Operational amplifier is a widely used linear integrated circuit. Moreover, there are many kinds. In application, it can not only amplify weak signals, but also act as an inverter and voltage follower, and can add and subtract electrical signals, so it is called operational amplifier. It is not only widely used in other places, but also in acoustics. For example, preamplifiers and buffers, except for some discrete components and electron tubes, most headphone amplifiers use integrated operational amplifiers. Sometimes it is used in voltage stabilizing circuit to make high-precision voltage stabilizing filter circuit. Various operational amplifiers have different timbre characteristics because of their different internal structures and distortion components. Originally, what we are pursuing is high fidelity, and the operational amplifier should be the best with the lowest distortion, which can truly restore music and has no personality. However, due to the need to cooperate with other audio components, such as digital sound source, post-amplifier tube, etc., if it is dry and cold, it can be matched with an operational amplifier with a delicate and warm tone, and if it is too soft, it can be matched with an operational amplifier with a bright tone of Leng Yan, so as to achieve the best effect of the whole machine's cooperation and complement each other. Therefore, it is not that the more expensive the operational amplifier, the better the effect. Matching is very important, and the best hearing is the best way to achieve the goal. If it is used in low-voltage analog filter circuit, it is necessary to choose the operational amplifier with good low-voltage performance. There are no fewer than 500 kinds of operational amplifiers in the market, more than 300 kinds with GBW bandwidth above 5M, up to 300MHZ, and hundreds of kinds with conversion rate above 5V/us, up to 3000V/us. The above types of audio enthusiasts have been heated up. In fact, there are many excellent products that are not well known to everyone to choose from. You don't have to be limited to the above types. The package of operational amplifier model can also be divided into gold package, ceramic package and plastic package. Generally speaking, the quality of gold seal and ceramic seal is better, but the quality of plastic seal is slightly worse. Driven by interests, everything is fake, and distribution is no exception. There are many fakes in the market. If you want to pick up cheap and good goods, you must have a vision. If you are not very good at it, you should pay attention when buying it. They would rather spend a few extra cents to buy from reputable businesses.

Low level operational amplifier JRC4558. This kind of operational amplifier is mostly used in low-end machines. Now it is considered to be super bad, because its sound is too bright and has a strong sense of burr, so it is the worst one compared with other sound response operational amplifiers. However, it is still widely used in China for the time being, and many amplifiers whose cost is in 400 yuan or 500 yuan are still selected, because considering the cost and actual effect, it is not necessary to choose operational amplifiers with quality above 5532. For some computer active speakers, its coping ability is more than enough.

The emperor in the play. If someone hasn't heard its name, it's not a sound lover. NE5532, once known as the king of operational amplifiers, is also known as the four famous operational amplifiers with LM833, LF353 and CA3240, but now only 5532 is used the most. Now 5532 is mainly produced in Taiwan Province Province, the United States and Philips, and also in Japan. The best products are American products with the big S logo. Authentic products should be sold above 8 yuan. Since SIGNE was acquired by Philips, all the 5532 trademarks produced are trademarks of Philips, and the quality is equivalent to the original products, only 4-5 yuan. The quality produced in Taiwan Province Province is slightly worse, and the price is also the most convenient. You can buy it for two or three yuan. The package of NE5532, like 4558, is a DIP8 pin dual operational amplifier. Inside 5532 is JFET (junction field effect transistor structure). The overall sound features are warm and delicate, with strong driving force, but the high notes are slightly rough and the low notes are fat. In the past, many people thought it was a little "bile flavor", but now it is much more than it, and it is relatively less prominent. 5532 has a wide voltage adaptation range, and can work normally from plus or minus 3V to plus or minus 20V. Although it is an old operational amplifier, it is still considered to be the most cost-effective operational amplifier for audio. It is a civil operational amplifier, which is adopted by many low-end power amplifiers. But there are too many fake NE5532 or industrial products that are not used for audio. Because the pin function of 5532 is the same as that of 4558, some unscrupulous merchants erase the letters of 4558 and print 5532 as 5532. Generally, the appearance is rough, the printing is easy to erase, and people with little experience can distinguish it. It is said that 8mA warm current is the authentic audio. NE5532 has two brothers, NE5534 and NE5535. 5534 is a single operational amplifier. Because it separates a single operational amplifier and there is no interaction between the two operational amplifiers, the timbre is not only soft, warm and delicate, but also has a good musical taste. Its voltage adaptation range is also very wide, and the voltage as low as plus or minus 5V can keep good working condition. Because the famous BGW- 150 power amplifier in the United States used 5534 as the voltage excitation, the positive power supply voltage was deliberately higher than 0.7V, forcing its output tube to work in a more perfect class A state, further improving the sound quality, so it is generally believed that the sound quality of the positive power supply above 0.7V will be better ... The pin function of 5534 is shown in the figure, and the price is equivalent to that of 5532. NE5535 is an upgraded product of 5532, which is characterized by simpler internal circuit and completely complementary output stages. The conversion rate is higher than 5532. However, there is a disadvantage that the noise is large, the frequency band is not wide enough, and the bottom voltage performance is not good enough, so the effect is not as good as that of 5532 when it is used for analog filtering. But when the working voltage is greater than or equal to 15V, the music taste will be better than that of 5532, so its price is two or three yuan more expensive than that of 5532, and the pin function is the same as that of 5532.

AD827 dual op amp. This is a relatively new product of the advertising company. It was originally designed for video circuits, so its gain bandwidth reaches 50MHZ and SR reaches 300V/us. Like EL2244, it is the top product of voltage feedback dual operational amplifier on the market at present, and the general operational amplifier is far behind. Its high-frequency operation is transparent, its low-frequency bounce feeling is outstanding, its performance index and actual listening feeling are better than many other similar products, and its sound quality is also described by some people as impeccable. And it still has excellent performance under the power supply of plus or minus 5V. But its price is also slightly more expensive, more than 30 yuan. Foot position function is the same as 5532.

Dual op amp OP249. Operational amplifier is a product of American PMI company. The manufacturer claims to replace OP2 15, LT 1057 and other operational amplifiers. LT 1057 is a dynamic Leng Yan with high resolution and beautiful timbre, which is suitable for matching with Toshiba's warm-colored famous pipes. On the other hand, OP249 is different. Its input stage adopts JFET, and its main features are neutral, impersonal, balanced, natural and accurate, which embodies the true meaning of HIFI. Plastic packaging only needs 15 yuan, and ceramic packaging costs more than 30 yuan, which is very cost-effective. But friends who have a preference for timbre may not like it very much.

Dual operational amplifiers OP275 and OP285: also products of PMI company, the internal circuit adopts a mixed structure of two stages and JFET. Its timbre is very individual, with low noise, well-defined sound, high resolution and soft voice. The intermediate frequency has the characteristics of softness and courage, and the sound is close. Moderate price and stable performance. Suitable for rubbing CD, decoder or amplifier with thin and rough sound. Their package forms and pin functions are the same as those of 5532. OP275 current market price 10 yuan, OP285 15 yuan.

Top op amp OPA627. The OPA627 of BB Company is by far the most advanced operational amplifier, and it also adopts the input mode of field effect transistor. Its timbre is warm and charming, but its price is simply frightening. Whether the performance of such an expensive operational amplifier can reach this price is also a matter of opinion, but all enthusiasts who have heard of OPA627 agree that the AD827, LT 1057 can't be compared with it at all.

OPA604 and OPA2604 release bile flavor. These two operational amplifiers are products of Burr Brown, OPA604 is a single operational amplifier, and OPA2604 is a dual operational amplifier. They are all special operational amplifiers specially designed for audio. They are mellow and mellow in tone, warm and neutral, and have a strong bile taste. They are regarded as the operational amplifiers with the most tone of electronic tubes. At that time, the price was not low, but it was still chosen by many audio enthusiasts as the object of motorcycle upgrading. At present, the prices of these two operational amplifiers are reasonable. Opa604 from 25 yuan, opa 2604 40 yuan. It is a good choice for enthusiasts to ride motorcycles.

If you want to buy it, it is usually Taobao. If the quantity is large, you can directly find an agent or contact the manufacturer.