Amplifier on STK402-020… STK402-120

Today I would like to tell you about the amplifier which, in my opinion, is an excellent solution in terms of price-power-quality. And so, in the main role we have today the chip series STK. Chips stk - hybrid chips that are made on unpacked transistors for thickly film technology and laser adjustment of the values ​​of all resistances. I, like a fairly large number of radio amateurs, consider these amplifiers to be one of the best and bypassing the well-known TDA and LM in sound quality. Of course, we can also recall tube amplifiers, but this is a rather vague subject, and besides, today it becomes not only easy to find standing lamps and transformers, and if it is possible, the prices for such exhibits are not the lowest. As for the microcircuits, they only gain a turn and, it’s easy to find the necessary details of the strapping to them. If you dig deep into the industry and consider the range of microcircuits that most companies install on their sound-reproducing devices, then you can see the entertainingtrend, for example, if you consider almost any acoustic system of the budget level (1000-2000 rubles.) then at best you will find there tda7294 or tda2050. Manufacturers have resorted to this solution because the chips in this series are not picky about the power supply, they require an extremely small amount of external strapping (resistors, capacitors, coils), and sometimes they do not require it at all. If you try to consider more expensive and high-quality speakers, in most cases you can see either transistor amplifiers or the very same STK. In this article we will look at the STK402-120S chip. One of the advantages of the “STK402-020 ... STK402-120” line is that each of these chips has exactly the same strapping, and the last value (..120) denotes the maximum power that This microcircuit is able to provide (120W). So everyone can choose the power that is needed for him, and if it stops it will be enough to replace only the chip with a higher voltage and, in some cases, a power transformer for a higher voltage. And so I think it's worth changing over practice and we will start with the parameters of alllineup:
 Amplifier on STK402-020 ... STK402-120
And the characteristics of our specific amplifier:
Amplifier on STK402-020 ... STK402-120
After the announcement of all the characteristics, I think you can proceed to the assembly. And the assembly is supposed to start with the power supply. It uses a bipolar power system or as it is also called mid-point power. Here is the diagram of our power supply:
Amplifier on STK402-020 ... STK402-120
In this type of power supply unit there is a minus and a plus and a ground (( housing). The voltage specified in the parameters namely + -39 V is the voltage that should be between plus / minus and ground ie between the plus and minus should be 78 V. Then consider the circuit of the amplifier itself:
 Amplifier at STK402-020 ... STK402-120
Weekend resistors at 0.22 ohms and 4.7 ohms should have a power of at least 2 watts, the rest can be taken at 0.25 watts. Also, the maximum voltage of electrolytic capacitors at 100 and 10 microfarads should be higher than the supply voltage. Well, now I think you can proceed to the assembly.I was partially lucky and got into the hands of an old stereo from which not a small part of the details was borrowed. Again, let's start with the power supply. This was the main part that I borrowed.
Amplifier on STK402 -020 ... STK402-120
The transformer gave out + - 50, but this is completely within the allowable parameters of our microcircuit. There was only one problem .. Since the smoothing capacitors were on a different board, they had to be soldered and their own board was made:
 Amplifier on STK402-020 ... STK402-120
Then it is worth taking up the amplifier itself, since there are too many elements about wall mounting (as is the case with the TDA) there can be no question. And so here are the photos of the amplifier assembly:
 Amplifier on STK402-020 ... STK402-120
Amplifier on STK402-020 ... STK402-120
Amplifier to STK402-020 ... STK402-120
 Amplifier on STK402-020 ... STK402-120

 Amplifier on STK402-020 ... STK402-120

Here is the final photo,so that I don’t have any questions, I’ll say right away that most non-polar capacitors in this case are in the same cases as resistors. Everything else in this photo lacks two output resistors of 4.7 ohms. At this most of the work came to an end, it remains only to remove all the components in the case and attach the chip to the radiator. In my case, I decided to use the same package from the music center.
 Amplifier on STK402-020 ... STK402-120
 The amplifier on the STK402-020 ... STK402-120
Amplifier on STK402-020 ... STK402-120
 Amplifier on STK402-020 ... STK402-120
Amplifier on STK4 02-020 ... STK402-120
If the whole circuit was soldered correctly and the correct power was supplied, then the amplifier will start working immediately without any settings. And in the end we got a fairly high-quality amplifier that could well satisfy the need for powerful and high-quality sound. I think many, like me, after using amplifiers on STK, are unlikely to return to TDA or LM.

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