What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Harman/Kardon HK725

 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.

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)

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