Ultrawideband
Response and TIM
As mentioned before,
our ultrawideband design provides frequency response from 1 to 160,000 Hz
compared with conventional narrowband design which typically provides response
from 20 to 20,000 Hz.
This ultrawideband
design delivers audible benefits, including incredibly fast transient response.
Fast transient response is important because it means that the vast complexity
of fundamental tones and harmonics reaches the listener in exactly the same time
relationship as on the recording. Conventional narrowband equipment cannot
reproduce fast transients accurately, causing TIM. The music sounds harsh and
metallic. And the spatial relationship of the various instruments becomes
unclear and vague. which degrades stereo imaging.
Discrete Components
vs. Integrated Circuits
Convntional
equipment also contains components that affect the sound quality. Integrated
circuits, or ICs. They're used to save
space and money - a single, inexpensive IC contains hundreds of circuits on a
chip just 1/4" square. Unfortunately, ICs
prestent compromises. Fisrst, they're
not made to the same high standards as the discrete components we use. And the
circuit density creates a problem, too. With so many circuits in such a small area,
each one is affected by its neighbors as the IC heats up. The result is Thermal
Distortion, another recent discovery. Rather than
compromise the sound of Harman Kardon equipment, we design our audio circuitry
with discrete components rather than ICs. They cost more. But sound noticeably
better.
DC Coupling. One
more way we avoid distortion.
The KH725 is also DC
coupled. Basically, DC coupling eliminates coupling capacitors in the signal
path. This eliminates phasing problems which mask low frequencies. So low
frequency response is tighter, more articulate.
Specially Designed
Phono Stage
One purpose of a
preamplifier is to present signals of uniform strength to the power
amplifier. since turntables provide much
weaker signals than tuners, tape decks and other program sources, preamplifiers
consist of two separate amplifier stages. The phono stage,which boosts
tyrntable signals to the same level as the other sources. And the high-level
stage, which then boosts all signals to a level acceptable to the power
amplifier. Additinally, the phono stage performs another
function. It equalizes the phono signal to match the RIAA curve used in the
record making process.
While other
manufactures roll this curve off below 20 Hz and above 20,000 Hz, we follow the
RIAA curve faithfully even beyond the audible frequency range. By equalizing in
this way. the HK725 produces cleaner, drier, tighter bass. And more transparent
highs. Both our 8-stage
phono stage and our high-level stage incorporate one other desig feature. FET
front ends. These provide higher overload capacity, lower distortion, and
higher signal-to-noise ratio than conventional designs.
Fixed Resistor Tone
Controls.
The HK725 employs
unique fixed resistor pushbutton tone controls rather than the conventional
variable potentiometer ratary controls.
This design feature provides several benefits.
First, and most
important, fixed resistors provide less distortion.
Second, fixed
resistor controls provide defeat positions. This allows the signal to bypass
the circuitry altogether for a less processed, less distorted sound. Most tone
controls even when turned to their neutral position force the signal to pass
through the circuitry, causing distorted sound. Of course if you find it
necessary to tailor treble and bass to your listening room, the twin defeats
allow you to alter one frequency range without affecting the other. And finally, pushbutton tone controls allow
you to duplicate any setting precisely and easily.
Tape Copy and
Monitor Controls
Not only does the
Hk725 preamplifier allow you to copy from one tape deck to another, it allows
you to monitor either one. or if you prefer, you may even listen to the tuner,
turntable or other program source while copying.
Subsonic Filter
A subsonic filter
has been incorporated into the HK725 to remove turntable rumble and the effect
of record warp.
Twelve Wiper Volume
Control
Conventional volume
controls employ rotary controls with 4 wipers. The HK725 volume control has 12.
This extra bit of engineering not only provides a smoother acting, longer
lasting control, but helps lower distortion as well.
Other HK725 Series
Components
The HK725 is just
one component in Harman Kardon's new 700 series of high technology separates.
You can also add an amplifier, tuner and cassette deck from our line. Each conforms to the same design philosophy
and rigorous standards as the HK725
Each provides the ultimate in clean, accurate performance. If you're building a complete component
system that inckludes HK725, you'll want to consider the rest of the 700
series. They were made for each other.
Specifications
Input Sensitivity
Phono
: 2,3 mV/47 kΩ
High
Level : 145 mV/23 kΩ
Frequency
Response: Less than 1 Hz to beyond 150
kHz +0, -1 dB
RIAA
Equalization: ±.2 dB (20 Hz - 20 kHz)
Signal-to-Noise
Ratio
Phono : 90 dB
(IHF-A)
High Level : 106 dB
(IHF-A)
Phono Overload: 250 mV at 1 kHz
Total Harmonic
Distortion
Phono : 0,009%
High Level : 0,005%
Intermodulation
Distortion: 0,009% at 2 volts output
Slew Rate: Greater than 200 volys/microsecond to output
with IHF standard load
Dimensions (W x H x
D): 385 x 73 x 320 mm (15,2" x
2,9" x 12,6")
Weight: 4,2 kg (9,25 lbs)