audio amplifier circuit using 4440 ic............

[debajyoty.roy]

Hi i build a audio amplifier using LM4440 ic..my problem is there is a huming sound comming out from the spekr...when i touched the ground line while my feets are in the floor the noise is gone....how can i solved the problem????pls hlp me..thnks.

 

[ftsolutions]

It is most likely that you are hearing hum from the AC mains power, either coupled through your power supply circuit or being picked up as noise by a nearby fluorescent lamp. You will have to post some pics or schematic of your circuits for us to offer specific help.

 

[crutschow]

You might try connecting the ground line to the AC mains safety ground pin (not neutral) or to earth ground (or listen to the music while touching the ground line ).

 

[Audioguru]

There is no LM4440 IC. Maybe you have an LA4440 amplifier IC that was made by Sanyo and is now discontinued?

Amplifier hum can be mains pickup by an unshielded input cable or many messy wires on a breadboard.

 

[debajyoty.roy]

ths cicuit i followd..........i think the prblm in the power supply..it is just an ordinary one consisting with bridge recti with two 1000uf cap filter ckt and a 7812 regu.....what shoud i do to eliminate that noise.......

 

[Audioguru]

Maybe your 7812 regulator IC does not have an input voltage high enough, 14VDC minimum? Then the transformer must be at least 12VAC. The output of a properly working 7812 has no hum.


This amplifier circuit has an extremely high gain of 700 times so a tiny input signal will be produced at its output. Then using a shielded audio input cable is very important.

Pin 2 is the live audio input, pin 3 is the input ground and pin 4 is for muting. The shield of the audio input cable should be connected to pin 3.

 

[BradtheRad]

Power the amplify from a battery temporarily. If the hum is gone, then your power supply needs more filtering.

If the hum stays, then your signal-carrying leads need to be shorter, or need shielding, etc.

It is common for hum to decrease when you touch a circuit ground and an earthed ground simultaneously.

 

[debajyoty.roy]

Power the amplify from a battery temporarily. If the hum is gone, then your power supply needs more filtering.

If the hum stays, then your signal-carrying leads need to be shorter, or need shielding, etc.



It is common for hum to decrease when you touch a circuit ground and an earthed ground simultaneously.

using battery there is no noise...so i think problem in power supply..so how can i improve my supply???

 

[Audioguru]

Please post the schematic of your power supply. We must know the output voltage of the transformer.
Did you use a solderless breadboard to make the amplifier?

 

[debajyoty.roy]

Please post the schematic of your power supply. We must know the output voltage of the transformer.
Did you use a solderless breadboard to make the amplifier?

its very simple one....tranformer is 12v,1amp......
no i use a vero board.....

 

[dick_freebird]

A simple diode bridge makes a lot of hum with any
load at all. If you have headroom to burn then a
linear regulator could help, but I think the better
solution is for you to find a cheap 12V buck module
that switches at least 50kHz so that main and
subharmonic tones are out of the audio band. You
will also get superior efficiency vs any linear reg.

 

[Audioguru]

Your power supply makes NO HUM when it is powering the amplifier that is not playing loudly.
The amplifier rejects most power supply hum anyway.

The hum is probably from the charging current of the 2200uF filter capacitor getting into the input ground of the amplifier. This does not happen if a STAR GROUND is used.