Help with TDA2822M amplifier circuit, (NOISE)

[markb2003]

Hi all, Hoping anyone of you could help me out a bit!
Im"kind-of" new to electronics(WELL, Building electronics), been "playing with electronics FOREVER!
Anyways, I've made an audio amplifier(using TDA2822M IC)Going by the datasheet schematics!
well, making the circuit was'nt so hard(after scrounging All my parts, and a little piece of board)
My problem is that it has ALOT of excessive noise when hooked up to my computer, but NO excess noise when hooked to my MP3 player!!!
Please, HELP!!!
Thank you!!!

 

[audioguru]

Describe the noise. Is it low frequency mains hum (because the input cable is not shielded or because of a ground loop) or is it high frequency hiss?

 

[markb2003]

Its kind of a low frequency hiss?!?!?! (It is NOT a "HUM", but it isnt high frequency either)
Im thinking it MAY be because I've got the power coming from a Computer's USB port!
Is there some kind of a "filter" I could "make" to put on the power leads, for that?... maybe?
Ill try running it from a 9 volt battery, SEE what that does!(Ill re-post my findings)
Thanks for your help!

 

[markb2003]

Could you "describe" to me basically what a ground "loop" is, Or is it "exactly" what it sounds like?!?!?!?

 

[markb2003]

Also, I forgot to mention, The left amplifier circuit seems comsiderable "louder" than the right(even with the "static")

 

[MikeMl]

Run it on an external 5V supply as a test. That will eliminate the "ground loop" that exists between the where the 0V point for the USB connector is taken on the motherboard, and where the sound card audio ground is on the mother board. The USB jack was never intended as a source of power for audio devices, PERIOD!

 

[audioguru]

The output power of each channel of a TDA2822M stereo amplifier IC with a supply that is only 5V is only 0.16W at clipping into an 8 ohm speaker. 0.16W is a very small amount of power.

 

[markb2003]

The static WAS from the USB port, I have that figured out! (hooked up the 9 volt battery and works GREAT!!!)
(Is there a way to make a "filter" to "HELP" this?)

(MikeML: The USB jack was never intended as a source of power for audio devices, PERIOD!), If that is true than how do loads of "store-bought" computer speakers get they're power from USB ports without having the static?!?!?

audioguru, The TDA2822M MAY give out a "SMALL" amount of power but, its better than nothing! Also it seems decently loud when pushing a 3 Ohm speaker!

Also, How would I reduce the volume?, I mean What resistor value would i use? (I would replace the 10K Ohm resistor at each input with X resistor, correct?(whatever the value may be!)
If im not mistaking, I'd use a "Larger" Ohm resister for reducing volume?!?!?! or the other way round?

 

[markb2003]

Even with the "NON-computer" power(I.E. 9 volt battery) the left side audio circuit is still a bit louder than the right!

 

[audioguru]

Bass frequencies will be at a low level if the speaker is only 3 ohms and the output capacitor is only 470uF. Use 1000uf or 2200uF.

An audio amplifier uses a audio-taper (logarithmic) volume control to adjust its volume. Stereo volume controls have the two potentiometers joined onto one shaft.
The 10k input resistors shown on the datasheet for the TDA2822M are replaced with the stereo volume control. Each channel of a volume control has two resistors in series making a voltage divider, not just a single resistor.

 

[markb2003]

I understand the low frequencies, but I dont understand how (when my circuit is EXACTLY the same for both channels) one channel could be louder, than the other!
I think thats the most confusing part for me!

 

[audioguru]

Maybe one of the 100uf or output capacitors is bad which will cause one channel to have less volume.
Swap the two capacitors to see if the low volume goes to the other channel.

 

[MikeMl]

The static WAS from the USB port, I have that figured out! (hooked up the 9 volt battery and works GREAT!!!)
(Is there a way to make a "filter" to "HELP" this?)

(MikeML: The USB jack was never intended as a source of power for audio devices, PERIOD!), If that is true than how do loads of "store-bought" computer speakers get they're power from USB ports without having the static?!?!?

They use a transformer-coupled switching supply, which provides d.c. isolation, and effectively breaks the ground loop.

I have dealt with this issue before, where a computer-sound card interface Line-audio out and Line-audio input must be audio-transformer coupled to break the ground-loop between the sound card and external audio equipment. Google "Rig-Blaster" interface.

Just go get an unused several volt D.C regulated wall-wart charger from an old cell phone to power your audio amp...

 

[markb2003]

well, I believe i've fried the TDA2822M IC... I've got a TEA2025B im going to try now! HOPEFULLY that project will turn out better, and last longer!!! thanks ALOT for all of your help!!!

 

[markb2003]

Ok, Even though the "old" TDA2822M IC (burnt up), I've managed to scavange a TDA2822 from an old alarm clock!!!
Could ANYONE possibly tell me the difference?!?!?
What changes id have to make IF any?
Thanks again!!!

 

[audioguru]

The TDA2822M is in an 8-pins case so it can dissipate only 1W.
The TDA2822 is in a 16-pins case so it can dissipate 1.5W.
Look on the datasheet to see which pins are which.

 

[markb2003]

The TDA2822 out of the alarm clock is only 8-Pin?!?!?!?! It works fine!!! same EXACT wiring as the TDA2822M!!!
In my opinion its actually a bit better!!! Not as much distortion, Still have the problem with the volume though!!!
But as long as I keep my computer volume WAYYY down, its fine!!!

 

[audioguru]

Maybe a Chinese company has copied ST Micro's TDA2822M and called it a TDA2822 by mistake.

 

[markb2003]

Idk, its working now though!!! So, im just going to leave it alone! make a different enclosure for the whole system(The Amp{AND components} and Two 2.5" 3OHM speakers)
Anyways, Thank you SOOO much for all of your help!

 

[markb2003]

IDK if this is going to work or not, BUT I've TRIED attaching some pics of my amp layout(from myspace)
IF you CAN see them, They are FRONT and BACK of the "board"!!!


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