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rPioneer
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Amplifier for 2W speaker in robot

Wed Jul 01, 2015 7:25 pm

I'm looking to use a single small 2W 20mm x 40mm rectanglular speaker (http://www.maplin.co.uk/p/2w-mylar-and- ... 40mm-n99fu) in a robot I'm building. I was wondering if someone could point me in the right direction for a amplifier to use- amplifying the audio jack output from the Pi to a reasonable level. I'm looking for something reasonably good quality, able to output speech (probably espeak) and recorded sounds from Sonic Pi, possibly also music though this is not the aim of the robot. I would like it to be as small as possible really as space is somewhat limited, and preferably less than £10.
I've found this:
http://www.ebay.co.uk/itm/Mini-PAM8403- ... 3f46c11d16
but as I have no experiance with amplifiers, I don't know if it would be a good choice.

Thank you very much, forumgoers!
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
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ame
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Re: Amplifier for 2W speaker in robot

Thu Jul 02, 2015 12:02 am

I have precisely that amplifier board, from DealExtreme in China. It is super-simple to use, and incredibly loud! You'll probably keep the volume quite low. I use it for OpenELEC with the Pi's 3.5mm audio output. Sounds great.

You don't need any extra parts, just solder wires for 5V supply (from a USB output is fine). Speakers. Audio input. Done.

However, you might prefer a mono amp, as you have a single speaker:
http://www.dx.com/p/jf0501-diy-0-5-3w-m ... ZR901L7J9M

Or you could hack one of these, it has an amp inside:
http://www.dx.com/p/hamburger-style-min ... ZR_FlL7J9M

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rPioneer
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Re: Amplifier for 2W speaker in robot

Thu Jul 09, 2015 9:41 am

Thank you for your interest. I bought the one I found, and it's working well. It does turn up loud! :D
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
.

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rPioneer
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Re: Amplifier for 2W speaker in robot

Thu Jul 30, 2015 11:35 pm

Hmm... It was nicely loud with a mp3 player, but on the Pi (ALSA volume turned right up) it was very quiet. :( Not as good as I expected.
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
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ame
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Re: Amplifier for 2W speaker in robot

Fri Jul 31, 2015 1:29 am

That's strange. I use mine with OpenELEC on the Pi. The amp is connected directly to the Pi 3.5mm output. The sound fills the room at about 2/3 volume. I usually turn it down lower than that.

metalj
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Re: Amplifier for 2W speaker in robot

Fri Jul 31, 2015 2:06 am

I saw a 100w mini portable pa with a rechargeable battery for $35 on amazon.
Backspace 28 times :)

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rPioneer
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Re: Amplifier for 2W speaker in robot

Sat Aug 01, 2015 11:26 pm

Powered from 5V? What speaker are you using? I just plugged mine into 9V *magic smoke* :(
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
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ame
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Re: Amplifier for 2W speaker in robot

Sat Aug 01, 2015 11:36 pm

Ah. The maximum supply voltage is 5V. I use a USB supply. I am also driving a pair of small bookshelf speakers. They sound great!

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rPioneer
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Re: Amplifier for 2W speaker in robot

Sat Aug 01, 2015 11:46 pm

Could it perhaps be something to do with the different operating systems? And what kind of lead are you using for the jack? A standard 3.5mm jack that you cut one end off and soldered to the amplifier?
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
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ame
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Re: Amplifier for 2W speaker in robot

Sat Aug 01, 2015 11:52 pm

It's unlikely to be the OS, but you could try different ones to see.

The audio cable I made myself. I soldered a 3.5mm stereo socket to the amp board via a short length of cable. Then I made an audio cable for the Pi with a right-angled 3.5mm stereo plug at each end.

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rPioneer
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Re: Amplifier for 2W speaker in robot

Sun Aug 02, 2015 12:05 am

That sounds similar to my setup. I hacked (off) a 3.5mm jack and soldered breadboard jumpers to GND and L+ (or whatever you want to call them) for the Pi side, and the speaker wires are soldered directly to the amp.
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
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ame
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Re: Amplifier for 2W speaker in robot

Sun Aug 02, 2015 12:30 am

If yours is inside your robot then that makes sense to keep the space requirements down.

I am installing mine in an Altoids tin to make a tiny amp for my home theatre. I used a strip of spring connectors at the back for the speakers. Power input is via a 2.1mm socket. Audio input is the 3.5mm jack. The volume control sticks through the front and has a black knob on it. Finally a green LED is connected to the switch and lights up when the amp is on.

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rPioneer
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Re: Amplifier for 2W speaker in robot

Sun Aug 02, 2015 12:49 am

That sounds really nice! :) I know this is a really silly question, but are you definite that the speakers you're using don't have amps in them? Obviously I don't know what your setup is like, and if you're plugging the speakers into the back of the amp the I would guess there's no other power going into the speakers... but still, you are definite?
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
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ame
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Re: Amplifier for 2W speaker in robot

Sun Aug 02, 2015 1:45 am

Definite. The speakers were, er, rescued from the trash. They are just speakers with no built-in amp. Two wires from the speaker outputs on the amp go to two terminals on the back of the speakers. No power supply is connected to the speakers.

You already know what your amp is capable of, using the MP3 player. Or rather, what it was capable of before you fried it.

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rPioneer
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Re: Amplifier for 2W speaker in robot

Tue Aug 04, 2015 3:27 pm

Well thank you for all your help, ame. I'll buy another amp and do some tests. Perhaps it's the size of the speakers, or my wires... What resistance are your speakers, and approximately what size?
Toxic yellow HDMIPi, Raspberry Pi B Revision 2 running Raspbian, Raspberry Pi A+ on a robot called Lobsang (anyone read The Long Earth?).
Happy to chat, but don't expect me to be an expert! Eager to learn from peers / gods / gurus / geeks
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