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Separation filters (high-frequency and low-frequency links) are placed on small individual PCBs installed into the side panels of the satellites cases. The coils are of thick wire and there are just a few film capacitors around them.

Our next measurements revealed that the Rz graph (active resistance) is not quite even, however, its value doesn’t drop below 4Ohm. The delta is less than 1dB, the unevenness of the amplitude-frequency characteristics of the acoustic system can be squeezed into +/-3dB.


Amplifier PCB.


5532 - one of the operational amplifiers.


LM3886 output amplifiers use rear metal panel of the satellite case
to dissipate heat.

The amplifier is put together following a classical schematic: using two low-noise operational amplifiers 5532 from Texas Instruments and two LM3886 integral chips from National Semiconductor at the output. 5532 operational amplifier is known for high performance and low level of distortions. LM3886 micro-chip belongs to the “Overture” family and allows obtaining 135W of instantaneous peak power. The harmonic distortion coefficient doesn’t exceed 0.06% in 20Hz-20kHz frequency range. Typical ripple rejection equals 120dB, therefore the integrated circuit design is fairly simple. These characteristics of the IC ensure high-quality sound that is why they are used all over the place starting with boom-boxes and all the way into luxurious high-end. By the way, LM3886 has become very popular in the DIY sector, too, so with the price of only $2 a piece it is being widely used in “home-made” designs also.

As you see, both LM3886 are installed onto the very edge of the PCB. They cool down by dissipating the heat through the rear panel of the right satellite, which also carries all the other electronic components of the acoustic system. So in the end, it warms up pretty significantly.

Next to the output IC on the PCB there are capacitors with maximum recommended capacity of 10000MF (microfarad). They are installed along the power circuit of each channel branch. The maximum calculated power of these channels is 2x25W. As for the schematic peculiarities of the acoustic system amplifier, there are none to talk of.


Power supply unit transformer.

Power supply transformer is screened with copper plates, which helps eliminate the background noise when the amplifier is mounted very close inside the system.

 
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