5 Bands Graphic Equalizer
Based on the famous BA3822LS equalizer chip.
Introduction:
Many times when we hear a song we feel the need to change the parameters of the original EQ, adjusting this to our liking. While a song is recorded, mixed, equalized and mastered by experts, it is impossible to make a mix to suit the taste of each, which is different according to your personal settings and cultural environment that surrounds the listener.
This is the moment we need an equalizer. Normally found three band EQ (Low, medium and high), but sometimes we fail to balance sound we want.
To reduce this problem we have an equalizer that divide the audible aspect in more parts. In this paper we present a 5-band equalizer gives us the ability to "color" a little better our favorite songs.
What is an EQUALIZER?
The equalizer is a sound processor to split the original audio signal and modify the volume level independently. Each signal portion is called Band. Each band is responsible for increasing the volume of a certain frequency range. The human hearing range is from 20Hz , up to 20kHz . This EQ has 5 band-pass filters consist of capacitors and potentiometers that filter the desired frequency band.
Band peaks are affected by this EQ: Bass ( 100Hz ), middle income ( 330Hz ), middle ( 1kHz ), upper middle ( 3.3kHz ) and high ( 10kHz ).
The materials of the 5-band stereo equalizer are very cheap and easily available. Check before starting the assembly of the circuit you have on hand all the necessary components for assembly. So the work is done faster and nicer, and there's nothing more boring than having to be traveling to get what you missed. For this we must carefully review the list of materials found in the PDF file and compare with the mask components, which we will use as a guide for the correct assembly of the circuit. It should be very careful when placing each component in place. Electrolytic capacitors, regulator and integrated circuits must respect the established polarity.
The integrated circuit BA3822LS stereo graphic equalizer is a five-point frequency control. BA3822LS has two channels within five center frequencies of each channel can be independently set using external capacitors.
This IC has a wide feeding range, ranging from 3.5 volts to 14 volts DC. The integrated package is 24-pin SOIC or SZIP. This makes it an ideal choice for home stereo systems, for their videoke or for use as an equalizer in the car.
Inside BA3822LS has 10 operational amplifiers. This facilitates the assembly of the circuit, reducing space and with a very affordable price.
Assembly:
We put all the resistors in place. The wrong placement of a part could cost us time and money. Then proceed to solder the resistors.
Next is to insert and solder all the capacitors, starting with ceramic type then Mylar. Since this capacitors doesn't have POLARITY, you can insert it in any direction..Just double check the value of the capacitors.
The 8 pins IC socket has a NOTCH on the other end to indicate the proper placement of the IC later..Follow the placement on the parts placement guide.
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| Observed the placement of IC SOCKET! |
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| Double check the VALUE of capacitors based on PARTS PLACEMENT GUIDE printed on the PCB. |
Electrolytic capacitors are POLARIZED devices . For this reason it is very important to check the PARTS PLACEMENT guide for the proper POLARITY before placement.
To identify the polarity of a capacitor, note the white stripe with a minus sign, this is the negative lead of the capacitor. Also their polarity may be identified as its positive terminal is longer than the negative terminal.
On the PARTS PLACEMENT GUIDE, a circle with a small DOT that indicates the negative lead of the Electrolytic capacitors.
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| Proper placement of Electrolytic capacitors. |
The circuit has a built-in rectifier diode, filter and regulator, so you can power it with AC or DC source..
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| Bridge rectified diode. |
The regulator LM7809 delivers a voltage of 9 volts and a current of up to 1 amp. Our EQ regulator can be supplied with 12 - 24 VDC without any problems. Identifying a regulator should be noted that the letters LM corresponding to the mark of the component. In this case belongs to the American company National Semiconductor, which manufactures electronic components. The next two numbers ( 78 ) mean that the regulator is positive and the last two numbers ( 09 ), determine the output voltage of the regulator. In this case, 9V delivery. Remember that this controller can only be supplied with a voltage below 32 volts DC, if for some reason is supplied with a higher voltage, the regulator will burn.
A regulator needs a DC voltage of at least 3 volts above the voltage delivery. For this reason we recommend feeding the circuit with at least 12 volts AC. If the transformer is too low, we will not get at least 3 volts above, necessary for the regulator to do its job and give us 9 volts.
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| LM7809, 9 volts regulator. |
In the picture you can see the filter capacitor after bridge rectifier diode. This capacitor can be 1000 uF to 2200 uF at least 25VDC. Its function is to load and maintain voltage so that it does not fall at the end and beginning of each half cycle, thus converting alternating current (AC) into direct current (DC). can also observe three-pin connectors (GP). These connectors are very useful when removing the equalizer for maintenance or repair. The connector power input we have removed the center pin.
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| Power supply section. |
As BA3822LS has no gain, ie outputs a signal of the same volume that you get, We make this operational to give a bit of gain to the signal. Resistors 2.2K going to the inverting inputs 2 and 6 respectively and 100K resistors ranging between inputs and outputs of the integrated, are responsible for the gain. 100K 2.2K Dividing, we get a gain of 45.
If you need more gain, only 2.2K resistors change by about 1K. But if you just want to decrease the gain, can be altered 5.6k resistors, up to 10K.
The TL072 can replace the JRC4558 , the TL082 or NE5532
Insert and solder the dual 50K potentiometers for the equalizer controls and the dual 20K potentiometer for the volume control.
Before testing the circuit, inspect the PCB against the light, that has no short between tracks. Clean the PCB with a toothbrush and lacquer thinner, to remove grease and possible solder particles remain attached after soldering.
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| Finished equalizer board. |
Download the schematic and PCB layout here: Schematic and PCB
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