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A mono sound system ( Filter Designing) * NEED URGENT REPSONSE *

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meetheboss

New Member
Hello ppl , i m doing my bachelors in electrical eng . and i m in 3rd year of my engineering .. i have been assigned a project to design an electric filter whose details are as follows :-



First Order - Admittance Model - Active Element(741 IC)

Bass
Gain :
±15dB
Frequency(Cut-off) : 500Hz

MID
Gain :
±15dB
Frequency : 500-4500 Hz


Treble
Gain : ±15dB
Frequency : 4500 - 20,000 Hz


I have been trying to work on the Bass which must be a low pass filter according to my calculations i have been able to get the following circuit which is implemeted on Multisim as shown below ...



but when i tried to make this filter specifications on Filter Pro its making for 2nd order whereas mine is 1



please correct me if i m wrong somewhere and tell me what changes have to be placed ...

2ndly guide me how to add this ±15dB Gain in this circuit ....

will ask for this MID & Treble laterz
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
It's somewhat disturbing to find a third year student defgree student who knows so little?.

But your ideas so far are completely wrong - your assignment isn't a 'filter' it's a simple tone control circuit - try googling for "baxandall tone control", there are loads of versions with either two or three controls, usually three for an audio mixer.
 

meetheboss

New Member
well yes may be this is the right definition of the project .... but i have this Electric filter as a subject ... i have been given this concept abt designing this circuit
 

crutschow

Well-Known Member
Most Helpful Member
A first order filter is as simple you can make. It typically consists of one resistor and one capacitor or one inductor. Filter Pro is made for the design of active filters of 2nd order or greater.

The gain can be provided by an op amp circuit, which can also provide the filter functions. Look at http://www.electro-tech-online.com/custompdfs/2009/04/sloa058.pdf for more information.
 

Sceadwian

Banned
Try using google, first order filters are not exactly complicated. You should find plenty of circuits out there for high/low and bandpass.
 

crutschow

Well-Known Member
Most Helpful Member
In your simulation:

100M ohm input resistor is way too high for a 741 (or just about any op amp). It should be no more than about 50k ohm.

Your power supply is not grounded. You need a plus 15V and a minus 15V supply with each supply connected to ground.

It looks like you've connected the offset adjust pins to ground. They should be left open.
 
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