Speaking of the small power of the ear, I have to mention the 20th century emperor Ne5532, I have appeared in countless excellent pre-magnification, the tuning circuit, the center is warm and delicate, the gallbladder is full, the price is very high! Until today we can easily find it in some medium and low-end audio products. Due to its small size, the circuit is simple, it is the first choice for practical and low-input. Because NE5532 has been very familiar with the circuit from the past, everyone is very familiar with it, and has a variety of ways to play. The character introduced here is simple, small power, and focusing on the process of making. I. Principle Analysis NE5532 is a typical bipolar input operational amplifier, there are many versions of small power circuits composed of single NE5532, I have made a modification of the five-flowers of circuit maps by constantly contrast and thinking, and finally identify the schematic ( figure 1). The magnification is controlled by R3 (R4) and R5 (R6). In theory, if R3 (R4) is 1kΩ, R5 (R6) is 100KΩ, the magnification is 100 times, but for the ear, This will cause self-excitement, and then, even if it can really reach 100 times, the effect is impossible, so this circuit is used in the pre-stage, it is best not to adjust 100 times. Of course, for the ear, it can make the negative feedback amount, the sound quality is soft, and it is clear and more transparent, but the magnification is not too small, otherwise it will affect the sound quality. You can repeated debugging, achieving the effect of your own satisfaction. The author is set to 1kΩ, R5 (R6) is set to 20 kΩ, which is 2 times. C5 (C6) is a local pathway of the input loop. It should be increased when used for an ear-on circuit, and the value in the schematic is 22 Uf, but it is used for this ear should increase to 100 uf. It is worth mentioning here that power problems, if you are using the regulated power supply, pay attention to the filtering of the regulated power supply to give enough, because the circuit itself is very simple, then choose the selection of components, it is recommended. Try to choose a moiety to choose a moiety when selecting. Second, PCB Drawing the author using Protel 99 SE to wiring design, everyone see this PCB map (Figure 2) is the third edition I painted, is also my most satisfactory version, the first few editions have a flying line, and This version is not, there are many versions of the online version of the flight, which can't be tolerated for the picky-topened hand. Due to small area, it is necessary to try to get a little grounding, input, and output, according to the actual situation. Still all components, neatly qualify, and look very harmonious. Third, the selection of materials for materials, I believe that all the friends have different channels, because the author is better procurement in the main city of Chongqing, this time, in addition to buying new components, I also bought some old tonic, used Not enough 10 yuan. 1. Polar capacitor: Select 10 UF / 50V, C5 (C6) selected from 1 (C1 (C6), selected from 10 UF / 50V, C9 (C10), can be selected 47 UF ~ 220 UF. I use 47 UF, I have no effect, and everyone can change it. 2. No polar capacitance: It is best to match when purchasing, the author chooses second-hand German WiMA and Swedish Evox white square MMK film capacitance. C3 (C4) is 200 pf (or 220pF), C7 (C8) is 0.1 Uf. 3. NE5532: Select NE5532 produced by Signetics, commonly known as large S5532, is the best listening to many production 5532 manufacturers (already discontinued for many years), is the first year's four big king. The author only found second-hand, if you can't find it, you can choose Philip, of course, the ceramics is also good. 4. All resistors will use the five-ring metal film resistance, and the domestic big red robe collected is also used, and it is no longer detailed. 5. The copper-copper used by the circuit is the angle of the 捡 (I heard that others used to use the TV board, I believe it will not be very poor, the thickness is also enough). Fourth, after the preparation is fully prepared, the production of PCBs, there are many ways to hand tool, such as dedicated scribes (with conditional schools, high cost, but the quality of the board is also the highest). Light plate and thermal transfer. Since the author's hand is limited, the thermal transfer method is used. Suggested here: After the PCB is corroded and dried, it is best to punch, then use sandpaper to brighter, apply the solution of rosin to alcohol, which can be soldered and oxidized. After the PCB is done, it can be welded. The principle is the first soldering resistance, reloading the capacitor, and the three down five are soldered. It is worth reminding: My PCB input, the output is the plugin for choosing, but in practice, because of the case of the shell, I didn't sell the plug-in directly on the PCB, some friends who have a material and hands-on can do it yourself. Be a housing. After the fineness of the five beautification is finished, the first goes to debug, and after debugging the previous method, it will be packaged. Flip box, finally found a box, the metal box when I bought a U disk, there is a transparent window to watch the window, and take a good position. Many friends like to listen to pure tones, and have not used the volume potentiometer, so the author does not draw on the board. If some friends want to add a volume potentiometer like the author, the potentiometer is 50kΩ, the next method is simple. In terms of power supply, friends who like to use a regulated power supply should be adjusted to the double 15V left and right effects. The author used two 9V dry batteries, mainly for convenience. Cover the box, this little ear can go to the horse, its effect is much better than the previous production, and the sound area is wider, the sound quality is more soft. This simple circuit, interested friends may wish to try.
Our other product:
