How to drive an external amplifer from a arduino

Hello.

I'm using the super mario sketch using digitalwrite to out put the song.

I want to output this to a external boom box. It is working but I have to turn the volume up all the way to heard the song. It should be blasting it out when the volume is all the way up.

I'm wondering if there is some pre-amp I can build to be able increase the input signal to the boom box.

I tried a sample project using tone() and it had the same results.

I don't want to build the amp - I found lots of example of this. I want to increase the volume on the external boom box.

Any help here would be great.

Code, circuitry, wiring diagram..... Else You can search for the answer in the stars.

Image

/*
Arduino Mario Bros Tunes
With Piezo Buzzer and PWM

Connect the positive side of the Buzzer to pin 3,
then the negative side to a 1k ohm resistor. Connect
the other side of the 1 k ohm resistor to
ground(GND) pin on the Arduino.

by: Dipto Pratyaksa
last updated: 31/3/13
*/

/*************************************************

  • Public Constants
    *************************************************/

#define NOTE_B0 31
#define NOTE_C1 33
#define NOTE_CS1 35
#define NOTE_D1 37
#define NOTE_DS1 39
#define NOTE_E1 41
#define NOTE_F1 44
#define NOTE_FS1 46
#define NOTE_G1 49
#define NOTE_GS1 52
#define NOTE_A1 55
#define NOTE_AS1 58
#define NOTE_B1 62
#define NOTE_C2 65
#define NOTE_CS2 69
#define NOTE_D2 73
#define NOTE_DS2 78
#define NOTE_E2 82
#define NOTE_F2 87
#define NOTE_FS2 93
#define NOTE_G2 98
#define NOTE_GS2 104
#define NOTE_A2 110
#define NOTE_AS2 117
#define NOTE_B2 123
#define NOTE_C3 131
#define NOTE_CS3 139
#define NOTE_D3 147
#define NOTE_DS3 156
#define NOTE_E3 165
#define NOTE_F3 175
#define NOTE_FS3 185
#define NOTE_G3 196
#define NOTE_GS3 208
#define NOTE_A3 220
#define NOTE_AS3 233
#define NOTE_B3 247
#define NOTE_C4 262
#define NOTE_CS4 277
#define NOTE_D4 294
#define NOTE_DS4 311
#define NOTE_E4 330
#define NOTE_F4 349
#define NOTE_FS4 370
#define NOTE_G4 392
#define NOTE_GS4 415
#define NOTE_A4 440
#define NOTE_AS4 466
#define NOTE_B4 494
#define NOTE_C5 523
#define NOTE_CS5 554
#define NOTE_D5 587
#define NOTE_DS5 622
#define NOTE_E5 659
#define NOTE_F5 698
#define NOTE_FS5 740
#define NOTE_G5 784
#define NOTE_GS5 831
#define NOTE_A5 880
#define NOTE_AS5 932
#define NOTE_B5 988
#define NOTE_C6 1047
#define NOTE_CS6 1109
#define NOTE_D6 1175
#define NOTE_DS6 1245
#define NOTE_E6 1319
#define NOTE_F6 1397
#define NOTE_FS6 1480
#define NOTE_G6 1568
#define NOTE_GS6 1661
#define NOTE_A6 1760
#define NOTE_AS6 1865
#define NOTE_B6 1976
#define NOTE_C7 2093
#define NOTE_CS7 2217
#define NOTE_D7 2349
#define NOTE_DS7 2489
#define NOTE_E7 2637
#define NOTE_F7 2794
#define NOTE_FS7 2960
#define NOTE_G7 3136
#define NOTE_GS7 3322
#define NOTE_A7 3520
#define NOTE_AS7 3729
#define NOTE_B7 3951
#define NOTE_C8 4186
#define NOTE_CS8 4435
#define NOTE_D8 4699
#define NOTE_DS8 4978

#define melodyPin 3
//Mario main theme melody
int melody = {
NOTE_E7, NOTE_E7, 0, NOTE_E7,
0, NOTE_C7, NOTE_E7, 0,
NOTE_G7, 0, 0, 0,
NOTE_G6, 0, 0, 0,

NOTE_C7, 0, 0, NOTE_G6,
0, 0, NOTE_E6, 0,
0, NOTE_A6, 0, NOTE_B6,
0, NOTE_AS6, NOTE_A6, 0,

NOTE_G6, NOTE_E7, NOTE_G7,
NOTE_A7, 0, NOTE_F7, NOTE_G7,
0, NOTE_E7, 0, NOTE_C7,
NOTE_D7, NOTE_B6, 0, 0,

NOTE_C7, 0, 0, NOTE_G6,
0, 0, NOTE_E6, 0,
0, NOTE_A6, 0, NOTE_B6,
0, NOTE_AS6, NOTE_A6, 0,

NOTE_G6, NOTE_E7, NOTE_G7,
NOTE_A7, 0, NOTE_F7, NOTE_G7,
0, NOTE_E7, 0, NOTE_C7,
NOTE_D7, NOTE_B6, 0, 0
};
//Mario main them tempo
int tempo = {
12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,

12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,

9, 9, 9,
12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,

12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,

9, 9, 9,
12, 12, 12, 12,
12, 12, 12, 12,
12, 12, 12, 12,
};
//Underworld melody
int underworld_melody = {
NOTE_C4, NOTE_C5, NOTE_A3, NOTE_A4,
NOTE_AS3, NOTE_AS4, 0,
0,
NOTE_C4, NOTE_C5, NOTE_A3, NOTE_A4,
NOTE_AS3, NOTE_AS4, 0,
0,
NOTE_F3, NOTE_F4, NOTE_D3, NOTE_D4,
NOTE_DS3, NOTE_DS4, 0,
0,
NOTE_F3, NOTE_F4, NOTE_D3, NOTE_D4,
NOTE_DS3, NOTE_DS4, 0,
0, NOTE_DS4, NOTE_CS4, NOTE_D4,
NOTE_CS4, NOTE_DS4,
NOTE_DS4, NOTE_GS3,
NOTE_G3, NOTE_CS4,
NOTE_C4, NOTE_FS4, NOTE_F4, NOTE_E3, NOTE_AS4, NOTE_A4,
NOTE_GS4, NOTE_DS4, NOTE_B3,
NOTE_AS3, NOTE_A3, NOTE_GS3,
0, 0, 0
};
//Underwolrd tempo
int underworld_tempo = {
12, 12, 12, 12,
12, 12, 6,
3,
12, 12, 12, 12,
12, 12, 6,
3,
12, 12, 12, 12,
12, 12, 6,
3,
12, 12, 12, 12,
12, 12, 6,
6, 18, 18, 18,
6, 6,
6, 6,
6, 6,
18, 18, 18, 18, 18, 18,
10, 10, 10,
10, 10, 10,
3, 3, 3
};

void setup(void)
{
pinMode(3, OUTPUT);//buzzer
pinMode(13, OUTPUT);//led indicator when singing a note

}
void loop()
{
//sing the tunes
sing(1);
sing(1);
sing(2);
}
int song = 0;

void sing(int s) {
// iterate over the notes of the melody:
song = s;
if (song == 2) {
Serial.println(" ‘Underworld Theme’");
int size = sizeof(underworld_melody) / sizeof(int);
for (int thisNote = 0; thisNote < size; thisNote++) {

// to calculate the note duration, take one second
// divided by the note type.
//e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
int noteDuration = 1000 / underworld_tempo[thisNote];

buzz(melodyPin, underworld_melody[thisNote], noteDuration);

// to distinguish the notes, set a minimum time between them.
// the note’s duration + 30% seems to work well:
int pauseBetweenNotes = noteDuration * 1.30;
delay(pauseBetweenNotes);

// stop the tone playing:
buzz(melodyPin, 0, noteDuration);

}

} else {

Serial.println(" ‘Mario Theme’");
int size = sizeof(melody) / sizeof(int);
for (int thisNote = 0; thisNote < size; thisNote++) {

// to calculate the note duration, take one second
// divided by the note type.
//e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
int noteDuration = 1000 / tempo[thisNote];

buzz(melodyPin, melody[thisNote], noteDuration);

// to distinguish the notes, set a minimum time between them.
// the note’s duration + 30% seems to work well:
int pauseBetweenNotes = noteDuration * 1.30;
delay(pauseBetweenNotes);

// stop the tone playing:
buzz(melodyPin, 0, noteDuration);

}
}
}

void buzz(int targetPin, long frequency, long length) {
digitalWrite(13, HIGH);
long delayValue = 1000000 / frequency / 2; // calculate the delay value between transitions
//// 1 second’s worth of microseconds, divided by the frequency, then split in half since
//// there are two phases to each cycle
long numCycles = frequency * length / 1000; // calculate the number of cycles for proper timing
//// multiply frequency, which is really cycles per second, by the number of seconds to
//// get the total number of cycles to produce
for (long i = 0; i < numCycles; i++) { // for the calculated length of time…
digitalWrite(targetPin, HIGH); // write the buzzer pin high to push out the diaphram
delayMicroseconds(delayValue); // wait for the calculated delay value
digitalWrite(targetPin, LOW); // write the buzzer pin low to pull back the diaphram
delayMicroseconds(delayValue); // wait again or the calculated delay value
}
digitalWrite(13, LOW);

}
SCHEMATICS

I want to output this to a external boom box. It is working but I have to turn the volume up all the way to heard the song. It should be blasting it out when the volume is all the way up.

It should be plenty-loud! Maybe your connector is wired wrong or maybe there's something wrong with the boom-box.

The Arduino's digital output is either zero or +5V (5V peak-to-peak). The consumer [u]audio line level[/u]* (the RCA audio outputs from a CD/DVD player or TV, etc.) is about 1V peak-to-peak so the Arduino makes a "hot" like-level signal.

You should put a capacitor in series with the Arduino output to block the DC (then the voltage will go positive and negative (like a normal audio signal) from -2.5V to +2.5V. But, most likely that's not the problem (and the boom box may have a capacitor on it's input).

And, you should wire the left & right connections together so you can get sound from both channels.** (If you're hearing sound from both speakers and you didn't intentionally connect them together, you may have connected between the left & right channels instead of making a ground connection.)

  • It's not a tightly-controlled spec, and with normal audio some songs/programs are louder than others and sometimes there is a volume control, etc. But usually line-outputs are a little "hot" and usually line-inputs are a little extra-sensitive so there's usually no problem getting full-volume or even driving the amplifier into distortion when the volume is turned-up.

** It's OK to "short" the left & right inputs together but you should never short outputs together.

Thanks for this. I only have one channel connected and the ground. Will wire the left and right together and try it. barely hear the output with the volume turned up all the way. I've tried it on two different audio devices so far.

Assuming the output is going 0-5V and not -2.5 to +2.5 since I'm using digitalWrite?

What size cap do you suggest?

Thanks!

r570sv.

I'm still guessing you're wired wrong. Try the same plug & wires "adapted" to another audio source.

What size cap do you suggest?

About 1uF. (With the +end toward the Arduino... 1uF or higher capacitors are usually polarized electrolytics.)

DC is zero-Hz and you are making a [u]high pass filter[/u] to block the DC. If we assume a typical line-input resistance/impedance of 10K to 100K, 1uF allows bass below 20Hz to pass-through.

A higher value capacitor would work too.

A 0.1uF capacitor would probably work because it doesn't look like you are using low frequencies, plus the input impedance may be higher.

since I'm using digitalWrite?

The regular Arduino doesn't have a true analog output so it's ALWAYS zero or 5V. analogWrite() is 0-5V [u]PWM[/u] which can "approximate" analog to control the speed of a motor or make an LED appear dim.

IT WORKED!

THANKS!

I did have it wired correctly BTW.

Thanks for the assist here!

R570sv.