Harman Kardon Citation 21+22 topset 2x200w RMS, geserviced

Legendarische vintage topset uit de gouden Harman Kardon jaren.


Bestaande uit:


Citation 21 voorversterker


Specifications
Frequency response: 20Hz to 20kHz




Total harmonic distortion: 0.005%




Input sensitivity: 0.125mV (MC), 2.2mV (MM), 130mV (line)




Signal to noise ratio: 73dB (MC), 78dB (MM), 84dB (line)




Channel separation: 55dB (MM), 54dB (MC), 56dB (line)




Dimensions: 440 x 90 x 345mm


Citation 22 power amp:


Since the introduction of its first Citation Series audio components in 1963, Harman Kardon has reserved that name for products whose design and performance represent a clear departure from contemporary engineering practices. After an interval of about seven years without any Citation models in its line, the company has introduced a new Citation Series featuring a preamplifier, two power amplifiers, and a tuner. Rated at 200 watts per channel into 4 or 8 ohms, from 20 to 20,000 Hz, the Citation Twenty-Two is currently Harman Kardon's most powerful amplifier.




Much of the basic design philosophy of previous Citation amplifiers has been retained and its execution has been enhanced in the Model Twenty-Two. Among other things, that design philosophy calls for a wide bandwidth (far in excess of the audible frequency range), high instantaneous current-output capability, low overall negative feedback for reduction of transient intermodulation distortion (TIM), and use of discrete semiconductors (instead of ic's) in the signal path.




In designing the Citation Twenty-Two, the problem of dealing with widely varying speaker loads, and the very high instantaneous currents required to drive some speakers under actual listening conditions, was solved in a very simple and direct manner: selectable power-supply voltages.




There are two related but distinct limitations on the maximum instantaneous power output available from a given output-transistor configuration and load impedance. The maximum possible voltage output is determined by the amplifier's internal DC power-supply voltage, which must not be allowed to exceed the transistors' allowable maximum levels. There is also a limitation on the peak current that can be drawn by the load, which also must remain within the transistors' rated operating range. The continuous power output (the product of the voltage and current) and the heat dissipated by the transistors must also be considered, but these are related to long-term operating conditions and are normally much lower than the peak levels.




In conventional amplifier designs, a choice has to be made between the maximum current-out-put and maximum voltage-output capabilities of the amplifier, as they relate to the load impedance. In order to develop 200 watts into an 8-ohm load, say, the maximum voltage must be 40 volts RMS combined with a current output of 5 amperes. For 200 watts into a 4-ohm load, only 28.3 volts is required, with a current of just over 7 amperes. If, however, a 40-volt maximum output is delivered into 4 ohms, the load will draw 10 amperes, corresponding to 400 watts- well beyond the amplifier's design limits and probably those of the speaker as well. On the other hand, if an amplifier designed to drive 4-ohm loads to 200 watts is terminated in an 8-ohm load, it will only be able to supply 100 watts output.




In order to deliver its rated power output into either 4- or 8-ohm loads, the Citation Twenty-Two has a rear-apron switch to select between two power-supply voltages. The higher voltage provides the rated output into 8 ohms, and the lower voltage provides the same power into 4 ohms without overstressing the transistors or power-supply components, so that the amplifier can operate under optimum conditions with either of the two most common speaker load impedances without compromising either safety or performance. Although some speakers are rated at 5 or 6 ohms, and the impedance of almost every speaker will vary widely throughout its frequency range, there is no need for a critical match. The worst penalty of operating the amplifier in its 4-ohm setting with an 8-ohm speaker will be a slight (and unnoticeable) reduction in maximum power output.




The problem of supplying large short-term peak currents was solved in the Citation Twenty-Two by conservatively designed output stages, each using eight 130-watt power transistors, and by eliminating the usual current-limiting circuits whose operation can cause distortion. The amplifier's maximum steady-state current is effectively limited by the available power-supply voltage, but, according to Harman Kardon, it can deliver peak currents of 100 amperes into either impedance.




The Citation Twenty-Two actually consists of two separate amplifiers, one for each channel, sharing only the power cord and the chassis. The filter capacitors of each power supply are located close to their associated power transistors, so that the peak energy demands of the amplifier can be met with minimum loss through the connecting wiring. The speaker-output connectors are of a unique design intended to make a positive, long-lasting electrical contact between their gold-plated surfaces and the ends of the speaker wires.




The amplifier employs completely symmetrical circuitry from its input jacks to the speaker outputs. The open-loop bandwidth is very wide, to reduce phase shift within the audio band, and the inherent distortion of the circuits is kept very low. As a result, the overall negative feedback is only 12 dB, effectively eliminating transient distortions.




Besides being able to deliver 200 watts per channel into either 8- or 4-ohm loads, the Citation Twenty-Two can be bridged to form a mono amplifier rated at 400 watts into 8 ohms. The all-black chassis measures 17-3/8 inches wide, 14-1/4 inches deep, and 6-1/8 inches high, and the amplifier weighs about 37 pounds.




A lighted power switch is the only front-panel operating control. Narrow red lights indicate the selected impedance mode and tell when the protection circuitry is in operation. A display of eight pairs of green lights shows the amplifier's output level for each channel, in watts from 0.002 to 200 and in decibels relative to 200 watts (0 to -50). A button switches the display on and off, and another changes its sensitivity to match either 4- or 8-ohm loads. On the rear apron are the speaker-output connectors, the audio input jacks, and the switches to change the power-supply voltage and bridge the two channels for mono operation. Price: $895.
















Lab Tests




After an hour of preconditioning at one-third rated power, the top plate of the Citation Twenty-Two was quite warm, but it never became uncomfortable to the touch during our high-power testing. We made all our power and distortion measurements using both impedance settings.




As claimed, the amplifier's power output at clipping was almost exactly identical into 4- and 8-ohm loads (using the corresponding switch settings). The 1,000-Hz waveform clipped at 232 watts, corresponding to a clipping headroom of 0.64 dB. When we drove an 8-ohm load using the 4-ohm amplifier setting, the power at clipping was 145 watts, and into 2 ohms (for' which the amplifier is not rated) it was 312 watts. With the switch set for 8-ohm operation, the 4-ohm clipping output was 352 watts (we did not try 2-ohm loads in this mode).




With the load matching the amplifier setting, the dynamic output during a 20-millisecond burst was 315 watts into 8 ohms and 325 watts into 4 ohms, corresponding to dynamic headrooms of 2 and 2.1 dB, respectively. We also made dynamic power measurements into 2 ohms, measuring 595 watts and 552 watts, respectively, for the 8- and 4-ohm settings. Although the dynamic headroom of the amplifier was considerable, its "power envelope" decayed fairly rapidly, reaching or nearing its continuous value in less than 100 milliseconds.




We measured the frequency response of the amplifier from 5 Hz to 500 kHz. It was down only 0.1 dB at the lower limit and 0.6 dB at the higher frequency. The slew factor, however, was lower than we usually measure on amplifiers whose frequency response is rolled off above the audio range: a factor of 8 with the 4-ohm setting and 6 with the 8-ohm setting. The amplifier was stable with reactive loads simulating "difficult" speakers, with some 60.000-Hz ringing appearing on a 10.000-Hz square-wave output. Its reactive-load factor was 0.64 dB at 63 Hz.




The amplifier's distortion characteristics were excellent and quite similar for its two impedance settings. Typically, the distortion at rated power was between 0.015 and 0.02 percent from 20 to 10,000 Hz, rising slightly to about 0.025 or 0.035 percent at 20,000 Hz. At half and one-tenth power, the distortion was between 0.006 and 0.01 percent over the full frequency range. The 1,000-Hz distortion was about 0.005 percent at a 1-watt level regardless of the impedance settings and the actual load, and it increased smoothly to the range of 0.01 to 0.02 percent with outputs between 10 watts and the clipping point.




The input sensitivity for a 1-watt reference output was respectively 54 millivolts and 77 millivolts for the 4- and 8-ohm settings, and the A-weighted noise level was -99 to - 100 dB referred to 1 watt.




Comments




The Harman Kardon Citation Twenty-Two conveys a visual impression of solid construction and thoughtful attention to detail, and its performance confirmed that impression. As our measurements show, its dual-voltage power supplies give the amplifier precisely the ability claimed for it-virtually identical performance into loads of either 4 or 8 ohms. It was also gratifyingly free of the minor annoyances that sometimes mar the total performance of powerful amplifiers. It was as silent acoustically as it was electrically (no humming or buzzing transformers, no fan noise or clicking relays).




The power-level display, informative without being gaudy (and it can be turned off if desired), appeared to be about as accurate as such an indicator can be. We also noted that the red overload lights were very accurate, lighting just as the waveform was about to clip rather than requiring actual audible clipping.




We were especially impressed with the Citation Twenty-Two's protection system. Designed to prevent damage to the amplifier, which it did to perfection, it showed no tendency to interfere with high-level program peaks. We found that inadvertent output short circuits silenced the amplifier (and lit the red indicator light) until a few seconds after the condition was corrected; then it returned to life as silently as it had turned off. At no time was there an audible click from a relay or a sound from the speakers other than instantaneous silence or the restoration of the program. Heartened by the amplifier's handling of accidental faults, we tried some deliberate misconnections that would have destroyed some otherwise good amplifiers we have used. The Citation Twenty-Two took them in stride.




As for sound-well, driving the amplifier directly from the outputs of a CD player having its own level control, we played a number of CD's noted for their wide dynamic range through several speakers in different power and price ranges. The results were all we could have hoped for, and they clearly demonstrated the benefits of using a powerful amplifier even for moderate listening levels. It was surprisingly easy for a program whose average level remained under 0.2 watt to light the red clipping indicators momentarily without sounding uncomfortably loud. With the CD player on pause, we could hear absolutely no sound from the speakers even with an ear pressed to the grille.




Much the same results could be accomplished with other 200-watt amplifiers. Few others, however, could match the overall silence and smoothness of the Citation Twenty-Two or its virtually bullet-proof design and construction. In spite of our strongly favorable reaction, we do have one criticism of the amplifier's mechanical design (which has nothing to do with its sound quality). Its speaker-output terminals are unlike any others we have ever seen, and we suspect that most people, like us, would be unable to discover how to make the connections without referring to the manual. The terminals will accept only the stripped ends of speaker wires. No lugs, banana plugs, or other common wire terminations can be used, and many special speaker cables cannot be adapted easily (if at all) to these unconventional binding posts. Fortunately, connection is a simple process once you read the manual!




In short, the Citation Twenty-Two looks to us like a winner. If more than 200 watts per channel, exceptional protection against damage, complete freedom from idiosyncrasies, and overall top-quality performance are sufficient for your needs, this amplifier should be an ideal choice




Specifications Power output: 200 watts per channel into 8Ω (stereo)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.08%
Damping factor: 100
Input sensitivity: 1V
Signal to noise ratio: 90dB
Dimensions: 443 x 155 x 398mm
Weight: 20.5kg




Deze zwaar onderschatte eindversterker is recent professioneel gereviseerd


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