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Old 2nd April 2013, 10:11 PM   #1
JZatopa is offline JZatopa  United States
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Default Sure Electronics TPA3122 amp power supply

So i just put together a sure electronics TPA3122 amplifier the other day. I have found that if you power up the amp to fast it goes into some sort of protection where it just clicks. If you build this amp and are having the same problem, try turning it off and on again or finding a way to apply power to it a bit slower (seems to be more of a problem when you use a higher V to power the board).

Other then that the amp is working fine but I'm not sure what I should be using as a power supply and what voltage I should run it at for the best sound.

When I power the amp up and I connect my oscope to the power and ground I can see that my power rails are directly being affected by the audio source. I also see what looks like switching noise when no audio is playing. Is this normal?

So far I have tried a 12V smps wallwart, a 29V regulated linear supply and a meanwell 24V smps (lots of clicking problems). I am seeing this on all the supplies. Should I be concerned on how modulation of the power supply lines will affect the sound of the amp or is this normal? I have only built class a amplifiers up to this point so I am not use to seeing this from an amp.
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Old 2nd April 2013, 10:38 PM   #2
xrk971 is offline xrk971  United States
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That's a neat kit for $12. These are pretty good basic amps, make sure you don't have a cold solder joint on the shutdown pin 2 from the chip. It should not be left floating and a cold solder joint may cause an intermittent float - normal operation this pin is connected to positive supply thru a pull-up resistor to keep the logic high (>2volts). There is also possibility that caps at 220 uF are not big enough and try swapping out with say 470 uF might do the trick (main power caps not output stage caps). I doubt the problem is the caps as the datasheet specs 220 uF. The other problem could be an intermittent cold solder bridge from the mute pin 3 to pin 2. Applying high logic to pin 3 will mute output. Use a loupe and continuity tester to check your connections. Good luck. All it takes is one flaky solder bridge and the whole amp stops working.
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Old 3rd April 2013, 12:39 AM   #3
JZatopa is offline JZatopa  United States
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I think I have the clicking fixed.

Could someone tell me if this is normal?

sure electronics TPA3122 - YouTube

the amp sounds ok but I don't like the way it is modulating the power line.
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Old 3rd April 2013, 11:19 AM   #4
xrk971 is offline xrk971  United States
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So what was cause of clicking?
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Old 5th April 2013, 12:42 AM   #5
JZatopa is offline JZatopa  United States
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The board was going into a protection mode, I'm not the first with the problem it turns out.

Any idea if what is going on with the PS lines is normal?
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Old 5th April 2013, 01:25 AM   #6
xrk971 is offline xrk971  United States
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I don't know what the scale of the oscope trace is? What is the depth of modulation in percent of supply voltage, where are you measuring it at, and what is the amps rating of your power supply? Class D amps switch the power supply rail fully on and off to effect the pulse width modulation to make the audio. If your power supply is not big enough to handle the current draw when switched the modulation will show up. You might try increasing capacitor size on supply rails and see if things improve.

One reason why the amp may be going into protection mode is if you are overdriving it into a very low impedance load like less than 4 ohms and the amp overheats. This will also cause power supply rails to modulate. How many volts are you driving into speakers and what is supply voltage?
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Old 5th April 2013, 01:33 AM   #7
JZatopa is offline JZatopa  United States
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Quote:
Originally Posted by xrk971 View Post
I don't know what the scale of the oscope trace is? What is the depth of modulation in percent of supply voltage, where are you measuring it at, and what is the amps rating of your power supply? Class D amps switch the power supply rail fully on and off to effect the pulse width modulation to make the audio. If your power supply is not big enough to handle the current draw when switched the modulation will show up. You might try increasing capacitor size on supply rails and see if things improve.

One reason why the amp may be going into protection mode is if you are overdriving it into a very low impedance load like less than 4 ohms and the amp overheats. This will also cause power supply rails to modulate. How many volts are you driving into speakers and what is supply voltage?
Of course I don't remember the scale if I were to guess .1V/div. measured right at the power input terminals to the amp board. The PS was a spare transformer I had from an old receiver + CRC using 2 3300uF caps I had laying around.

The amp was connected to 8 ohm speakers. The problem presented itself from the second the amp was turned on without input. It happened with a 24V smps and the 30V linear I threw together. If you turn the amp off and on the problem goes away.
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Old 5th April 2013, 04:08 AM   #8
prezden is offline prezden  Canada
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I'm running one with a 24V meanwell with no problems at all.
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Old 2nd April 2014, 11:03 PM   #9
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Hey guys, picked up this old thread because i don`t want to open a new one..

I also build the TDA3122 from Sure-Amps. I finished the board and tested it with a small 6,8V 2A powersupply and it worked without problems. I also brought a DC Protection and Rectifier kit (35v 8x2200uF). My (bit oversized..) transformer is a 160VA 2x15v and i use the second secondary coil for the DC protection and status lamp at the front. The amp itself, the dc protection and the power supply worked without problems if i test them just connected to the power supply alone. So i started completing the amp and finally it doesn`t work.
When i turn it on, sometimes the dc protection does not went into protection mode but then theres coming a fast (3-4 klicks a second..) ticking noice out of the speakers and wen i turn the amp on and of it went into protection mode. Also the green LED on the PSU board is not glowing.

Do you have any idea what i did wrong? - Is there a typical mistake or problem with this amp?


Sorry for my bad english!
Greetings from germany
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Old 3rd April 2014, 08:50 AM   #10
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I removed the amp board and tested it again with the 6,8V power supply and
i got 3,4V DC on the speaker output . I can`t unterstand what i did wrong, i have constant 22V DC power output, the speaker protection works fine (thats was really god for my speakers.. ) and the amp board was also working good untill i put everything together..
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