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Class D Switching Power Amplifiers and Power D/A conversion

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Old 14th April 2009, 06:03 AM   #1
SMD29 is offline SMD29  United States
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Default UAM2 amp or better?

Has anyone had experience with this amp kit or know of something better. I tried using a 20 watt bridge amp from Cana Kit

http://www.electronickits.com/kit/complete/ampl/CANUK193.htm

the loudness is good however it just got way to much noise. What I am wanting is once I flip the power switch , the unit is quiet until I push the button trigger to hear the audio via Mp3 player. The unit as it is now makes no noise once powered up until I push the button but it is not loud enough, I add this amp and turn it on, and get alot of noise before the audio tracks are heard.

thought perhaps this D class amp might be a better bet? Any suggestions or feedback

Scott
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Old 14th April 2009, 06:10 PM   #2
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Scott, that doesn't look like the most spohisticated amp on the planet, so you can probably do bettr with one of the available class D boards or kits.

Search these forums and you'll find lotf of discussions, but you are mainly looking for Tripath 2020 and 2024 (and also 2021b). The former is about 7 clean watts into 8 ohms, the others are a little more powerful. Also check out the kits, especially the Amp6 at 41hz.com. Highly recommended. Other assembled Tripath boards are on eBay.

Quote:
The unit as it is now makes no noise once powered up until I push the button but it is not loud enough, I add this amp and turn it on, and get alot of noise before the audio tracks are heard.
Not sure what to make of this. Are you just saying it's noisy? Is there something in between the MP3 player and your kit amp?

--Buckapound
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Old 14th April 2009, 07:30 PM   #3
SMD29 is offline SMD29  United States
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Default UAM2 :Reply

Thank you I will look into those. Cost is a factor, to have the amp kit or assembled amplifier under 50.00 is key.

What I meant by noise, is when I turn on the power, there is this static "white noise" sound. I assume it is coming from the amp, as there is none of that when it is just the mp3 player. Not sure if some kind of filter can be added or what.

The mp3 player only gives 3watts per channel or 6watt mono, the amp boosts it to around 20 watts. I have to keep the it under between 20-30watt amp any higher requires more power which means larger battery packs.

Hope this gives you a better picture

Scott
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Old 14th April 2009, 07:49 PM   #4
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It's a very bad idea to use the output of a 3w amplifier as the input to another amplifier, as it just doesn't work like that. That may explain the noise you're getting, and is bound to create some distortion as well. Not good.

What you need is a line level output, or a headphone output should also work. The MP3 player should have that somewhere. Try that first. If you have to go through the speaker outputs, you will need a resistor (one per channel) to knock the speaker-level signal down to something usable for the amp. Maybe somewhere around a few hundred K ohms?

Let us know what happens.

FYI, you will get much more power and battery life from a class D amplifier than you will from the kit you're using, as they are much more efficient.

--Buckapound
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Old 15th April 2009, 07:06 PM   #5
SMD29 is offline SMD29  United States
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Default Line Out

That is what I did, the Mp3 player drives the speakers at 3watts per channel. I used the line out jack 3.5mm hooked it up to the 20 watt amp. Powered it up and get that white noise sound. My concern with amps with the heatsink is how hot they will get. Which is why D class appeals to me.

Last night I tried my first surface mount soldering and ended up botching the board I think. That was for the UAM2, I have not found a 20 watt D class amp that is pre-assembled yet.
That is key as this is small run commercial unit.

I did see the T-amp 10 for 99.00, which looked interesting but not sure what the size is. The size of the amp is a big factor as I only have a few inches by a few inches of space for this to go.


Scott
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Old 15th April 2009, 07:29 PM   #6
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Quote:
Mp3 player drives the speakers at 3watts per channel. I used the line out jack 3.5mm hooked it up to the 20 watt amp
This really makes no sense. The output is either a line level jack or it's 3 WPC, but it can't be both. Might be worth checking the specs again, because something's not right here.

As for the small amp boards, you aren't looking very hard:

http://cgi.ebay.com/New-Version-Trip...QQcmdZViewItem[QUOTE]Mp3 player drives the speakers at 3watts per channel. I used the line out jack 3.5mm hooked it up to the 20 watt amp

--Buckapound.
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Old 15th April 2009, 07:32 PM   #7
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Sorry, garbled the URL trying to get the quote thing working:

http://cgi.ebay.com/New-Version-Trip...QQcmdZViewItem
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Old 15th April 2009, 11:54 PM   #8
SMD29 is offline SMD29  United States
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Default Mp3

The mp3 player was hooked to my battery pack, the speakers connecting to the Mp3 player, the max amount was 6w thats what the Mp3 player could do. It was not enough. That is why I am looking into an amp, yes the line out jack is on the mp3 and that then goes to the amp.

I saw the some of the ebay varieties but need an amp that I can order more than 1 or 2 or even 7 of them. Some of the amps on ebay only had limited amps available.

I will keep looking, the D or T class amps seem like the best way to go. As long as it can deliver 15, 20, even 25 watts and be powered on 12-18 Volts.

Scott
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Old 16th April 2009, 01:26 AM   #9
SMD29 is offline SMD29  United States
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Default T-Amp 10 and 20

I did see a T-AMP 20 board and heat sink... the only thing I can see that could be an issue is it recommends 12volts. My pack is 14.8 and the only down size in a battery pack is 11.1V.

But could be a good start
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Old 16th April 2009, 12:50 PM   #10
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I can assure you that those suppliers can supply you with as many amps as you want to buy. The one seller, Arjen, has been a frequent participant on these forums, so you might want to talk to him.

I know, lithium batteries are just a little off the range for these. You definitely want to steer to the 2020 or 2021b chips as they can handle a little more voltage. Still, I think 14.8 is a little high. But you can put a diode in series with the battery pack, and that will drop the voltage about a volt. A more sophisticated alternative would be to rig up a voltage regulator.

Also, you are still getting this wrong. Line output is not 6 watts!

--Buckapoound
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