riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

amplifier for rasberry pi B+ V1.2

Wed Dec 28, 2016 10:06 am

made electronic sound instrument using the rasberry pi B+ V 1.2. I connected Future Kit 2 W amplifier to the phones jack and it worked fine for a while.

now i have been trying to fix it , this combination does not work anymore, the sound does not come on. The rasberry seems to work fine, the lights come on when i connect it to the mains with the cord. I changed new Future Kit amp, the same kind but the new one does not work either.

can anyone tell me what kind of amplifier would work best to be connected with the output phones jack of the rasberry pi?
.....it's just a great instrument when it works!

riversun thanks

alphanumeric
Posts: 1533
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: amplifier for rasberry pi B+ V1.2

Fri Dec 30, 2016 9:41 pm

I'd plug a set of headphones in and make sure the jack is still outputting audio first.

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Sun Jan 08, 2017 8:58 am

thanks! i will do that!


riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Sun Jan 08, 2017 1:53 pm

alphanumeric wrote:I'd plug a set of headphones in and make sure the jack is still outputting audio first.
yes the audio works fine when i place headphones to the raspberry pi jack, after short loading period sounds good. but when i change there input going to the 2W future kit amplifier to the jack no more sound. this kind of 2W amp has been very good in other projects.....now i just don't know what does the rasberry would like to have as an amplifier.....

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Sun Jan 08, 2017 2:04 pm

The raspberry pi sound works fine when i place headphones to the output phones jack, that's why it seems like unnecessary to change the setting (also it's beyond my know-how with this tool)......the problem is i think to find an amplifier that would works with the raspberry pi and play the instrument sound through its speakers. Could the problem be that 2W is too low power for the job? what would be better?

alphanumeric
Posts: 1533
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: amplifier for rasberry pi B+ V1.2

Sun Jan 08, 2017 2:06 pm

Does that amplifier work if you plug it into another device, like a PC or MP3 player?

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Mon Jan 09, 2017 9:32 am

alphanumeric wrote:Does that amplifier work if you plug it into another device, like a PC or MP3 player?
yes. when i replaced the 2 W amplifier for the first time i tried it with cd-player and there it worked fine....there i got the thought that there is something in this two machines that stops them working together. Although when i replaced new future kit 2 W amp to the Raspberry output jack it worked fine maybe 10 times and now stops working again completely...

alphanumeric
Posts: 1533
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: amplifier for rasberry pi B+ V1.2

Mon Jan 09, 2017 10:41 am

I can't think of a reason why that would happen? If there is no mechanical fault the audio source must be switching to HDMI on the Pi or something?

User avatar
Burngate
Posts: 5403
Joined: Thu Sep 29, 2011 4:34 pm
Location: Berkshire UK
Contact: Website

Re: amplifier for rasberry pi B+ V1.2

Mon Jan 09, 2017 6:45 pm

The Pi doesn't care what gets plugged into its A-V socket - it doesn't sense it, it just outputs the audio (and the video) at a more-or-less standard level, on the assumption that something can use it, be that a pair of ear-buds, a small or large amplifier, or the whole of the PA system at Reading.

Similarly, the amplifier doesn't care what's plugged into it - anything injected into its input will come out of its output, as long as it's somewhere in the audio band.

Your system worked to begin with, so you're not too far wrong.
You say, in your third post, you tried a new amp, and that also worked for a short while before stopping.
The amp (both of them?) still works with another source, so you haven't properly broken it, and the Pi still puts out audio through headphones, so that's alright.

Which "Future Kit 2W amplifier" are you using? - they seem to make more than one, with varying amounts of data on them.
About the only thing wrong with them is the polarised capacitor on the input, which shouldn't cause problems, though I'd put a non-polarised one there, myself.

And how are you powering it?

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Tue Jan 10, 2017 9:08 am

http://future.makewebeasy.com/en/product/25383/fk602

it is this one. in the place of a battery i plug it into the wall with 2A/ 9V cord.

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Tue Jan 10, 2017 9:17 am

alphanumeric wrote:I can't think of a reason why that would happen? If there is no mechanical fault the audio source must be switching to HDMI on the Pi or something?
in the amplifier i have a speaker that is bigger than 0.25Watt.....i wonder if this is causing the problem.....the instruction sheet shows 0.25 Watt speaker used for this kind of amplifier

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Tue Jan 10, 2017 2:33 pm

inside of the instrument.JPG
inside of the instrument.JPG (54.61 KiB) Viewed 2426 times
Burngate wrote:The Pi doesn't care what gets plugged into its A-V socket - it doesn't sense it, it just outputs the audio (and the video) at a more-or-less standard level, on the assumption that something can use it, be that a pair of ear-buds, a small or large amplifier, or the whole of the PA system at Reading.

Similarly, the amplifier doesn't care what's plugged into it - anything injected into its input will come out of its output, as long as it's somewhere in the audio band.

Your system worked to begin with, so you're not too far wrong.
You say, in your third post, you tried a new amp, and that also worked for a short while before stopping.
The amp (both of them?) still works with another source, so you haven't properly broken it, and the Pi still puts out audio through headphones, so that's alright.



Which "Future Kit 2W amplifier" are you using? - they seem to make more than one, with varying amounts of data on them.
About the only thing wrong with them is the polarised capacitor on the input, which shouldn't cause problems, though I'd put a non-polarised one there, myself.

And how are you powering it?
amplifier is actually powered by 12V/ 2A cord.

User avatar
Burngate
Posts: 5403
Joined: Thu Sep 29, 2011 4:34 pm
Location: Berkshire UK
Contact: Website

Re: amplifier for rasberry pi B+ V1.2

Tue Jan 10, 2017 5:15 pm

Future Kit don't provide enough information - though more than many places do.
Still, from what I can see, it's a mono amplifier, with one input and ground.
Earphones are generally stereo, with two inputs and ground, and the Pi gives out stereo, again two outputs and ground.

It's not easy to see from your photo, but could it be that you haven't correctly mixed left and right into the amp?

The only pdf I could find said 2W, using a 12v supply and 8Ω speaker
Its figure of 0.25W is in their spec for current consumption - in other words, if you want 0.25W and you use an 8Ω speaker, it'll take 300mA

Having a speaker rated at greater than 2W won't be a problem. It just means you won't break the speaker even at full volume.

The impedence of the speaker is more important - They talk about 8Ω, but don't say whether 4Ω would be ok.
They also don't say what the chip is, so we can't go and look at its spec.
But if it couldn't handle a 4Ω load with a 12v supply, then the chip would die.
If the chip hasn't died with the speaker and supply you've got, then everything's hunky-dory.

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Tue Jan 10, 2017 7:05 pm

Burngate wrote:Future Kit don't provide enough information - though more than many places do.
Still, from what I can see, it's a mono amplifier, with one input and ground.
Earphones are generally stereo, with two inputs and ground, and the Pi gives out stereo, again two outputs and ground.

It's not easy to see from your photo, but could it be that you haven't correctly mixed left and right into the amp?

The only pdf I could find said 2W, using a 12v supply and 8Ω speaker
Its figure of 0.25W is in their spec for current consumption - in other words, if you want 0.25W and you use an 8Ω speaker, it'll take 300mA

Having a speaker rated at greater than 2W won't be a problem. It just means you won't break the speaker even at full volume.

The impedence of the speaker is more important - They talk about 8Ω, but don't say whether 4Ω would be ok.
They also don't say what the chip is, so we can't go and look at its spec.
But if it couldn't handle a 4Ω load with a 12v supply, then the chip would die.
If the chip hasn't died with the speaker and supply you've got, then everything's hunky-dory.
the speaker that i now have there should be 8ohm,it was measured ( but it's more than 0.25W quite a lot more...)
yes it is mono amplifier.....so how should i correctly mix left and right? that must be the problem!
or should i get stereo amplifier:
http://www.rtc-electronics.com.kw/Power ... eaker.html
would that be best to get my instrument working again and last? looks like then i need to get two speakers as well.....
my knowledge of electronics is very limited, but that stereo amp does not look harder to make......if you get stereo cable i guess it does not matter which wire goes to left and right as long as the ground part of the wire is correct?

User avatar
Burngate
Posts: 5403
Joined: Thu Sep 29, 2011 4:34 pm
Location: Berkshire UK
Contact: Website

Re: amplifier for rasberry pi B+ V1.2

Wed Jan 11, 2017 10:26 am

You're right, it doesn't matter which is left and which is right - unless you insist the first violins are on your left - as long as the ground is connected at both ends.

That RTC amplifier seems to be a Future Kit, and should be equally easy to construct.
It appears to use two TBA820M chips, so with that information you can find the datasheet, if you wish (http://www.fieros.de/philips/tba820m.pdf)

riversun
Posts: 10
Joined: Mon Aug 25, 2014 3:22 pm

Re: amplifier for rasberry pi B+ V1.2

Wed Jan 11, 2017 11:07 am

This is what i will do then! I am very grateful for your help!

Return to “Add-ons”

Who is online

Users browsing this forum: No registered users and 5 guests