4558 ic circuit diagram for simple audio amplifier

[rajaram04]

Hello sir

For ic 4558 i am not getting any audio amplifier circuit diagram here or anywhere though i need a very simple one , please help . .thanks

 

[godfreyl]

The RC4558 is a dual opamp. The datasheet says each half is electrically similar to a uA741. So you can use it in any 741 circuit.

 

[rajaram04]

The RC4558 is a dual opamp. The datasheet says ieach half is electrically similar to a uA741. So you can use it in any 741 circuit.

okk ! well is it a good one as an audio amp ? or suitable for short term applications like head phone amp.etc ?????

 

[Audioguru]

The datasheet for the 4558 shows that each of its opamps can drive a 10k load very well and drive a 2k ohms load not good but not too badly.
It is not a stereo power amplifier. Instead it was designed to be the preamp in a record player or tape player that drives the inputs of a power amplifier.

What is the impedance of your headphones? 2k ohms or more? I doubt it because most headphones today are 32 ohms.

 

[rajaram04]

The datasheet for the 4558 shows that each of its opamps can drive a 10k load very well and drive a 2k ohms load not good but not too badly.
It is not a stereo power amplifier. Instead it was designed to be the preamp in a record player or tape player that drives the inputs of a power amplifier.

What is the impedance of your headphones? 2k ohms or more? I doubt it because most headphones today are 32 ohms.

and how to measure the impedance of head phone ? its an earplug actually by nokia

 

[Audioguru]

and how to measure the impedance of head phone ? its an earplug actually by nokia

Impedance is resistance to an AC signal. Measure its resistance with a multimeter. Its resistance will be a little less than its impedance.
The resistance of the headphones (earplug kind) for an iphone is 33.4 ohms for each ear and it needs a little power amplifier to drive it.

 

[rajaram04]

Impedance is resistance to an AC signal. Measure its resistance with a multimeter. Its resistance will be a little less than its impedance.
The resistance of the headphones (earplug kind) for an iphone is 33.4 ohms for each ear and it needs a little power amplifier to drive it.

hmm i tested but maximum range of 2000k on a multimeter i got no reading . .

 

[Audioguru]

hmm i tested but maximum range of 2000k on a multimeter i got no reading . .

Then your earphones must be the 60 years old "crystal" (piezo) kind. In the WEST, headphones are the modern "dynamic" (coil and magnet) kind.

Here is a list of earphone types: https://en.wikipedia.org/wiki/Headphones

 

[FvM]

Then your earphones must be the 60 years old "crystal" (piezo) kind

At those days, Nokia has been making rubber boots as far as I know. There must be a different explanation, e.g. incorrrect measurment.

 

[godfreyl]

hmm i tested but maximum range of 2000k on a multimeter i got no reading . .

Now try a more sensible range like 200 or 2K.

 

[Audioguru]

hmm i tested but maximum range of 2000k on a multimeter i got no reading . .

Because the reading is very low? That is normal on such a high range.

2000k is 2 million ohms. A 32 ohm earphone would measure almost zero.
But on a range of 200 ohms maximum then the 32 ohm earphone would measure about 30.

 

[rajaram04]

ohh haha lots of amazing discussions & explanations , well i got that in range of 200 ohms but i everytime i connect the meter & getting diffrent results like sometimes 15 ohms sometime 28 ohms sometime 32 ohms then 40 ohms n so on . . dont know why , but maximum time i got 24 & 28E

 

[Audioguru]

Finger prints on the meter probes and earphone plug cause the very low resistance to change. Your earphone are probably 16 ohms for each ear so you need a little stereo power amplifier to drive them.

I looked in Google Images for Earphones Amplifier Circuit With Opamp and found hundreds of circuits.

 

[rajaram04]

Finger prints on the meter probes and earphone plug cause the very low resistance to change. Your earphone are probably 16 ohms for each ear so you need a little stereo power amplifier to drive them.

I looked in Google Images for Earphones Amplifier Circuit With Opamp and found hundreds of circuits.

hmm ya i too got many & randomly selected here as a compact one but transistor is the issue in following diagram



please help me in implanting an equivalent for those two

rest of the component is with me . . .thanks

 

[FvM]

The circuit will work with any pair of medium power NPN/PNP transistors, let's say > 1 W.

 

[rajaram04]

The circuit will work with any pair of medium power NPN/PNP transistors, let's say > 1 W.

any example for commonly available ??????

i am choosing bc547 & bc557 for now . . please help

 

[Audioguru]

The low current BC547 and BC557 transistors will blow up if the output of the amplifier is shorted when it is playing loudly.
I would use TIP31 and TIP32 medium power transistors that will survive.
This amplifier might produce enough loudness in earphones to deafen you so maybe you will need an attenuator resistor in series with each earphone.

 

[rajaram04]

The low current BC547 and BC557 transistors will blow up if the output of the amplifier is shorted when it is playing loudly.
I would use TIP31 and TIP32 medium power transistors that will survive.
This amplifier might produce enough loudness in earphones to deafen you so maybe you will need an attenuator resistor in series with each earphone.

hm i see . . ya kk got it . . so what about substitute or say equivalent for TIP31 etc ?

 

[Audioguru]

I am not in your country so I do not know what is available there. I can buy ANYTHING here.

 

[godfreyl]

Any of these transistor pairs should be good:

NPN / PNP
mje340 / mje350
bd139 / bd140
2sc4793 / 2sa1837
2sc3421 / 2sa1358