Preamp for arduino?

I've tried LM386 circuit, but the problem is it's noise (High frequency noise, hiss or like that). Also tried 1. feedback connection from output to 8th pin. 2. Placing a capacitor between Vcc and Gnd.

But still the noise when there is no input. If an audio is plying, it is very clear.

So I want either fix the noise (When no audio is plying) or suggest me a better preamp with maximum gain.

I want to make a station announcement system for a bus from GPS input. (is there any problem when using arduino(atmega328) for plying louder audios?, Is it necessary to use dedicated audio processing ic?)

The LM386 isn't a preamp. It's a power amp* (for driving a speaker).

I assume you're driving a speaker from the Arduino's output, or from an audio shield?

What happens when you disconnect the amplifier's input from the Arduino? i.e. Is the noise coming from the amplifier or from the Arduino?

If the noise is from the amplifier, it's probably power supply noise. Try a battery temporarily (just for the amplifier, not the Arduino) and if the noise goes away, the noise is from the power supply.

If the noise is from the Arduino, it's probably a software problem (or it could be the Arduino's power supply).

...with maximum gain.

With ~5V peak-to-peak out of the Arduino, you shouldn't need much voltage gain... If you're running the amplifier off of 5V you don't need voltage gain at all... The LM386's default gain of 20 is too much without a volume control. You only need current & power gain. And of course, the noise gets amplified along with the signal so the more gain you have the more noise you're going to hear (if the noise is coming out of the Arduino).

  • It's a low-power power amp, but anything that drives a speaker is a power amp. A preamp is used to amplify a microphone or phono-pickup (millivolts) to line level (about 1 Volt).

DVDdoug: The LM386 isn't a preamp. It's a power amp* (for driving a speaker).

I assume you're driving a speaker from the Arduino's output, or from an audio shield?

What happens when you disconnect the amplifier's input from the Arduino? i.e. Is the noise coming from the amplifier or from the Arduino?

If the noise is from the amplifier, it's probably power supply noise. Try a battery temporarily (just for the amplifier, not the Arduino) and if the noise goes away, the noise is from the power supply.

If the noise is from the Arduino, it's probably a software problem (or it could be the Arduino's power supply).

With ~5V peak-to-peak out of the Arduino, you shouldn't need much voltage gain... If you're running the amplifier off of 5V you don't need voltage gain at all... The LM386's default gain of 20 is too much without a volume control. You only need current & power gain. And of course, the noise gets amplified along with the signal so the more gain you have the more noise you're going to hear (if the noise is coming out of the Arduino).

  • It's a low-power power amp, but anything that drives a speaker is a power amp. A preamp is used to amplify a microphone or phono-pickup (millivolts) to line level (about 1 Volt).

The noise is not from arduino, because it sounds without connecting input. I'm using a 40W amplifier (12V), but the sound now getting is not enough for me. Because I want that to announce in a bus(with 4 speakers). So how can I get that much sound??

How are you connected, and what can you tell us about the 40W amp?

Were you using the LM386 in-between the Arduino and the 40W amp? That shouldn't be necessary.

A normal audio power amplifier works with a [u]line level[/u] input, so the Arduino should have no trouble driving it to full power.

Does the amp get loud enough with something else like a CD/DVD player or a computer?

If you're sure the amplifier is working, try a little test sketch with the [u]tone()[/u] function at about 1kHz. If that doesn't blast your ears out (with the amp's volume turned-up) you've got something wired wrong or some other hardware problem.

40W amp have 2 channels with left and right audio input. It also have volume, bass, treble controls. I've bought the circuit from a store and they told me that it may used to setup home theaters. So they are enough for me.

I've tried both: directly connecting arduino to amp and with the 386, and observed the sound is almost same.

The amp is extremely louder with an input from my phone headset pin. I'm very happy with that much sound.

So I think some kind of preamp is necessary in between arduino and 40w amp (like a transistor biasing), could you please suggest me that kind of circuit. Is there any signal amplifier (amplitude not power)? I think it may fix my problem. Thank you.