TDA7492P bluetooth amp bridging and power supply question

Discussion in 'Power Electronics' started by SimpleJoe, Mar 23, 2016.

  1. SimpleJoe

    Thread Starter New Member

    Mar 22, 2016
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    A while back i set out to make a portable bluetooth speaker using a Tda7492p 2x40 watt amp Specifically this one:
    http://www.banggood.com/TDA7492P-50...ceiver-Digital-Amplifier-Board-p-1003047.html)

    I did some research on the chip itself and found that they only recommend 2x25 w continuous but i also noted that this was at 8 ohms impedance. the speaker i built uses typically 1 port running a 120 watt 4 ohm 3-way home theater speaker, with a second sometimes plugged in (should i earth this out or something when not in use?). many of these amps vary their outputs with different impedances i just don't know if 4 ohms is the best as bangood recommends 8 but cannot see this anywhere on the spec sheet.

    there was also some notable distortion in the bass when in high gain mode which i can only think of the input voltage that could cause this (or once again the impedance of the speaker). it currently runs a 4 cell li-ion (~16.4v) but i have been planning to upgrade to 5 or 6 cell (20.5~24.6) (is this worth it).

    So just to summarise everything:
    1. should i some how increase theimpedance of the speakers (and easy way to do this would be great)
    2. should i increase the input voltage to the chip
    3. is there any way to bridge the outputs when the second is not in use or should i be doing something else with the connector
    Thanks,
    SimpleJoe
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,980
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    Its a Bridged output, so no you can't ground the outputs, you need to use both channels with 8ohms speakers.

    Do it right, or blow it up!
     
  3. SimpleJoe

    Thread Starter New Member

    Mar 22, 2016
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    0
    So both speakers have to be connected at the same time? I thought bridged outputs were only a single pair of outputs, not a pair of pairs (R+/- and L+/-) like how the amp is setup.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Yes, why would you want to build a stereo amplifier and have one speaker on it!!
     
  5. SimpleJoe

    Thread Starter New Member

    Mar 22, 2016
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    0
    That is why i asked if there was anyway to bridge the two outputs so instead of the current setup of 1 speaker only playing one side of a stereo output i could still use the one speaker but with a more powerful mono output
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,980
    744
    Then use a mono amplifier, or use one channel and put a 8ohms resistor as a dummy speaker on the dead channel.
     
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