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Audio sociable is a device that uses to blend, and change the degree, tone of the sound, and kineticss of audio signals. Audio sociables are besides called commixture consoles and sound boards. Mixer is a device that can blend signals no affair it is linear or digital ; depend on the type of sociable. It sums 2 amplified sound signals, and blend the sound. By summing the modified signals, we can bring forth the combined end product signals that can drive the talker. It can besides command volume and other effects.

Audio sociable are used in many applications, including entering studios, public reference systems, sound support systems, broadcast medium, telecasting, and movie post-production. Simple application is to enable the signals that originated from two separate mikes to be heard through one set of talkers at the same time.

Audio sociable is made up of 2 input sound, crossfader, 3 set in writing equaliser, inverting amplifier, electromotive force follower, electromotive force degree index and talker.

Figure 1: Audio sociable block diagram

Figure 2: Audio sociable

Figure 3: Audio sociable simulation

Audio sociable is builds by utilizing 741 op As.

Operational amplifiers ( op As ) can magnify and run on parallel signals. Applications of op-amp are summing amplifier, electromotive force follower, comparator and active filter.

Op A consists of inverting terminal, non inverting terminus, end product terminus, positive and negative District of Columbia supply terminus, and particular terminuss for tuning.

An ideal op A has high, low and high

Figure 4: Op amp 741 and pin assignments

, where is unfastened cringle electromotive force addition.

For ideal op A, Ao=? , Rin=? , Rout=0.

Figure 5: Ideal op amp Figure 6: Practical op A

Theory:

Crossfader:

A fader is a device that used for attenuation, like a boss or a button that can skid along a path or slot. A fader can be linear which can straight command the electric resistance or opposition to the beginning ; or digital, which can command a digital signal processor ( DSP ) numerically. Digital fader is like a practical fader, as they can be viewed on the screen of a digital audio workstation.

Crossfader is a really of import constituent in audio sociable, as it can blend signals from two different channels. It allows to play 2 channels at the same time and melting between single channels. It acts like summing amplifier.

Crossfader is of import to the Audio Mixer Design due to its features and ability to engage two sound through attenuation.

Figure 7: crossfader

3-band in writing equaliser:

Equalizer is designed to change frequence balance of an audio signal. In in-between and high terminal stereo sound systems, we can normally see in writing equalisers. In telephone system, in writing equaliser is used to repair the cut down degree of high frequences. They can be usage in personal computing machines for all right tuning of sound. Graphic equalisers are used as a standard pattern in unrecorded sound reinforcement systems, professional recording studios, and some high fidelity systems, because it can counterbalance for the room frequence response and room acoustics. Although there are many designs of in writing equalisers, they operate in the same manner.

Graphic equaliser can be in writing or parametric.

Graphic equalisers can be usage to increase the fixed set sound frequences, while the parametric equalisers allows any set to hike up its fc and bandwidth.

Figure 8: Equalizer

The quality factor is use to mensurate the effects of equaliser set on frequences. To command a smaller frequence envelope usage high Q and will give a narrow form to the response.

3-band in writing equaliser is a circuit consists of several set base on balls filter.

Filter is a circuit that can choose a specific scope of frequences to go through through it while barricading other frequences. We can utilize filter to cut down unwanted noise.

The 4 basic types of filters are low base on balls filter, high base on balls filter, set base on balls filter and set reject filter

There are 2 types of filters which are inactive filter and active filter. Passive filter is concepts utilizing inactive elements like R, C and L. While the active filter can be construct utilizing op-amps, R, C. It can manage low frequence signals and provides Av on the same clip. But it is non dependable in high frequences due to the BW of amplifier and slew-rate.

.

Passive RC low base on balls filter Passive RC high base on balls filter

Active RC low base on balls filter Active RC high base on balls filter

Active low base on balls with Active high base on balls with

Band base on balls filter is concepts by uniting the low base on balls and high base on balls filter. The upper frequence is set utilizing low base on balls filter while the lower frequence can be set utilizing the high base on balls filter.

Cascading a inactive RC low base on balls filter and a inactive RC high base on balls filter will bring forth a inactive RC set base on balls filter.

There are 2 ways to build an active RC set base on balls filter. The 1st method is utilizing a inactive RC set base on balls filter with an op-amp. The 2nd method is to cascade a inactive RC low base on balls with op A and a inactive RC high base on balls with op A. 2 op-amps better than one op A because of the seperation of the low base on balls filter and high base on balls filter phase.

Active individual phase set base on balls filter Active cascaded set base on balls filter

Figure 9: 3-band in writing equaliser

Inverting summer amplifier:

Inverting summer amplifier is use to magnify the amount of 2 input signals. It can link more than one linear signal to the input, and the summing amplifier will so magnify each single signal and add them all together. With the handiness of such a system, multiple inputs may be added to a system. So, it is non restricted to a bound of two or three inputs.

In audio sociable, summing amplifier allows us to enter vocals to many paths. By utilizing summing amplifier, we can magnify the sound and do it louder.

Figure 10: Inverting summer

Voltage Follower/Buffer:

Voltage follower follows the electromotive force that is sent in. It have the ability to buffer a high electric resistance signal can do this a utile small circuit. You can utilize this to give more power to a long detector overseas telegram tally, lower electric resistance, and protect circuitry from being overloaded.

Voltage follower is utile for circuit isolation applications ( circuit act like buffer ) .

Small power is drawn from beginning, and this will avoid loading effects. ( Loading effects means big burden electric resistance pull little burden current, so lading of beginning is little )

Voltage follower is used to reassign a electromotive force from a high end product electric resistance degree to a low input electric resistance degree. It can forestall the 2nd circuit from lading the 1st circuit unsuitably and interfering with its coveted operation. Buffer has unity addition amplifier ( =1 ) .

In design of audio sociable, there will be lading consequence created by the talker as the talker draws much current and power from the circuit. So by adding buffer in the circuit, we can cut down power ingestion in the beginning, deformation from overloading, XT and other electromagnetic intervention.

Figure 11: Voltage Follower

Voltage Level Indicator:

Voltage degree index is a simple application utilizing comparators.

Function of the comparator is to find which signal is bigger. We can cognize whether there is any signal that exceeds Vth by utilizing comparator.

Many comparators will portion same input and each of them is supplied with different mention or triping electromotive force.

LEDs will turn on by the end products of comparators depend on the input signal electromotive force.

LEDs will be turned on in sequence when the input signal electromotive force additions.

Audio signal is like the input to the comparator, while LEDs is like a volume index. It addition and decreases when the signals of sound are different.

Figure 12: Voltage degree index

Apparatus:

Equipment:

Power supply: 1 unit

Function generator: 1 unit

Oscilloscope: 1 unit

Digital multimeter: 1 unit

Components:

Op amp 741: 13 units

Resistor 240? : 2 units

Resistor 510? : 1 unit

Resistor 1k? : 10 units

Resistor 2.7k? : 2 units

Resistor 3k? : 2 units

Resistor 8k? : 2 units

Resistor 10k? : 6 units

Potentiometer 10k? : 4 units

Potentiometer 50k? : 1 unit

Capacitor 0.1uF: 2 units

Capacitor 10nF: 2 units

Capacitor 4.7nF: 2 units

LED 5mm: 4 units

Audio doodly-squat: 2 units

Speaker: 1 unit

Circuit building:

Audio Mixer

Crossfader circuit was constructed. The circuit was tested with map generator and CRO to do certain it can work decently.

3-band in writing equaliser circuit was constructed. It was tested with map generator and CRO to do certain it works decently.

Inverting summer circuit was constructed with 3 inputs, and potentiometer. It was tested with map generator and CRO to do certain it works decently.

Voltage follower was constructed. It was tested with map generator and CRO to do certain it works decently.

Voltage flat index circuit was constructed. It was tested with map generator to do certain it works decently.

All the circuits were constructed together as in the figure of audio sociable. Make certain the end product of the 3-band equaliser each is connected to one of the input of the inverting summer. The audio 1 and audio 2 can be signal from a map generator.

Make sure the talker ‘s mutual opposition is connected right.

Whole circuit was tested with input signal from map generator, and from low frequence easy to high frequence. Speaker should bombinate from low tone to high tone.

When all circuits work decently, it was tested with an audio signal ( to audio 1 ) from computing machine by linking audio doodly-squat to PC end product doodly-squat. Circuit was verified by talk before trying connexion to Personal computer.

If audio 1 plants decently, audio 2 was so tested

Audio 1 and audio 2 were tested with two different audio signals from the Personal computer

Crossfader

Circuit with was constructed.

Function generator was set to 1V peak-to-peak sine moving ridge with frequency=500Hz

Power supply was set to -12V and +12V and were connected to trap 4 and pin 7 of op-amp

Function generator was connected to input, Vin1. Signal at V- and end product signal, Vout were observed. Potentiometer was turned to the full to one way so that the end product wave form is minimal. Input and end product wave forms were observed. Measure was repeated by turning potentiometer to the full the opposite way so the end product wave form is maximize. Minimal electromotive force addition and maximal electromotive force addition in dubnium were calculated,

Vin1 was disconnected. Function generator was connected to input Vin2. Signal at V-and end product signal, Vout was observed. Potentiometer was to the full turned to one way so that the end product wave form is minimal. Input and end product wave forms were observed. Stairss were repeated by turning potentiometer to the full the opposite way so the end product wave form is maximize. Minimal electromotive force addition and maximal electromotive force addition in dubnium were found.

Function generator was connected to both input Vin1 and Vin2. Potentiometer was turned to the full counterclockwise. Signal at V and the end product signal, Vout were observed Input and end product wave forms were drawn. Measure was repeated by turning potentiometer to to the full clockwise. Observations were discussed. Minimum and maximal additions were found.

If potentiometer was set to focus on place, ascertained consequences at V- .

3-band in writing equaliser

Circuit of a 3-band equaliser was constructed with R11 = 3k? ,

Addition of the set base on balls filter was set to minimum ( the feedback resistor=0 ) .

Function generator was set to 1V peak-to-peak sine moving ridge at frequency=100Hz.

Power supply was set to -12V and +12V and was connected to trap 4 and pin 7 of op A.

Function generator was set to Vin.

Vout1, Vout2, and Vout3 peak-to-peak were measured. Frequencies as in Table 5.1 were repeated.

Each frequence, electromotive force addition,

Band base on balls filter was repeated at maximal addition ( feedback resistance at 10k ohm ) . Table 5.2 was filled.

Table 5.1 was observed. Gain vs. frequence ( log ) graph was plotted.

Gain vs. frequence ( log ) graph based on Table 5.2 was plotted. Derive provided by the filter was found.

Inverting summer amplifier

and potentiometer were measured utilizing digital multimeter.

Circuit with and was constructed.

Function generator was set to 1V peak-to-peak sine moving ridge with frequency=500Hz.

Power supply was set to -12V and +12V and were connected to trap 4 and pin 7 of op-amp

Function generator was connected to Vin1 and Vin2.

Input signal at the map generator ( probe channel 1 of CRO ) and end product signal, Vout ( investigation channel 2 of CRO ) were observed.

Input and end product wave forms were drawn. Voltage addition was calculated

Voltage follower

Function generator was set to 1V peak-to-peak sine moving ridge with frequence 500Hz.

Circuit for electromotive force follower was constructed.

Power supply was set to +12V ( maestro ) in series manner and was connected to trap 7 and -12V to trap 4 of 741 op A.

Function generator was connected as and was observed.

electromotive force addition, was calculated for each instance utilizing

Voltage degree index

Circuit was constructed with and

Function generator was set to 400mV peak-to-peak square moving ridge at f=50 Hz and

Voltage to cite electromotive force of each comparator was measured.

Function generator was connected to Vin. Detect that all LEDs are away. Input electromotive force was increased easy and end products of the comparators were observed when each LED brightens. Peak electromotive force was written down when each LED lights up. When the last LED is on, it was stopped.

Frequency of the input signal was decreased easy. The consequence was observed.

Consequences:

Crossfader:

When we turned the potentiometer to minimum, the Vin1 has maximal power

Av, min=20 log ( Vout/Vin )

=20 log ( 0.1/1 )

=-20dB

When potentiometer is tuned to maximum opposition, much power is absorbed by the resistance go forthing really small power for elaboration.

Av, max=20 log ( Vout/Vin )

=20 log ( 17/1 )

=24.6dB

3-band in writing equaliser:

Table 1: 3-band Graphic Equalizer Response ( Rf=0 )

60

1

0.00

0.04

0.14

?

-28.0

-17.2

40

1

0.00

0.20

0.20

?

-14.0

-14.0

20

1

0.00

0.30

0.34

?

-10.5

-9.4

15

1

0.02

0.40

0.40

-34.0

-8.0

-8.0

12

1

0.04

0.40

0.44

-28.0

-8.0

-7.1

10

1

0.06

0.42

0.54

-24.4

-7.5

-5.3

9

1

0.06

0.50

0.60

-24.4

-6.0

-4.4

8

1

0.10

0.60

0.60

-20.0

-4.4

-4.4

7

1

0.10

0.60

0.60

-20.0

-4.4

-4.4

6

1

0.10

0.60

0.60

-20.0

-4.4

-4.4

5

1

0.20

0.70

0.70

-14.0

-3.1

-3.1

4

1

0.20

0.70

0.70

-14.0

-3.1

-3.1

3

1

0.20

0.70

0.70

-14.0

-3.1

-3.1

2

1

0.26

0.64

0.60

-11.7

-3.9

-4.4

1

1

0.40

0.5

0.4

-8.0

-6.0

-8.0

0.8

1

0.40

0.44

0.40

-8.0

-7.1

-8.0

0.6

1

0.50

0.40

0.30

-6.0

-8.0

-10.5

0.5

1

0.50

0.34

0.26

-6.0

-9.4

-11.7

0.4

1

0.60

0.26

0.26

-4.4

-11.7

-11.7

0.3

1

0.54

0.20

0.20

-5.4

-14.0

-14

0.2

1

0.50

0.20

0.20

-6.0

-14.0

-14

0.1

1

0.34

0.14

0.14

-9.4

-17.1

-17.1

Freq

( kilohertz )

Vin, pp

Vout1

Vout2

Vout3

AV1

AV2

AV3

Table 2: 3-band Graphic Equalizer Response ( Rf=10k )

60

1

0.1

0.8

1.1

-20

-1.9

0.8

40

1

0.2

1.4

1.8

-14.0

3.0

5.1

20

1

0.3

2.6

3.4

-10.5

8.3

10.6

15

1

0.4

3.4

4.3

-8.0

10.6

12.7

12

1

0.5

4.0

5.0

-6.0

12.0

14.0

10

1

0.6

4.6

5.7

-4.4

13.3

15.1

9

1

0.7

5.0

6.0

-3.1

14.0

15.6

8

1

0.8

5.4

6.4

-1.9

14.6

16.1

7

1

0.9

5.8

6.6

-0.9

15.3

16.4

6

1

1.0

6.2

7.0

0.0

15.8

17.0

5

1

1.2

6.8

7.2

1.6

16.7

17.1

4

1

1.5

7.0

7.2

3.5

17.0

17.1

3

1

2.0

7.2

6.8

6.0

17.1

16.7

2

1

2.8

6.8

5.9

9.0

16.7

15.4

1

1

4.9

4.9

3.7

13.8

13.8

11.4

0.8

1

5.6

4.0

3.0

15.0

12.0

9.5

0.6

1

6.5

3.2

2.2

16.3

10.1

6.8

0.5

1

6.8

2.7

2.0

16.7

8.6

6.0

0.4

1

7.2

2.3

1.6

17.1

7.2

4.1

0.3

1

7.4

1.8

1.2

17.4

5.1

1.6

0.2

1

6.8

1.2

0.8

16.7

1.6

-1.9

0.1

1

4.6

0.6

0.5

13.3

-4.4

-6.0

Freq

( kilohertz )

Vin, pp

Vout1

Vout2

Vout3

AV1

AV2

AV3

Inverting summer amplifier:

R1=R2=R3=1k? , Rf=10k?

Vout= ( -Rf/R1 ) Vin1+ ( -Rf/R2 ) Vin2+ ( -Rf/R3 ) Vin3

= ( -10k/1k ) 1+ ( -10k/1k ) 1+ ( -10k/1k ) 1

= -30V

Av= Vout/Vin

= 30/1

=30V

Voltage follower:

Vin= 1V

Vout= 1V

= 1/1=1

Voltage flat index:

Vpp for LED1 to illume up is 4.8V

Vpp for LED2 to illume up is 2.8V

Vpp for LED3 to illume up is 1.2V

Vpp for LED4 to illume up is 0.56V

When frequence of input signal lessening easy, LEDs start eye blink.

Problems faced and solutions to it:

The sounds that come out from the talker are non loud plenty. To work out this, we can add a electromotive force follower before the talker to hike up the sound.

There are noises in the sound. When play the music, can non listen to the music clearly, there are many unwanted noise in it.

There is lading consequence during building. This may because the talker draws much current and power. So, to cut down lading consequence, we can add a buffer.

For electromotive force degree index circuit, when connect map generator to Vin, all the LEDs should turn off, but what observed is all the LEDs were on. This is because the legs of LEDs are opposite ( anode and cathode are incorrect in place ) . To work out it, change the place of the leg.

LED did non light up in sequence, this may due to resistor connexion job, or the connexion of wire. To work out this job, look into the connexion.

When concept electromotive force degree index to other constituents in audio sociable, LED did non light up when the input electromotive force additions, possibly this is because the electromotive force is non large plenty to turn on the LED. This job can work out by adding an excess electromotive force follower circuit.

Decision:

An audio sociable is an indispensable tool in working with audio. From utilizing a sociable in a unrecorded environment as a DJ, to making production work in a studio, the sociable is frequently the cardinal and cardinal nexus in your concatenation of equipment. Audio sociable controls the routing of audio lines to a finish device for playing or entering. It besides controls volume and other effects.

Audio sociable consists of 5 sub circuits, which are crossfader, 3-band in writing equaliser, inverting summer amplifier, electromotive force follower and electromotive force degree index.

We enhanced and improved our circuit by adding 2 electromotive force follower before the talker and 1 electromotive force follower before the electromotive force degree index. By adding the electromotive force follower, the noise was reduced so that we can acquire better quality sound and the electromotive force degree index works decently by turning on the LEDs visible radiation in sequence.

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