Microphone amplifier based on 4558 circuit. Microphone preamplifier. Wait for the search to complete in all databases. Upon completion, a link will appear to access the found materials
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Most audio lovers are quite categorical and are not ready to compromise when choosing equipment, rightly believing that the perceived sound must be clear, strong and impressive. How to achieve this?
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Amplifier on chip f4558
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Perhaps the main role in resolving this issue will be played by the choice of amplifier.
Function
The amplifier is responsible for the quality and power of sound reproduction. At the same time, when purchasing, you should pay attention to the following designations, which mark the introduction of high technologies in the production of audio equipment:
- Hi-fi. Provides maximum purity and accuracy of sound, freeing it from extraneous noise and distortion.
- Hi-end. The choice of a perfectionist who is willing to pay a lot for the pleasure of discerning the smallest nuances of his favorite musical compositions. Hand-assembled equipment is often included in this category.
Specifications you should pay attention to:
- Entrance and output power. The rated output power is of decisive importance, because edge values are often unreliable.
- Frequency range. Varies from 20 to 20000 Hz.
- Coefficient nonlinear distortion. Everything is simple here - the less the better. The ideal value, according to experts, is 0.1%.
- Signal to noise ratio. Modern technology assumes a value of this indicator over 100 dB, which minimizes extraneous noise when listening.
- Dumping factor. Reflects the output impedance of the amplifier in its relation to the nominal load impedance. In other words, a sufficient damping factor (more than 100) reduces the occurrence of unnecessary vibrations of equipment, etc.
Something to remember: making quality amplifiers- a labor-intensive and high-tech process, respectively, too low a price with decent characteristics should alert you.
Classification
To understand the variety of market offers, it is necessary to distinguish the product according to various criteria. Amplifiers can be classified:
- By power. Preliminary is a kind of intermediate link between the sound source and the final power amplifier. The power amplifier, in turn, is responsible for the strength and volume of the output signal. Together they form a complete amplifier.
Important: the primary conversion and signal processing takes place in the preamplifiers.
- Based on the element base, there are tube, transistor and integrated minds. The latter arose with the goal of combining the advantages and minimizing the disadvantages of the first two, for example, the sound quality of tube amplifiers and the compactness of transistor amplifiers.
- Based on their operating mode, amplifiers are divided into classes. The main classes are A, B, AB. If Class A amplifiers use a lot of power, but produce high-quality sound, Class B amplifiers are exactly the opposite, Class AB seems to be the optimal choice, representing a compromise between signal quality and fairly high efficiency. There are also classes C, D, H and G, which arose with the use of digital technologies. There are also single-cycle and push-pull operating modes of the output stage.
- Depending on the number of channels, amplifiers can be single-, double- and multi-channel. The latter are actively used in home theaters to create volumetric and realistic sound. Most often there are two-channel ones for right and left audio systems, respectively.
Attention: studying the technical components of the purchase is, of course, necessary, but often the decisive factor is simply listening to the equipment according to the principle of whether it sounds or not.
Application
The choice of amplifier is largely justified by the purposes for which it is purchased. We list the main areas of use of audio amplifiers:
- As part of a home audio system. It's obvious that best choice is a tube two-channel single-ended class A, also optimal choice can form a three-channel class AB, where one channel is designated for a subwoofer, with a Hi-fi function.
- For speaker system in the car. The most popular are four-channel AB or D class amplifiers, depending on the financial capabilities of the buyer. Cars also require a crossover function for smooth frequency control, allowing frequencies in the high or low range to be cut as needed.
- In concert equipment. There are justifiably higher demands placed on the quality and capabilities of professional equipment due to the large distribution area sound signals, as well as a high need for intensity and duration of use. Thus, it is recommended to purchase an amplifier of at least class D, capable of operating almost at the limit of its power (70-80% of the declared one), preferably in a housing made of high-tech materials that protects from negative weather conditions and mechanical influences.
- In studio equipment. All of the above is also true for studio equipment. We can add about the largest frequency reproduction range - from 10 Hz to 100 kHz in comparison with that from 20 Hz to 20 kHz in a household amplifier. Also noteworthy is the ability to separately adjust the volume on different channels.
Thus, in order to enjoy clear and high-quality sound for a long time, it is advisable to study in advance all the variety of offers and select the audio equipment option that best suits your needs.
The circuit of a homemade pre-amplifier (preamp) with a tone block is made on the LM4558 chip. An important part of an audio amplifier is the pre-amplifier. It is desirable that it can not only amplify the signal, but also regulate its frequency response.
The figure on the right shows a diagram of a simple stereo pre-amplifier with volume control separately in each channel and a common tone control for both channels for low, mid and high frequencies.
Schematic diagram
The circuit is based on a dual operational amplifier type LM4558. And it is intended primarily for working with simple automobile amplifiers built on microcircuits - integrated bridge UMZCH. Therefore, the “automobile” supply voltage is unipolar 12V.
But this does not limit the scope of application of this scheme only to automotive vehicles.
Rice. 1. Schematic diagram of a homemade pre-amplifier with a tone block based on LM4558.
The supply voltage can be up to 30V. And you can even switch to bipolar power supply. To do this, you need to remove the divider on resistors R1, R2 and C2. And connect pins 3 and 5 of the microcircuit to the common power supply negative. In this case, disconnect pin 4 from the minus power supply and apply a negative supply voltage to it.
Volume adjustment is carried out by variable resistors R7 and R15, as already mentioned, separately in each channel. On the operational amplifiers of the A1 chip, two active tone controls are made, in which both amplification of the audio signal and frequency correction using three-band tone controls occur.
The adjustment circuits are included in the OOS circuits of the operational amplifiers. Volume control for high frequencies - with double variable resistor R8, for mid frequencies - R9, for low frequencies- R10.
Details
The LM4558 microcircuit can be replaced by any IC - two op-amps for general use, or you can make a circuit using two ICs, one op-amp in each.
Microphone preamp, also known as a pre-amplifier or microphone amplifier, is a type of amplifier whose purpose is to amplify weak signal to the linear level (about 0.5-1.5 volts), that is, to an acceptable value at which conventional audio power amplifiers operate.
The input source of acoustic signals for a preamplifier is usually vinyl record pickups, microphones, and pickups of various musical instruments. Below are three circuits of microphone amplifiers on transistors, as well as a variant of a microphone amplifier on the 4558 chip. All of them can be easily assembled with your own hands.
Circuit of a simple microphone preamplifier using one transistor
This microphone preamplifier circuit works with both dynamic and electret microphones.
Dynamic microphones are similar in design to loudspeakers. The acoustic wave affects the membrane and the acoustic coil attached to it. When the membrane oscillates, an electric current is generated in a coil exposed to the magnetic field of a permanent magnet.
The operation of electret microphones is based on the ability of certain types of materials with increased dielectric constant (electrets) to change the surface charge under the influence of acoustic wave. This type Microphones differ from dynamic ones by their high input impedance.
When using an electret microphone, to bias the voltage on the microphone, it is necessary to set the resistance R1
single transistor microphone amplifier
Since this microphone amplifier circuit is for a dynamic microphone, when using an electrodynamic microphone, its resistance should be in the range from 200 to 600 Ohms. In this case, C1 must be set to 10 microfarads. If it is an electrolytic capacitor, then its positive terminal must be connected towards the transistor.
Power is supplied from the crown battery or from a stabilized power source. Although it is better to use a battery to eliminate noise. can be replaced with a domestic one. Electrolytic capacitors for a voltage of 16 volts. To prevent interference, connect the preamplifier to the signal source and to the amplifier input using a shielded wire. If further powerful sound amplification is needed, then you can assemble an amplifier on a microcircuit.
Microphone preamplifier with 2 transistors
The structure of any preamplifier greatly affects its noise characteristics. If we take into account the fact that the high-quality radio components used in the preamplifier circuit still lead to distortion (noise) to one degree or another, then it is obvious that the only way to get a more or less high-quality microphone amplifier is to reduce the number of radio components in the circuit. An example is the following two-stage preliminary circuit.
With this option, the number of decoupling capacitors is minimized, since the transistors are connected in a circuit with a common emitter. There is also a direct connection between the cascades. To stabilize the operating mode of the circuit when the external temperature and supply voltage change, a direct current feedback loop has been added to the circuit.
Preamplifier for electret microphone with three transistors
This is another option. The peculiarity of this microphone amplifier circuit is that power is supplied to the preamplifier circuit through the same conductor (phantom power) through which the input signal travels.
This microphone preamplifier is designed for collaboration with, for example, FEM-3. The supply voltage to the microphone goes through resistance R1. The audio signal from the microphone output is supplied to the VT1 base through capacitor C1. , consisting of resistances R2, R3, creates the necessary bias at the base of VT1 (approximately 0.6 V). The amplified signal from resistor R5, acting as a load, goes to the base of VT2 which is part of the emitter follower on VT2 and VT3.
Near the output connector, two additional elements are installed: load resistor R6, through which power is supplied, and separating capacitor SZ, which separates the output audio signal from the supply voltage.
Pre-microphone amplifier based on 4558 chip
The 4558 operational amplifier is manufactured by ROHM. It is characterized as a low power and low noise amplifier. This microcircuit is used in a microphone amplifier, audio amplifiers, active filters, and voltage-controlled generators. The 4558 chip has internal phase compensation, increased input voltage threshold, high gain and low noise. This op amp also has short circuit protection.
(140.5 Kb, downloads: 2,485)
microphone preamplifier for 4558
This is a good option for building a microphone preamp on a chip. The preamp circuit for the microphone is different high quality reinforcement, simplicity and does not require much strapping. This dynamic microphone amplifier also works well with electret microphones.
Stereo amplifier based on TDA2003 + JRC4558.
We present to your attention a schematic diagram of a complete stereo amplifier built on TDA2003 chips. According to the datasheet, the TDA2003 will produce 6 Watts of power into a 4 Ohm load. The amplifier's power supply is unipolar 12 Volt, so it can be used as a car audio system. If you are interested in the amplifier parameters in more detail, you will find a full description (datasheet) in the archive with the materials of this article. This amplifier also contains a pre-amplifier and three tone controls, which are implemented on the JRC4558 MC. Schematic diagrams shown below:
Power amplifier circuit on TDA2003:
Pre-amp circuit on JRC4558 with three-band tone control:
In the preamplifier, the JRC4558 chip can be replaced, for example, with a TL072.
All elements of the amplifier along with the regulators are placed on one board. The PCB sources are shown below:
Using these images we drew printed circuit board in the Sprint Layout program, below is a view of the LAY6 format amplifier board:
The photo view of LAY6 format is as follows:
Foil fiberglass one-sided, size 71 x 126 mm.
TDA2003 chips are installed on one common radiator, so do not forget about thermal paste and insulating gaskets with insulating bushings.
The convenience of the board lies in the fact that regulators are installed directly on it, therefore the use of wires for external connections is significantly reduced. All variable resistors are paired 2 x 20 kOhm with a linear characteristic, that is, if imported, then with the index “B”, if domestic, with the index “A”.
The appearance of the amplifier board assembly is shown below:
When power is applied to the amplifier, the red LED located next to the input connector lights up. Its circuit contains a current-limiting resistor with a nominal value of 2.2 kOhm.
After soldering the elements, rinse the board thoroughly, for example, with solvent 646, remove excess rosin and make sure there are no “snot” (tin jumpers between the tracks). Check again whether the elements are soldered correctly (chip 4558, polarity of electrolytes, etc.)
The amplifier is assembled without errors and from serviceable parts in additional settings does not need. Happy repetition.
List of amplifier elements with preamp and tone control:
Chips:
● TDA2003 – 2 pcs.
● JRC4558 – 1 pc.
Resistors 1/4W:
● 47R – 2 pcs.
● 2R2 – 2 pcs.
● 220R – 2 pcs.
● 1R/0.5W – 2 pcs.
● 1K – 4 pcs.
● 10K – 2 pcs.
● 2k7 – 4 pcs.
● 100K – 2 pcs.
● 220K – 2 pcs.
● 2k2 – 1 pc.
Capacitors for a voltage of at least 16V:
● 1000mF electrolyte – 2 pcs.
● 470mF electrolyte – 2 pcs.
● 100mF electrolyte – 2 pcs.
● 1mF electrolyte – 6 pcs.
● 10mF electrolyte – 1 pc.
● 0.047mF (473) film – 2 pcs.
● 0.1mF (104) film – 4 pcs.
● 0.1mF (104) ceramics – 1 pc.
● 0.0047mF (472) film – 2 pcs.
● 470pF (471) ceramics – 4 pcs.
Rest:
● Twin variable resistor 20k + 20k - 4 pcs.
● Connector with bolt clamp 2 Pin 5 mm for mounting on a board – 3 pcs.
● Connector with bolt clamp 3 Pin 2.54 mm for mounting on a board – 1 pc.
● LED – LED 5 mm red – 1 pc.
● 8 Pin socket for JRC4558 – 1 pc.
● Aluminum radiator for TDA2003 – 1 pc.
● Double RCA connector – 1 pc.
● Acoustic connection terminal – 1 pc.
You can download the amplifier circuit for TDA2003 & JRC4558, LAY6 format printed circuit board and datasheet_TDA2003 using a direct link from our website, which will appear after clicking on any line of the advertising block below except for the “Paid advertising” line. File size – 0.93 Mb.
