THE RATIONAL AMPLIFIER, FROM CROWN.
Sound reproduction systems of the 1980's will include "smart" components- components that react to their environment, that know how to protect themselves, and know how to keep functioning in that environment. They belong in your future.
The Crown Distinction SA2 stereo power amplifier is a rational amplifier. It analyzes its own behavior in terms of its immediate environment. It protects itself. It keeps on driving your speakers with power reserves that may amaze you. It's available now.
The SA2 has four on-board computers that constantly monitor and control the performance of the amp.
The SA2 knows when it can use its full power capabilities, and when it has to cut back in order to prevent damage to itself.
The SA2 is sonically so accurate that its distortion and response levels require highly sophisticated test instruments to measure. However you measure them, the SA2 translates into beautiful music.
The SA2 incorporates new system engineering concepts that won't easily be duplicated. It is unique.
SOA-it's important!
The safe operating area (SOA) of a power transistor is defined by the internal temperature of the transistor.
That temperature must be kept below a critical level or the transistor will be damaged, an expensive and bothersome event.
Audio circuit designers have always known that SOA is difficult to measure, since it varies widely de pending on what the transistor is being asked to do. Designers have had to estimate arbitrary limits for output voltage or current in order to protect output transistors, leaving much of the capability of the power transistor unused. Such designs are not as efficient as the SA2 has proven to be.
SOA measured by Crown.
Crown's engineers several years ago developed a special test instrument to accurately measure the changing SOA of power transistors under varying loads. To the best of our knowledge, it's still the only such test equipment in the audio industry.
From the work done on this instrument, Crown developed the mathematics of output device behavior needed to design the computer-con trolled protection system of the SA2 amplifier. That system makes it possible, for the first time, to utilize fully the capabilities of power transistors in an audio amplifier.
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SPECIFICATIONS:
Stereo Output Power: 220 WATTS PER CHANNEL MINIMUM RMS (BOTH CHANNELS OPERATING) INTO AN 8 OHM LOAD, 20Hz-20KHz AT A RATED RMS SUM TOTAL HARMONIC DISTORTION OF 0.05% OF THE FUNDAMENTAL OUTPUT VOLTAGE.
350 WATTS PER CHANNEL MINIMUM RMS (BOTH CHANNELS OPERATING) INTO A 4 OHM LOAD, 20Hz 20KHz AT A RATED RMS SUM TOTAL HARMONIC DISTORTION OF 0.08% OF THE FUNDAMENTAL OUTPUT VOLTAGE.
600 watts per channel minimum RMS (both channels operating) into a 2 ohm load, at 1KHz; rated RMS sum total harmonic distortion of 1.0% of the fundamental output voltage.
Monaural Output Power: 700 WATTS MINIMUM RMS INTO AN 8 OHM LOAD, 20Hz-20KHz AT A RATED RMS SUM TOTAL HARMONIC DISTORTION OF 0.12% OF THE FUNDAMENTAL OUTPUT VOLTAGE.
440 watts minimum RMS into a 16 ohm load, 20Hz-20KHz, at a rated RMS sum total harmonic distortion of 0.08% of the fundamental output voltage.
1200 watts at 1KHz into a 4 ohm load, at a rated sum total harmonic distortion of 1.0% of the fundamental output voltage.
Stereo Hum and Noise: 115dB below rated output, "A" weighted.
Stereo IM Distortion: Less than 0.01% from 0.25 watts to 220 watts into 8 ohms per channel.
Stereo Slewing Rate: Greater than 30 volts per microsecond.
Stereo Frequency Response: +0,-1.5dB, DC-80KHz.
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On-board computing.
The SA2 protected-power system starts with the output transistor data developed by Crown, which is now in computer memory at Crown. Analog computer circuits built into the SA2 are programmed from data about the SOA of the output devices. The on board computers obtain real-time input from sensing devices which re port current, voltage and thermal behavior of the output transistors.
The computers then describe, in real time, what the transistors have been doing, what they are being asked to do, and compute whether the result of all that could drive them outside their SOA.
If the on-board computers predict operation outside the SOA, the out put is limited automatically and immediately. The computers also limit output only to the degree necessary, so that output power is always at the maximum safe level for the existing environment. The limiting is self correcting, and full output power is automatically restored as soon as the demands on the output devices no longer threaten their SOA limits. All this happens in micro-second time, with the output devices being constantly checked.
Continuing safe output.
Output power is never, in the Crown SA2 system, limited arbitrarily. Your SA2 continues at full power as long as output transistor safe operating area is not violated. Where other amps would simply thermal out and shut down, the sensing and protection concepts employed in the SA2 keep the maximum safe power flowing to your speakers under any and all conditions.
Unique heat sink design.
The Crown SA2 heat sinks may be new to most home audio system owners. The finned aluminum channels in these Crown-made heat sinks are much more efficient than castings because they rapidly dissipate large amounts of heat to keep the SA2 at its most efficient thermal level. In addition, a rear-mounted fan keeps a gentle flow of air moving through the amp. If the chassis should heat up, the fan automatically shifts to a higher speed until the amp returns to a cooler operating level.
And much more.
When we designed our rational amplifier, we didn't stop with the innovative protection system. The SA2 is built around a carefully thought out circuit design that contributes to immeasurably low distortion. For instance, a junction field-effect transistor (J-FET) input is incorporated into a multiple feed-back design to reduce noise and distortion while offering perfectly controlled transient response.
The main power supplies and transformers for each channel are separate. The SA2 mechanical design emphasizes sensible weight distribution and easy handling. The Crown IOC distortion indicating system notifies you about deviations in output waveform before any kind of distortion becomes audible. Sub-audio speaker protection is provided by monitoring the output and turning off the affected channel if necessary.
Indicating dynamic range.
You will be pleased at the elegant concept of reporting music peaks in the Crown SA2. The vertical LED meters on the front panel actually display two values for each channel. The top light will always be a peak-hold display with a four second delay. The other light, which may be coincident with the peak -hold indication, but is usually below it, is a running peak indication. The differences between those two will enable you to evaluate the dynamic range available in the music source.
Built by Crown.
The SA2 is a Crown product. If you're new to high -quality audio systems that may not mean much, so we suggest you ask an experienced friend about us. He will tell you about the Crown reputation for reliability, for sonic excellence, for service. We're proud of that reputation, so we work very hard to uphold it.
Crown Care.
Every SA2 is thoroughly tested at the factory, and a certified proof-of-performance report is attached, detailing the measured specifications for your SA2, which are often better than the published specifications.
Every SA2 is also covered by the full Crown warranty, by which Crown guarantees, at no cost to the current owner, repair or replacement of any SA2 which does not perform to original, published specifications for a period of up to three years from date of original purchase. This warranty also covers round-trip shipping for the unit. We believe that this protection for your investment is the finest available anywhere.
We think the SA2 is quite simply the finest audio power amplifier you can buy, one which will expand your musical horizons. But before you make up your mind, you may want more information. You can examine the SA2, and the product manual, at your nearest Crown Distinction dealer, or you can send us five dollars with the coupon and we'll send you an SA2 manual. If you return the manual, we'll return the five dollars.
Listen to the Crown SA2. It's a rational decision.
(Audio magazine, Jun. 1979 )
Also see:
Crown FM stereo tuner (ad, Aug. 1979)
Crown DC300A power amplifier (Mar. 1973)
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