to do in order for this amp to really open up to its full potential.

We could have advertised our 990 mod earlier in the Christmas season, but we wanted to unlock every bit of sound there is, even though amp’s sound a month ago would have been a big improvement over the stock sound. However, this is the way we have always operated. We believe in giving people the full value of the sound and music that they are paying for, because every improvement, even a small one, makes a big difference in what the listener feels and hears. One of our goals is always to have the listener of our products and modified pieces be not just satisfied but amazed at what he’s hearing.

Finally, a few days ago we heard the sound that we knew this amp could have. It has taken us a year, but now the modified 990’s bass is even more textured and substantial yet still tight. The bass is also darker and more deeply extended, with power and slam at the very bottom. The amp is now very transparent and detailed without being harsh. There is much more air and bloom. The soundstage is huge and very wide. It is also now very immediate and dynamic, capturing previously hidden nuances of voices and instruments. We have listened to quite a number of amps, including those that cost tens of thousands of dollars, and to this point, we have yet to hear and amp that matches the sound performance of our modified 990. In 2007, we had our modified HK 3480 reviewed by John Johnson, editor of Secrets of Home Theater and High Fidelity, who was amazed at the sound that came from the HK amp, which cost only a few hundred dollars. You can read the full review at http://www.hometheaterhifi.com/volume_14_2/hk-3480-receiver-daves-5-2007-part-1.html

We have never had a modified piece returned from an unsatisfied customer. Our regular modification price is $350, which includes shipping in the continental US. For the HK 990, a $450 modification price turns a very, very good stock amp (especially for the price) into one of the great performing amps that will compete with and beat amps that cost tens of thousands of dollars.

Specifications

Description:Solid-state two-channel integrated amplifier with analog/digital inputs, tone controls, bass management, and system equalization. Line-level analog inputs: 6 pairs single-ended (RCA), 1 pair balanced (XLR), processor HT bypass (RCA), 2 subwoofer (RCA). Phono inputs: 1 moving-magnet, 1 moving-coil. Digital inputs: 2 optical, 2 coax, 1 HRS. Line-level analog outputs: 2 L/R, 2 subwoofer. Digital outputs: 2 coax. Output power: 150Wpc into 8 ohms (21.75dBW), 300Wpc into 4 ohms (21.75dBW). Line-level input sensitivity: 350mV. Line-level input impedance: 43k ohms. Phono input sensitivity: 10mV (MM), 1mV (MC). Phono input impedance: 47k ohms (MM), 100 ohms (MC). Frequency response: 10Hz–170kHz, +0/–3dB at 1W; 20Hz–100kHz at half power. Signal/noise ratio: 109dB (line), 75dB (MC), IHF-A (–3dB). THD, both channels driven: <0.03%, 20Hz–20kHz, at 150Wpc (8 ohms); <0.3%, 20Hz–20kHz, at 300Wpc (4 ohms).

Price for the stock HK 990 varies between $1,800 and $2,000 depending on the distributor.

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