Balancing amplifier for electret microphone. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
Comments on the article
The proposed amplifier for an electret microphone has a practically symmetrical current output to the subsequent amplifier of the mixing console with a symmetrical input, receiving "phantom" power through the signal wires of the connecting cable.
As you know, in professional sound amplification equipment, microphones are connected to balanced (balanced) inputs of amplifiers, which allows using relatively long lines without any noticeable influence of external noise sources on them. For a condenser microphone, the polarizing voltage (usually 48V) is supplied through the input connector from the console's power supply.
Condenser microphones are relatively expensive, and in many cases in amateur practice it is possible to replace them with electret microphones. Such small-sized electret microphones are used, as a rule, in wireless radio microphone devices from Shure, Sennheizer, AKG, or in consumer sound recording equipment. The microphone is a design in which an amplifying stage is also built in to match the microphone with a relatively low-impedance input of the device following it. A thin and flexible cable is removed from the capsule - two cores in the screen.
If it becomes necessary to use an electret microphone, for example, as a pickup for a string or wind instrument, it is not at all necessary to use a radio channel. This microphone can be connected to the balanced microphone input of a mixing console through a simple device, also powered through the input connector.
The matching amplifier (its circuit is shown in the figure) is inseparably connected to the BM1 microphone, which excludes its arbitrary disconnection during operation, causing a voltage surge in the entire amplification channel and a loud click in the speaker system. The microphone is powered through resistor R1 from the emitters of transistors VT1 and VT2. The signal from the microphone is fed to the input of the differential stage (base of transistor VT1) through capacitor C1. From the collectors of transistors VT1 and VT2, the balanced signal is fed to the microphone input of the mixing console or other device.
It also supplies voltage to power the entire device: directly to the collectors of transistors VT1, VT2 and through resistors R5 and R6 to the base circuits of the differential stage.
To stabilize the base bias voltage, a "stabistor" of six silicon diodes connected in series was used. A stable voltage of about 3,6 V is formed on them. The use of a zener diode is undesirable, since the noise level increases markedly.
The device uses a Sennheizer MKE-2 microphone. You can use a similar microphone from another company. Instead of C536A transistors, you can use other low-noise ones with a maximum voltage of UKB ≥50 V, for example, domestic KT3102A or KT3102B with pair selection according to the specified parameter, as well as according to the h21E and UBE parameters. Capacitors C1 and C2 are preferably used specially designed for audio equipment - Black Gate or other well-known companies.
For mounting the amplifier, a breadboard with a grid of holes 2,5x2,5 mm was used. The whole device is housed in a battery case similar to the Krone, which is connected by a conductor to a common wire. The microphone cable is connected to the board: the red wire - to the connection point of R1 and C1, and the blue one - together with the braid to the common wire. To the points on the board, to which the collectors of both transistors are connected, and to the common wire, a balanced cable is connected, on the other end of which an XLR connector plug is soldered. You can check the electrical modes of the device by connecting it directly to the microphone input of the mixing console (phantom power must be on) or or to a source of stabilized voltage +45...48 V by connecting pins 2 and 3 of connector X1 to the positive output of the power source through resistors with a resistance of 33 kOhm, and pin 1 to the negative one. When measuring the current in the power circuit break, you need to make sure that it does not exceed 2 mA. Then you need to measure the voltage across the resistor R2; it should be about 3 V. Next, the device must be tested in action.
Author: M. Sapozhnikov, Ganei Aviv, Israel
See other articles Section Transistor power amplifiers.
Read and write useful comments on this article.
<< Back
Latest news of science and technology, new electronics:
Machine for thinning flowers in gardens
02.05.2024
In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers.
... >>
Advanced Infrared Microscope
02.05.2024
Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>
Air trap for insects
01.05.2024
Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>
| Random news from the Archive The benefits and harms of video games
12.08.2017
Researchers from the University of Montreal invited XNUMX volunteers, who were roughly equal in size to men and women, to walk through a virtual maze. There were several paths in the labyrinth where it was necessary to collect certain items, and this task could be completed faster if you memorized the routes that you had already walked - that is, you should pay attention to various surrounding signs, such as stone, wood, etc. .
With such an orientation to the terrain, the hippocampus is triggered in our brain - a special area in the brain that serves as one of the main memory centers and at the same time plays the role of a cartographer, that is, it builds maps of the surrounding landscape.
But in the labyrinth it was possible to do otherwise - just remember the sequence of turns to the right and left. In this case, another area of the brain comes into play, partly duplicating the functions of the hippocampus - the caudate nucleus, which is part of the striatum.
The caudate nucleus works as an autopilot, allowing us to perform certain automatic actions, and at the same time it is included in the reinforcement system - this is the name of a large complex of nerve centers that controls our motivation, our desires and feelings of pleasure.
You can also follow the route with the help of the caudate nucleus, however, here it will not be so much a map of the area as remembering the actions that need to be performed for a reward: remembering how many times and where you turned before, you can get to the next desired item in the maze and get a portion pleasant sensations.
The maze search made it possible to separate those who build maps with the help of the hippocampus and those who follow the route with the help of the caudate nucleus, an autopilot that seeks pleasure. Then some of the participants in the experiment were put into playing shooter games, while others took up 3-D platform games in the Super Mario Bros series; both those and others had to "play enough" for about 90 hours.
And it turned out that games have different effects on the brain. If a person who walked along the route, obeying the reinforcement system, played a shooter game, then as a result, the amount of gray matter in his hippocampus decreased. The authors of the work explain this by the fact that such games, in principle, tend to encourage the reinforcement system, so that in "chronic players" the hippocampus can shrink quite strongly, as if it is unnecessary. We say "as if" because the hippocampus, whatever one may say, is still needed outside the video shooter, and the consequences of a lack of gray matter in it can be quite serious - it is known that a decrease in the hippocampus accompanies depression, schizophrenia, Alzheimer's syndrome, etc. d.
On the other hand, for those players who navigated the terrain, combining in their minds different elements of the landscape - that is, for those who initially were more involved in the navigational skills of the hippocampus - the gray matter in it, on the contrary, became larger; that is, even in a shooter, they were guided by a neutral map, and not by anticipation of pleasure.
Finally, the platformer about the Mario brothers contributed to the strengthening of the hippocampus in both categories of players - obviously, the very structure of such games forces you to build maps in your mind.
|
Other interesting news:
▪ Purification of drinking water from drugs
▪ Hidden identification with invisible QR codes
▪ Texas Instruments DRV5055 and DRV5056 Hall Sensors
▪ Artificial organic neurons
▪ Restoration of tooth enamel
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ section of the site Radio - for beginners. Article selection
▪ article What are gossips to consider working, isn’t it better to turn around for yourself, godfather? Popular expression
▪ article Why is alternating current rather than direct current used for the transmission and distribution of electrical energy? Detailed answer
▪ Woutley article. Legends, cultivation, methods of application
▪ article Generator of a harmonic signal with a soft limiter. Encyclopedia of radio electronics and electrical engineering
▪ article Cane and flowers. Focus Secret
Leave your comment on this article:
All languages of this page
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua
2000-2024
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese