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Hello, please wake up!
An LM368 is a voltage reference IC.
An LM386 is a little power amplifier IC.
They are completely different.
Which one did you order?
I hate to dig up and older thread, but this was exactly what I was after.
I have an AM/FM hand held radio that makes use of the TDA2822 amplifier, And I have the same intentions, to run an MP3 output into this device, and power a small 4 or 8ohm speaker.
The speaker is a cheap $6 piece from wall mart for car audio. It could be 8ohm but I think it's 4 ohm.
The only specs are 8 Watts RMS @ 1Khz and 25 watts max.
The radio runs 4.5V
What I would Like to find out from you,
1) Where Do I tie into the existing input for this Amplifier? Can it be done directly to the input or will it need a resistor to step down the input signal?
2)What needs to be done to disable the existing Radio reciever? Can I simply sever the existing input circuit?
The TDA2822 is already bridged according to the schematics I've looked over.
I apologize for any and all short comings. I've never attempted any work like this, only what training i've had for automotive electrical systems.
A crystal radio is not sensistive because it doesn't have an RF amplifier nor a very high gain IF amplifier. Its loudness is determined by how strong is the signal because it doesn't have automatic-gain-control like a real AM radio.
So it needs to have an AM radio station right next door or have a long wire antenna and an earth ground.
This circuit has an LM386 power amplifier amplifying a crystal radio to drive a speaker.
My previous post is 2 months late because this site took me to the 1st page instead of to this 2nd page.
You need two resistors to mix the left and right channels of the MP3 player into mono. Then add a switch to the radio's volume control so that you select the radio or the MP3 player to feed the volume control.
The TDA2822 is not supposed to drive a 4 ohm speaker when it is bridged but since your battery voltage is so low then no harm will be caused.
No.
The radio must be disconnected from the volume control. Then the outputs of the MP3 player each feed a resistor of 4.7k or 10k. The resistors join at the volume control.
The resistors separate the two audio power amplifiers in the MP3 player so they are not shorted together that might damage them. They reduce the level a little. The volume control can reduce the level a lot if it is necessary.
I removed a 4.7K ohm resistor from the board and placed it inline with the volume control and my line in. With the ear phones, I can barely make out what the song is. There is alot of distortion. I haven't tried the speaker yet.
Does this mean I should go to a 10Kohm? I don't have one available at the moment to try.
I just have this hooked to line level from the computer right now.
The line output from your computer is probably at a level that is completely different from your MP3 player.
Since you have a lot of distortion then simply turn down the volume control.
The volume control will reduce the signal to 1/10th when it is turned down from max to half.
Changing the 4.7k resistor to 10k won't make much difference.
Where does the ground lead for my input wire need to be connected on the board? I have it on common ground for the pcb right now.
I'm using the wires from the earphones provided with the radio.
Distortion might not have been the right term for what this is doing... If i didn't know the songs, there would be no way to tell what is playing. The volume cuts all the "noise" out, rather than providing any clarity.
I don't know why you are using wires from earphones. The cable from the MP3 player to the amplifier must be shielded audio cable like is used to connect hi-fi components together. Unshielded wires pick up interference and mains hum.
The ground lead from the MP3 player' outputs must connect to the ground of the amplifier circuit. The volume control also probably has one of its 3 legs connected to ground.
An amplifier with an input signal that is too high clips the top and bottom of the waveform off. Then the output is square-waves instead of music. Clarity is gone and there is severe distortion. Guitar players call it "fuzz".
Maybe you connect the resistors from the MP3 player to the wrong leg of the volume control.
I used the earphones because they were readily available.
Currently I'm using only one line out from the MP3 player.
I attatched signal-in to the leg opposite the common on the volume POT, with the center (wiper) left intact to the TDA2822
Full audio spectrum isn't required from this. It will be a coyote call when i'm done. Right now it can't even be used for that.
The noise has an audible rhythm but that's it. It's way beyond clipping.
I hate to be a PITA.. I'm just trying to think through this and it has me stumped.
I did at one point have 6V connected. The IC sheet states a range of 3-14V so that shouldn't have damaged it. (I hope)
I'm going to try and source a 3.5mm jack to RCA cable to cannibalize.
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