My amp's distorting

[idiotjohn]

Hi, recently I built a 12 watt amplifier for my mp3 player so that I could listen through speakers... I have finished building but when i turn it on with my mp3 player it distorts the music :-[ :-[ :-[ :'( :'( :'(. I can hear faint music in the back ground but mostly distortion :'( :'(. I am wondering what I may have done wrong that would make it distort?

I hope you can help. Attached is the page that has instructions for the circuit that came with the kit... It also has a picture or 2 or the circuit itself.



[move]Please Help :'([/move]

[audioguru]

This amplifier is for only one channel. You will need a 2nd amplifier and speaker for the other channel. Maybe you have the input from the MP3 player connected so this amp plays the difference between both channels that sounds weird.

Do You have a 4 ohm speaker connected at pin 4 and pin 6 without either connected to ground? Measure their DC voltage. They should be 6V.

Do ypu have a 12V power supply that can supply 1.8A or more?
Does your MP3 player have a volume control? The article is wrong, this amp needs only 40mV of signal for full output so turn down the volume control.

[audioguru]

You sketched an extra 224 capacitor at the amp's input. Are you shorting together both channels from your MP3 player? The short might have damaged the MP3 player. A 10k resistor from each channel would combine them together without causing damage.

[idiotjohn]

I have combined both channels into 1 in my plug that inserts into my mp3 player. Ignore the sketching! I have no idea what you are talking about!

[audioguru]

I have combined both channels into 1 in my plug that inserts into my mp3 player.

Then you are shorting together both outputs and maybe are causing damage to the MP3 player.

You should combine the outputs with isolating resistors:
1) Connect a 10k resistor to the output of the left channel.
2) Connect another 10k resistor to the output of the right channel.
3) Join the two resistors and connect the joint to the amplifier's input capacitor, and connect the cable's ground to the amplifier's ground.

Try a headphone to see if the MP3 player is damaged.

[idiotjohn]

I have combined the two.... See below. Could you just tell me what I might have done wrong? I have tryed recharging my batteries... Could it be That I am running it from 9.6 V rather that 12V??? Could it be that the copper wire that I am using dousent have enough gauge?

I would like to understand what you are saying... could you please use slightly simpler words or explain what you mean. I am not a great electonics person.

My mp3 player isn't damaged

[audioguru]

Your combining circuit is correct but has 100 0hm resistors for a headphone jack output.
My recommended combining circuit is the same but uses 10k resistors for either a headphone jack or a line-level jack output. A line-level output is shorted by only 100 ohms.

With a 9.6V supply, the amp produces 7W into a 4 ohm speaker or 4W into an 8 ohm speaker. It will be very distorted if the volume is higher.

[mvs sarma]

please see the BTL aplifier application in the attached Philips Application note.
the electrolytic cap on pin 3 is not shown in BTL application pl check

also the input should be 1v line in equivalent  for proper audio output

as audioguru already suggested try pre setting the vol cont of the said MP3 player for proper input to the power amp.

next to this , perhaps i fear whether the IC is OK or Not ?

tda1519a.pdf

[audioguru]

the electrolytic cap on pin 3 is not shown in BTL application pl check

Pin 3 is called "Supply Voltage Ripple Rejection" and is the half-supply-voltage-reference. It needs a capacitor to reduce ripple as shown in figure 4.

also the input should be 1v line in equivalent