Making the ample amplifier, Class A Power Amplifier
Keywords: power amplifier, HiFi, power amplifier
Many enthusiasts are willing to make amplifiers, but most of them are limited to some single-chip integration, such as LM1875, LM3886, LM4766, TDA7294, etc., using these ICs, their sound quality is better than in the market, low-end amplifier, but with some high-end Hi- Fi power amplifier is compared to sound quality still have a large gap. Here is recommended to make a wide range of boosted category A power amplifier circuits for reference. Its composition block diagram is shown in Figure 1.
The circuit has the following characteristics: 1. The block is combined with a block, which can be appropriately or decreased according to its own economy. 2. Most of the voltage amplifies most of the electrical amplifier, easy to use high and low-pressure two sets of power supplies, which can choose a number of characteristic post-level circuitry, which is also easy to install a fixed heat sink, which is convenient for fever. 3. With no large ring negative feedback design, the effect of speaker negative feedback electromotive force on sound quality can be further improved.
Limited to the space, here is the introduction of the voltage amplifies most of the current. The following is a two-channel design, only a schematic diagram of a channel, another channel, power supply and protection circuit diagram slightly. First, most of the voltage amplifies
Use the finished plate provided by the manufacturer. The panel double-channel design uses a double-sided gold-plated circuit board, a large number of fever devices on the board, such as the five-ring metal film resistance, ELNA fever capacitance, audio special high-frequency tube, low noise constant stream dedicated field effect tube. The schematic diagram is shown in Figure 2. Use the twin field effect tube NPD5565 input, using a common-source co-based circuit, active load and differential circuit, compared with the voltage amplification module circuit of the Mantiss Company's HDAM module circuit and some domestic manufacturers, this circuit seems to be designed more tends to The voltage amplifier can be wider, ± 35V ~ ± 60V can work, and it is recommended that the voltage amplifier is supplied with a parallel regulated power supply and is 5V to 10V higher than the current amplifier. Improve, sound quality is also more ideal.
Second, most of the electricity
There are a variety of current amplifier plates to match the above-mentioned electrical pressure, and the following table lists the reference of the partial parameters of the power tube to provide enthusiasts.
1.2sk2013 / 2sj313 Push 3 pairs 2SK1529 / J200, the schematic is shown in Figure 3. 2.2SK2013 / 2SJ313 Push 3 pairs of 2SC5200 / 2SA1943, the schematic is omitted, and the K1529 / J200 can be changed to C5200 / A1943 when assembled. 3.2SC5171 / 2SA1930 pushes 6 2SK851, the schematic is shown in Figure 4, and the ultra-large current MOS field effect tube 2Sk851 has the characteristics of fast switching speed, low conduction resistance, low distortion rate. At present, there is still no matching pairing, the circuit uses quasi-complementary output, and 2SK851 has used in Tianlong PWA-2000N amplifier amplifier. 4.2SC5171 / 2SA1930 pushes 6 2SD1037, the principle drawing, can refer to FIG. 4, when assembled, simply change the K851 to D1037. The circuit uses quasi-complementary output, as long as it is designed, the quasi-complementary output circuit can also be used. For example, a quasi-complementary output circuit is used inside the LM38886, the LM4766 is used. 5. 3 pairs of SAKCC SAP15N, SAP15P, and schematic are shown in Figure 5. 6.2sk2013 / 2SJ313 pushes 8-to-high power field effect tube or triode (figure) to facilitate enthusiasts to make 100W × 2 purel.
Third, debugging
The above six types of post-casages can calculate the required methylthrics or end-level quiescent currents according to P - A = 2I02RL, thereby debugging the final static current as needed. If the output power is 80W under 8Ω load, the final static current is IO = 2.236, the static current flowing through each tube is IO '= IO / N = 2.236 / 3A = 0 .745a, ie 0.25 Ω / 5W resistor DC pressure drop is V = IO '? R = 745 × 0.25 ≈ 186 (mV).
Although purel Amplifier is soft, sweet, but it has extremely strict requirements for transformers, filter capacitors, power tubes and heat sinks. Listening to a month, the electricity fee is heavy. In this case, the enthusiasts may wish to make the power amplifier as high-biased, such as 20W or less, 20W ~ 100W is the A-class output. At this time, the total static circuit is IO = 1.118a, in fact, the general room environment, 20W, a purellabus output, can meet the listening requirements of most of the enthusiasts.
Since most of the voltage amplifies have been adjusted by the manufacturer, only the final current amplifier is large and related interfaces. Most of the fine-tuning voltage is magnificent to the output of 0mV, adjust the multi-ring potentiometer W2 of the current amplifier, measure the DC voltage across the 0.25Ω / 5W resistor, so that it meets its own requirements, to Fig. 3, Fig. 4 can be directly Measure the voltage of 0.25 Ω / 5W, and the voltage of SAP15N 4, 5 foot or SAP15P1, 2 feet should be measured.
If you test everything is normal, you can simmer for 1 to 2 hours, repeat the parameters, if it is correct, you can play audition. If you want to assemble a purel, you can first adjust the whole machine to high-biased a high-biased amplifier, and the audition is normal, and then increase the static current to the desired value, so that the machine becomes a purel.
The above five current amplifier, the sleeve size is 360mm × 120mm × 50mm, and the finished plate is debugged into high-biased Amplification (20W + 20W), to assemble 80W + 80W pureroa power, only need to be replaced The heat sink is loaded into both sides of the outer dew heat-dissipated equipment (480mm × 430mm × 150mm).
The above lines, the enthusiasts are slightly adjusted (such as changing the transformer power and power supply voltage, power tube logarithm and quiescent current). Such as: making high power amplifiers (250W / 4Ω); making electronic frequency amplifiers; produce high quality headphone amplifiers (push K214 / J77 or K2013 / J313) with this electric voltage plate, use voltage amplifier to some discrete components, low gear Amplifier Movie; Making top 8-channel pure level amplifier (such as 4 voltages, shared power, a pair of Sikin 2SC3858, 2SA1494, etc.).
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