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Powering 8 x Kemo 12w Amplifier Modules?

Discussion in 'General Electronics Discussion' started by yep, Jul 26, 2013.

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  1. yep

    yep

    7
    0
    Jul 26, 2013
    Hi there,

    First post here! Was wondering if you could help...

    I'm working on a project that requires 8 x Kemo 12w amplifier modules, each boosting a signal (from a computer's audio interface) to a 8 ohm mini speaker cone. 8 audio signals > 8 amps > 8 speakers, basically a micro multi channel system.

    Kemo 12w Amplifier module: http://www.maplin.co.uk/12w-universal-amplifier-module-46809 [/URL]

    My question is about powering the things... I've been experimenting with one and it's all working good. The max current consumption of 1 Kemo amp is 800mA, could I run all 8 from a single 9v DC 2.2A supply like this: http://www.maplin.co.uk/ac-dc-fixed-voltage-switched-mode-power-supplies-48484

    Or is this the one i need: http://www.maplin.co.uk/12vdc-10a-power-supply-with-2.1mm-tip-513521

    Also, I'm experimenting with a Kemo 3w Stereo amplifier module and I'm getting some annoying buzz and interference (I'm not getting this at all from the Kemo 12w), I have it hooked up the way it suggests in the data sheet and have tried the suggested way to get rid of hum etc. Any suggestions to eliminate the unwanted noise?

    http://www.kemo-electronic.de/datasheets/m055.pdf

    Any help and advice would be incredible and sorry for the basic questions.

    Nice to meet you all!

    Cheers!
     
  2. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    I suggest you extract the relevant data from the data sheets. For instance, the amplifier has a maximum voltage supply of 10V.

    If you have eight amplifiers taking 800mA each, that makes 6.4A. A 2.2A supply may work if you keep the volume down or it may fry, why risk it?
     
  3. yep

    yep

    7
    0
    Jul 26, 2013
    Thanks a lot for the reply and advice. I'll go with a 12v 10A power supply to power 8 of the Kemo 12w.

    Thank again for you help.
     
  4. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    I could not get at the data sheets again. If I was right previously, the amplifiers want less than 10V. They may have a very short but happy life if run on 12V particularly if the supply is not stabilised and the output is high on low loads.
     
  5. yep

    yep

    7
    0
    Jul 26, 2013
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Hum comes from a number of sources:

    1) power supply
    2) input leads
    3) ground loop
    4) signal source
    5) directly injected into the circuit

    For noise, you can add

    6) internally generated.

    You should be able to eliminate these one by one.

    For example shorting the input very close to the amplifier removes (2) and (4)

    If a large capacitor placed across the supply rail doesn't have any effect at low volume levels, you have almost certainly eliminated (1).
     
  7. yep

    yep

    7
    0
    Jul 26, 2013
    That's great advice. Thanks. I'll try all these tonight.

    Just a question... and please excuse my lack of knowledge, what do you mean by "shorting the input very close to the amplifier"?

    Also, in the hook up diagram there are a couple of things I don't fully understand. In the diagram, arrows on the ground pot lugs indicates that they go to an external ground (I have them hooked up to the negative input of the amp)... what does this mean? Where do I also hook them up to? Also, in the diagram the input arrow appears to cross the ground lug on the pots... do these have to be connected?

    http://www.kemo-electronic.de/datasheets/m055.pdf

    Oh and the type of noise coming from the Kemo 3w is a faint but audible high pitched squeal (around 10-12khz). I've already tried putting a 1000uf cap across the power rails and no change in noise.

    Thanks again.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    That means connect both input terminals together. It might be by placing a short wire link across screw terminals, or making a plug that has the ground and signal connected together and plugging that in, or possibly even by actually soldering a wire across the input.

    Just make sure you only do this to the input. Doing it to outputs will cause the magic smoke to come out.

    The arrows indicate these wires go to your input. The one with the ground symbol on it is the one that should go to the ground of your input signal (if one side is grounded)

    That's not hum then...

    Is it in a car? Does the squeal stop when the car isn't running?

    Does it stop when you short the input?

    Is the amplifier "Class D" (or some later letter)?
     
  9. yep

    yep

    7
    0
    Jul 26, 2013
    It's not in a car... just using it on a table in the house.

    I tried shorting the input, as you suggested, but it doesn't stop the noise.

    I'm not sure if it's a Class D amp, I can't find any info in the documentation to say that it is or isn't. The closest thing I got was it's listing on the Farnell website has class d tags on it...

    Thanks.
     
  10. yep

    yep

    7
    0
    Jul 26, 2013
    Just another thing regarding the Kemo M055 stereo 3w amp. I came across another different hook up diagram. This one suggests a fuse between the + power. It has 7 leads but the amp only has 6? A bit confusing...

    Also, the arrow labeled 'L+R ground', is this connected to the negative of the power supply or somewhere else?

    Thanks.
     
  11. yep

    yep

    7
    0
    Jul 26, 2013
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