The HK 770 is
certainly one of the most sophisticated stereo power amps you can buy. With 65
watts per channel, and plenty of extra headroom, the HK 770 can easily handle the most demanding
of transients.
Unlike most
conventional amplifiers, negative feedback levels in the HK 770 are kept below
20 dB, reducing TIM distortion to inaudible levels. Also unlike conventional
power amps, the brawn behind the Kh 770 comes from a pair of independent power
supplies. We use two discrete rectifier circuits. Two sets of electrolytic
capacitors. And two massive toroidal transformers, which eliminate the stray
magnetic fields that cause hum.
Our twin power
supply design provides you with two distinct benefits.
First, it eliminates
the possibility of channel-to-channel interference. It also prevents one
channel from draining the power available to the other. Each power supply is
further divided into high and low level stages. This ensures that the power
requirements of the high level stages do not drain current at the expense of
the low level stages
Unlike most power
amps, the HK 770 gives you, accommodations for two pairs of speakers with
independent speaker switching. Plus a power display that allows you to monitor
performance. And for more accuraate power readings at low listening levels,
display aensitivity can be increased by a factor of 10. The HK 770 packs a lot
of power and lot of technology into a surprisingly compact amplifier.
The Harman Kardon
HK770 Stereo Power Amplifier is FTC rated for 8 ohms at 65 watts RMS per
channel, 20 Hz to 20 kHz, at less than 0,03% Total Harmonic Distortion. Test
results were considerably better than even the low claimed distortion,
resulting in some of the lowest distortion figures ever attained from a power
amplifier. The sound quality reflects the low distortion, being exceptionally
clean, particularly in the deep bass. Special construction techniques result in
an unusually small cabinet for an amplifier of this power rating. The front
panel has left and right LED dual range output power indicators calibrated
0,05-100 watts and 0,005-10 watts into 8 ohms.
The LED power output
indications were essentially precise, with a virtually flat 20 Hz to 20 kHz
Frequency Response. An output power hold-off prevents power supply turn-on
transients from being fed to the speakers. One unswitched AC convenience outlet
is provided.
Specifications
Power Output: 65 watts (RMS per channel into 8 Ω, both
channels driven simultaneously from 20 Hz to 20 kHz with less than 0,03%
T.H.D.)
Power
Bandwidth: less than 8 Hz to 100 kHz at
32,5 watts per channel with less than 0,03% T.H.D.
Total Harmonic
Distortion: 0,006% at rated output
Intermodulation
Distortion: less than 0,01% at rated
output, both channels driven at different operating frequencies
Frequency
Response: below 1 Hz to 250 kHz +0, -3
dB
Damping Factor: greater than 50
Slew Rate: 150 V/µsec into 8 Ω at rated power output,
both channels driven
Square Wave Rise
Time (20 kHz): 1,5 µsec into 8 Ω at
rated power output, both channels driven
Square Wave
Tilt: less than 2% at 20 Hz
Total TIM
Distortion: less than 0,007% at rated
output
Total Interface I.M.
Distortion: less than 0,007%
Power Supply
Crosstalk: greater than 100 dB (20 Hz to
20 kHz) unused channel sherted input
Amplifier
Configuration: Twin toroidal
transformers with positive and negative supplies plus high and low voltage
supplies for output and driver stages
Signal-to-Noise
Ratio: 123 dB (IHF-A)
Input
Impedance: 35 k Ω
Sensitivity: 1,2 V for rated output
Dimensions (W x H x
D): 385 x 72 x 320 mm (15,2" x
2,9" x 12,6")
Weight: 10,1 kg (22,2 lbs)