TDA2822 ic - audio quality

[Javid.zare.s]

Hi
Ive been working with a headphone project and i managed to put a tda2822 in it az amplifier so it wont get lot of energy from my phone...
Ive tested one side of headphone before final assembly ... Terrible sound... I always get a hiss sound in the background of music playback...
Can i get ride of this hiss ??
3.7v battery , no pcb soldered all together

- - - Updated - - -

i cant edit post so adding schematics here:
as u see i replaced 470uf capacitor with 100uf
4.7ohm with 2ohm resistor
and at last no 10k resistor at the inputs
(ive not added 100uf on the power input yet)

 

[c_mitra]

First you need to determine whether the hiss is coming from the input OR is being produced by the circuit.

You need to short the input (and try a 10K resistor) and see if the hiss is still present.

Next you will need to decide whether it is a stray pick up or internal to the circuit.

 

[Javid.zare.s]

First you need to determine whether the hiss is coming from the input OR is being produced by the circuit.

You need to short the input (and try a 10K resistor) and see if the hiss is still present.

Next you will need to decide whether it is a stray pick up or internal to the circuit.

ive tested without any input to circuit and found sth odd!!!
if i touch the {C} wire which circuit IS NOT connected to it the louder hiss comes up!!!
{L}left and {R}right channels are connected to the jack but {C} isnt
like this picture:


again no mp3 player is connected to circuit
sample voice:
**broken link removed**

 

[Javid.zare.s]

i think its grounding issue but its on battery why im facing this ?!!!!

 

[c_mitra]

Try to bypass both L&R (audio input) with 100 nF to ground.

 

[Javid.zare.s]

Try to bypass both L&R (audio input) with 100 nF to ground.

yep thanks, the odd sound is gone by placing 1uf cap but very little hiss is still there...i cant hear it far away but if i wear headphone its easily noticable.
any suggestion?

 

[Audioguru]

You forgot to read the datasheet of the old TDA2822. It says it was made as the amplifier to drive speakers in a cassette player THAT IS NOT HELD TO YOUR EARS!
Of course it has hiss and is not hifi because it is cheap. Websites where people talk about making good headphones amplifiers use low noise audio opamps driving output transistors. The best website was called Headwise but it has closed. Its headphones amplifiers can be found on the internet, one was called Cmoy.

The TDA2822 MUST have a resistor or a sound source that is connected to ground to bias its inputs properly. On your recording I did not hear a voice or music, I heard only loud noises and humming-buzzing.
The humming and buzzing is probably caused by your unshielded input wires. Amplifier inputs ALWAYS must use shielded audio cables, not ordinary wires.
Connecting capacitors from the inputs to ground simply kills all high frequencies then everything will sound muffled like an AM radio.

 

[c_mitra]

the odd sound is gone by placing 1uf cap but very little hiss is still there...i cant hear it far away but if i wear headphone its easily noticable.

This says that the hiss is coming from external sources;

1. no, not 1uF use 0.01uF or even 100nF (in parallel to th 10K already there)

2. Your input connection is not shielded; use a shielded cable

3. Use another 100nF ceramic cap at pin 8 (in parallel to the existing cap)

Hope the things will improve but part of the disease is internal.

 

[Javid.zare.s]

You forgot to read the datasheet of the old TDA2822. It says it was made as the amplifier to drive speakers in a cassette player THAT IS NOT HELD TO YOUR EARS!
Of course it has hiss and is not hifi because it is cheap. Websites where people talk about making good headphones amplifiers use low noise audio opamps driving output transistors. The best website was called Headwise but it has closed. Its headphones amplifiers can be found on the internet, one was called Cmoy.

The TDA2822 MUST have a resistor or a sound source that is connected to ground to bias its inputs properly. On your recording I did not hear a voice or music, I heard only loud noises and humming-buzzing.
The humming and buzzing is probably caused by your unshielded input wires. Amplifier inputs ALWAYS must use shielded audio cables, not ordinary wires.
Connecting capacitors from the inputs to ground simply kills all high frequencies then everything will sound muffled like an AM radio.

Wow lot of information!! Thanks dude
So I think im not gonna continue with tda2822 , but also ive bought lot of lm386 can i use them for each channel Or its again noisy ?

This says that the hiss is coming from external sources;

1. no, not 1uF use 0.01uF or even 100nF (in parallel to th 10K already there)

2. Your input connection is not shielded; use a shielded cable

3. Use another 100nF ceramic cap at pin 8 (in parallel to the existing cap)

Hope the things will improve but part of the disease is internal.

I didn't use resistor on input , I thought i can place a potentiometer later. , about shilding the noise is the without music playing ove done anything but it simply doesn't shut that noise :/

 

[Audioguru]

The LM386 amplifier is also cheap and is made to play audio through a speaker (that is not held to your ears), so you will hear its hiss in headphones. You need an audio amplifier rated for LOW NOISE.
An ordinary unshielded wire is an antenna that picks up the mains hum radiated from electrical wiring all around you and many other kinds of interference. Look at the shielded audio cables used for the connections between a music source (MP3 player?) and an audio amplifier, they have a signal wire surrounded by a shield wire.

 

[c_mitra]

I didn't use resistor on input , I thought i can place a potentiometer later. , about shilding the noise is the without music playing ove done anything but it simply doesn't shut that noise :/

In post #1, I see 10K resistors to ground.

If the input is shorted but the noise is still there, that suggests that the noise is not external pickup.

 

[Javid.zare.s]

The LM386 amplifier is also cheap and is made to play audio through a speaker (that is not held to your ears), so you will hear its hiss in headphones. You need an audio amplifier rated for LOW NOISE.
An ordinary unshielded wire is an antenna that picks up the mains hum radiated from electrical wiring all around you and many other kinds of interference. Look at the shielded audio cables used for the connections between a music source (MP3 player?) and an audio amplifier, they have a signal wire surrounded by a shield wire.

O.k. So now i got it! Iill search for a cheap and low noice amp if i could find one :/ but a have a question can lm386 really deliver 200 watts with a little modification? Do i need heatsink?

In post #1, I see 10K resistors to ground.

If the input is shorted but the noise is still there, that suggests that the noise is not external pickup.

Yea yea youre right , i didnt had that resistor so i said why should i use it but now i know

 

[betwixt]

have a question can lm386 really deliver 200 watts with a little modification? Do i need heatsink?

Yes, no problem. Forced liquid nitrogen cooling is all you need.

Brian.

 

[Audioguru]

Don't you know arithmetic?
200W into 8 ohms is an AC signal that is 40V RMS. Its peaks are 56.6V and there is a positive peak and a negative peak so the total is 113.2V. The 56.6V peaks causes a peak currents of 7.1A. The datasheet of the LM386 shows that its performance is poor with a supply more than 9V (its maximum allowed supply is 12V for most and 18V for one) when its output power into an 8 ohm speaker is only 0.56W because then its output swing is only 3V peak and its output current is only 0.375A peak.

Why not use a real power amplifier IC like an LM3886 (56W into 8 ohms) where 4 of them can be used be bridged and paralleled for 200W into 8 ohms as shown on National Semi App Note 1192. Of course a pretty big heatsink is needed because these linear amplifiers dissipate about the same amount of output heat (200W) as the output power (200W).

Texas Instruments and other manufacturers make class-D switching audio amplifier ICs that are very efficient and do not need a huge heatsink. But they have millions of tiny little legs to solder somehow. Some tiny amplifier ICs don't have any legs, instead they have "bumps" on the bottom and are soldered to a pcb in an oven.

 

[Javid.zare.s]

Don't you know arithmetic?
200W into 8 ohms is an AC signal that is 40V RMS. Its peaks are 56.6V and there is a positive peak and a negative peak so the total is 113.2V. The 56.6V peaks causes a peak currents of 7.1A. The datasheet of the LM386 shows that its performance is poor with a supply more than 9V (its maximum allowed supply is 12V for most and 18V for one) when its output power into an 8 ohm speaker is only 0.56W because then its output swing is only 3V peak and its output current is only 0.375A peak.

Why not use a real power amplifier IC like an LM3886 (56W into 8 ohms) where 4 of them can be used be bridged and paralleled for 200W into 8 ohms as shown on National Semi App Note 1192. Of course a pretty big heatsink is needed because these linear amplifiers dissipate about the same amount of output heat (200W) as the output power (200W).

Texas Instruments and other manufacturers make class-D switching audio amplifier ICs that are very efficient and do not need a huge heatsink. But they have millions of tiny little legs to solder somehow. Some tiny amplifier ICs don't have any legs, instead they have "bumps" on the bottom and are soldered to a pcb in an oven.

Ok so its not a great idea to use these amplifiers ,what do you suggest for those tiny speakers :/

 

[c_mitra]

Ok so its not a great idea to use these amplifiers ,what do you suggest for those tiny speakers :/

You should focus on the principle and learn from the grounds up. Making a *good* power supply for a 200W Audio Amplifier is also not trivial. 200W is a lot of power.

 

[Audioguru]

First you asked about hiss on a headphones amplifier that uses a cheap, small speaker amplifier. Then you asked about a 200W monster amplifier.
Do you want a low noise low power headphones amplifier or a 200W monster speaker amplifier?

 

[Javid.zare.s]

First you asked about hiss on a headphones amplifier that uses a cheap, small speaker amplifier. Then you asked about a 200W monster amplifier.
Do you want a low noise low power headphones amplifier or a 200W monster speaker amplifier?

No i asked for 200w power just for extra information ,no one is gonna put 200w into a headphone!
Im still looking for a way to shut the hiss or find a new uncomplex amp chip

You should focus on the principle and learn from the grounds up. Making a *good* power supply for a 200W Audio Amplifier is also not trivial. 200W is a lot of power.

Yea and a lot of heat headphone will be on fire , i just asked this for a 2000w speaker i have and defenetly not for a 0.5watt headphone ,fortunetly ive found a sheilded cable to use on inputs , ive got it form an old castte player

 

[Audioguru]

Im still looking for a way to shut the hiss or find a new uncomplex amp chip

The Cmoy portable headphones amplifier I mentioned in post #7 uses the OPA134 single or OPA2134 dual audio opamp. It has extremely low distortion and noise and a minimum supply of about 5.7V when driving a 33 ohm headphone to 0.5V. Some people add a complementary pair of output transistors as emitter-followers to boost the output current to drive 8 ohm headphones. The output transistors are included inside the negative feedback loop of the opamp so their distortion is much less.