TDA1557 issue

[nchaaa]

So, as some of you advised me, I have used ceramic capacitor for signal input (instead of plastic ones) and now it works well !
I have read for a last time carefully the datasheet, and there is no mention about a specific material for the input capacitors, so I am a bit angry against Philips.
Anyway, I have made listening tests on good reference speaker, and although this is not hifi purpose, the quality is not so bad at low-mid volume.
If found there is a bit too much noise when no signal, do you know how I can reduce this background noise ? (this is not hum, but broadband background noise)

 

[audioguru]

The TDA1557 is noisy because its voltage gain is 400.
The TDA1554 has much less noise because its voltage gain is only 20.

EDIT:
A ceramic audio coupling capacitor causes distortion.
An electrolytic audio coupling capacitor causes less distortion.
A plastic audio coupling capacitor causes no distortion.

 

[wizard]

nchaaa,
You have said that you could not opearte it WITHOUT any input!!
Now you say it works bye those ceramic caps?
I Remember that I have had a similar problem using those electrolytic caps, but the problem was just for one device, I did not have any problem when used it as an amplifier for a radio cassate. But I had that problem when I connect the amplifier input to the output of the preamplifier. I had no problem when I had an input with a ceramic caps which became in series with that electrolytic cap(You know that there would not be any problem when I replaced that electrolytic cap with a 104 ceramic one. When there was not any input the amplifier was ok and had the hmmm noise when I put my finger on the input pin. I am wondering why did not use that test!?

Don't forget to put a 104 ceramic cap across the supply source too.

 

[whiz115]

A ceramic audio coupling capacitor causes distortion.

can you also tell us why?

 

[Hero999]

A 4.7µF electrolytic is fine on this occasion it's so grosly oversized the distortion will be negligible so there's no need for more expensive polyester capacitors.

 

[audioguru]

A ceramic capacitor changes its value with voltage changes. So it is a good coupling capacitor for half the wave and a poor one for the other half of each wave. That makes even harmonics distortion.

Hi Hero,
I don't count pennies when designing circuits. A plastic capacitor costs almost nothing and has no distortion so I use it. It has the correct value to reduce frequencies that I don't want.

 

[a.Mousavi]

help!!

hello
i know its unrelated to the topic and sorry about renewing an old thread but please be kind to help me to find my answer <3
ive heard the tda1557 is discontinued or atleast not available in my contry anymore . so the question is whats exactly same to replace with tda1557 ?

 

[audioguru]

hello
i know its unrelated to the topic and sorry about renewing an old thread but please be kind to help me to find my answer <3
ive heard the tda1557 is discontinued or atleast not available in my contry anymore . so the question is whats exactly same to replace with tda1557 ?

Why didn't you start your own thread??
Philips used to have more than 30 amplifier ICs for cars. But since they changed their name to NXP Semi many ICs are not made anymore.
Recently ST Micro made the TDA7377A IC that was almost the same as the TDA1557 but it is also not available anymore.

The TDA7240A is a bridged single amplifier IC and two can be used to make a stereo car amplifier. The output power is almost the same as the old TDA1557. The TDA7240A is also not available anymore.

 

[a.Mousavi]

humm thanks for reply but if none of those are available , then whats the solution ?

 

[audioguru]

humm thanks for reply but if none of those are available , then whats the solution ?

Chinese manufacturers make most electronic products today.
I recently learned that Creative Sound Blaster products for computers is a Chinese company (I thought it was American). They use Chinese amplifier ICs that are not available over here.

 

[kanchan kumar dhir]

i have made two tda1557 amplifierbut when i connect two amplifer paralally to get 4 out put,it creats more noise,,,,,plz telll how i remove the noise from the aplifier...

 

[audioguru]

i have made two tda1557 amplifierbut when i connect two amplifer paralally to get 4 out put,it creats more noise,,,,,plz telll how i remove the noise from the aplifier...

You are not supposed to connect two of the amplifiers in parallel.
Each TDA1557 IC is a stereo (two outputs) amplifier IC. I do not know why and I do not know how you connected them in parallel.

You forgot to show your schematic, and you did not describe the noise (hiss? distortion?).