Overview of Commonly Used Op Amps

Low-end op amp JRC4558. This op amp is the most used in low-end machines. Now it is considered super bad because its sound is too bright and has strong burrs, so it is the worst op amp compared to other audio op amps. However, it is still widely used in China for the time being. Many power amplifiers of four or five hundred yuan still choose to use it, because considering the cost and the actual effect, there is no need to choose an op amp with a quality higher than 5532. For some computer active speakers, its coping ability is more than enough. The king of op amps 5532.

If anyone has not heard of its name, then he is not yet an audio enthusiast. The NE5532, which was known as the king of op amps in the past, is one of the four famous op amps of the old brand together with LM833, LF353, and CA3240, but now only 5532 is used the most. 5532 is now mainly produced in Taiwan, the United States and PHILIPS, and also in Japan. 5532 was originally a product of SIGNE, USA, so the best quality is the American product with the big S logo. The authentic one on the market costs more than 8 yuan. Since SIGNE was acquired by PHILIPS, the 5532 produced is all PHILIPS, and the quality is equivalent to the original product, and it only costs 4-5 yuan. The quality of Taiwan-made products is slightly worse, and the price is the cheapest, and you can buy it for two or three yuan. The package of NE5532 is the same as 4558, both are DIP8-pin dual op amps (see the functional pins in the figure). The sound characteristics are generally warm and delicate, with strong driving force, but the treble is slightly rough and the bass is fat. In the past, many people thought it had a little "tube flavor", but now there are many more tube flavors than it, so it is relatively not so prominent. The voltage adaptation range of 5532 is very wide, and it can work normally from positive and negative 3V to positive and negative 20V. Although it is a relatively old op amp model, it is still considered to be the most cost-effective audio op amp. It is a kind of civilian op amp, adopted by many mid-range power amplifiers. However, there are too many counterfeit NE5532 or industrial products for non-audio use. Since the pin function of 5532 is the same as that of 4558, some unscrupulous merchants also erase the letters of 4558 and print 5532 on it to pretend to be 5532. Generally, the appearance is rough and the printing is easy to erase. People with a little experience can also identify it. It is said that only when the current is warm at 8mA is the authentic audio 5532.

NE5532 has two brothers, NE5534 and NE5535. 5534 is a single op amp. Since it separates the single op amp and there is no mutual influence between the dual op amps, the tone is not only soft, warm and delicate, but also has a better musical taste. Its voltage adaptability range is also very wide, and it can maintain a good working condition as low as positive or negative 5V. Since the famous American BGW-150 amplifier used 5534 as voltage excitation, it deliberately made the positive power supply voltage 0.7V higher, forcing its output tube to work in a more perfect Class A state, which further improved the sound quality, it is generally believed that the sound quality will be better if the positive power supply is 0.7V higher. The pin function of 5534 is shown in (Figure), and the price is equivalent to 5532. NE5535 is an upgraded product of 5532, which is characterized by a simpler internal circuit and a fully complementary structure in the output stage. The conversion rate is higher than that of 5532. However, there is a disadvantage that the noise is large, the frequency band is not wide enough, and the performance is not good enough when working at low voltage, so the effect is not as ideal as 5532 when used for analog filtering. But when the working voltage is greater than or equal to 15V, it is used as a linear amplifier circuit, and the music taste will be better than 5532, so its price is also two or three yuan more expensive than 5532, and its pin function is the same as 5532.

Dual op amp AD827. This is a new product of AD company. It was originally designed for video circuits, so its gain bandwidth reaches 50MHZ and SR reaches 300V/us. It is the top product of voltage feedback dual op amp on the market, just like EL2244. It is hard for ordinary op amps to match it. Its high frequency operation is clear, and its low frequency bounce is superior. Its performance index and actual listening experience are better than many other similar products. Some people describe its sound quality as impeccable. And it still has excellent performance under the power supply of positive and negative 5V. But its price is also slightly expensive, more than 30 yuan. The pin function is the same as 5532.

Dual op amp OP249. This op amp is a product of PMI company in the United States. The manufacturer claims that it is used to replace op amps such as OP215 and LT1057. LT1057 is a kind of op amp with large dynamic, high resolution, cool and beautiful sound, which is very suitable for matching with Toshiba's warm color tube. OP249 is different from it. Its input stage uses JFET. Its main feature is neutrality, no personality, balanced, natural and accurate sound, so it embodies the true meaning of HIFI. The plastic package is only 15 yuan, and the ceramic package is more than 30 yuan, which has a high cost performance. However, friends who have a preference for tone may not like it.

Dual op amps OP275 and OP285: They are also products of PMI. The internal circuit adopts a hybrid structure of dual-stage and JFET. Its tone is very individual, low noise, clear sound contour, high resolution, smooth sound, the intermediate frequency has the soft and moist characteristics of tube amplifier, and the human voice is close. The price is moderate and the performance is stable. It is suitable for polishing CDs, decoders or amplifiers with thin and rough sounds. Their packaging form and pin functions are also the same as 5532. The current market price of OP275 is 10 yuan and OP285 is 15 yuan.

Top op amp OPA627. BB's OPA627 is the most advanced op amp so far. It also uses field effect tube input, and the sound is warm and charming, but its price is simply scary, reaching 150 yuan, so it is generally not used in machines that are not top-level. Whether the performance can reach this price is also a matter of opinion, but audiophiles who have heard of OPA627 all agree that AD827, LT1057, etc. cannot compare with it.

Tube-flavored op amps OPA604 and OPA2604. Both op amps are products of Burr Brown, OPA604 is a single op amp, and OPA2604 is a dual op amp. They are both special op amps designed for audio, with mellow and round sound, neutral and warm, and strong tube flavor. They are known as the op amps with the most tube-like sound. The price was not low at that time, but it was still chosen by many audiophiles as the object of upgrading the machine. The prices of these two op amps are now relatively reasonable, OPA604 is 25 yuan, and OPA2604 is more than 40 yuan, which are good choices for audiophiles to use to debug their machines.