Tpa6021a4n

Discussion in 'The Projects Forum' started by tracecom, Dec 22, 2011.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I am thinking about building a small stereo amplifier for my MP3 player using the TPA6021A4N (which I already have) based on the schematic in the attached data sheet. What do you think? What should I beware of?

    Thanks.
     
  2. jegues

    Well-Known Member

    Sep 13, 2010
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    Are you building it to learn? Or to use it?

    I think you would learn alot more designing your own amplifier from individual transistors.

    Have you learned about power amps?

    Then you could design it to meet any specific needs you have!
     
  3. crutschow

    Expert

    Mar 14, 2008
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    That chip should work fine if you just want a low power amp.

    Make sure you built it just as the schematic shows keeping all the components close to the chip, particularly the decoupling caps.

    Note that it may require a heat-sink of some sort to avoid over-temperature at high output volume.
     
  4. Audioguru

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    Dec 20, 2007
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    Can you find 4 ohm speakers? They are used in cars. If you use 8 ohm speakers then the output power is half and it will sound as loud as a cheap clock radio.

    The datasheet does not say where to buy a heatsink for the little DIL package.

    Maybe TI or another manufascturer makes a class-D stereo amplifier that does not get hot and it is in a DIL package that is big enough to solder the pins without using a microscope.
     
  5. tracecom

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    I have a pair of these speakers in decent enclosures.

    [​IMG]

    I don't know if this heat sink will be big enough; I suppose it's made to be epoxied on.

    [​IMG]
     
  6. Audioguru

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    The speakers appear to be tiny since they are rated at only 2W. Then they produce no bass sounds.

    The heatsink will be fine if you use a thin layer of epoxy cement.
     
  7. tracecom

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    Apr 16, 2010
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    I am considering whether to include a volume control in my build of this amplifier. If I don't include one in the amp, I would control the volume by means of the volume control on the MP3 player. In that case, should I just tie pin 18 (VOLUME) to Vcc, or should I use a voltage divider to run the amp at something less than wide open? (See page 15 of the datasheet.)

    If I decide to include a volume control, I plan to use a voltage divider to control pin 18. Should I make the range of the divider 100% of the range from ground to Vcc, or should I limit the range to something less, say 90%?

    Thanks.
     
  8. Audioguru

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    You probably need all the voltage gain you can get which is not much when the volume control voltage is 3V or more.

    The internal volume control is not smooth, IT STEPs in 32 steps (jerk, jerk, jerk). Use the smooth volume control on the MP3 player.

    The volume control pin should be filtered. Use a 1k resistor from the 5V supply to pin 18 and a 100uf capacitor to ground at pin 18.
     
    tracecom likes this.
  9. tracecom

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    Apr 16, 2010
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    Attached is my attempt at a schematic of the circuit. I plan to power it with a USB automobile cell phone charger. I realize the bypass and filter caps need to be close to the appropriate pins on the IC, but other than that, are there any errors that anyone sees?

    Thanks.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Looks like you have the Lout- and Rout- connected together. I wouldn't do that; you'll be shorting the low side of the amps together. Not only will that cut your output power in half, your amplifier IC will get very hot, very quickly.

    Go fish.
     
  11. tracecom

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    Apr 16, 2010
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    OK, I can separate those and use separate two-conductor jacks for the right and left speakers.

    I don't know what that means.

    Thanks for looking it over.
     
  12. Audioguru

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    Each speaker is driven by two amplifiers. One amplifier drives one speaker wire and the other amplifier drives the other speaker wire so that the voltage swing across the speaker is doubled then the power in the speaker is 4 times as much as when it is driven by only one amplifier. Also, the speaker does not need a huge coupling capacitor.

    The inputs are each driven by one signal wire and one ground wire.

    Make it like this:
     
  13. tracecom

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    I believe that I have made the changes suggested by SgtWookie and Audioguru and they are reflected in the attached schematic. Thanks for your help.

    As I posted in another thread, I am not sure if a car cell charger will provide enough power for this amp. The standard rating for such chargers seems to be 600mA and the app note for the IC says it could draw up to 2A. I don't plan on running it wide open, but I want to be able to hear it in my somewhat noisy truck.
     
  14. Audioguru

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    The low power amplifier (1.5W per channel) does not produce enough output power for a noisy truck unless you wear the speakers like headphones. A cheap ordinary car radio produces 14W per channel.

    2A at 5V is 10W. The total output from the amplifier is 3W and the total heating of the IC is 2.6W. Then the total power is (3 + 2.6)= 5.6W and the max current from the 5V power supply is (5.6/5)= 1.12A.
     
  15. JonDrBrown

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    Sep 10, 2015
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    The data sheet states that the amp works at maximum efficiency into an 8ohm load. Look closely at the values of dc blocking capacitors since these impact low frequency performance. My current set up with 2 amplifiers starts cutting off at 400Hz, far too high!
     
  16. GopherT

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    Nov 23, 2012
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    That warning about the thread being 4 years old didn't mean anything?
     
  17. JonDrBrown

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    Sep 10, 2015
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    Not to me. I looked up the chip to see what experiences others have had with it, even four years ago!