I salvaged a pair of speaker drivers from USB-powered computer speakers that is .75 Watts/8 ohm per channel (2 channels total, L/R). I want to be able to drive audio through it and have volume control. I know that a basic audio system requires:

  1. Signal source (For simplicity, I want my device to take the signal via AUX port)
  2. Power amplifier
  3. Speaker driver

With such a low RMS power rating, I'm tempted to connect the L/R channels from a source directly to the speakers but I'm not sure of the energy of the source signal.

Link to speakers I have: https://www.bestbuybusiness.com/bbfb/en/US/adirect/bestbuy?cmd=catProductDetail&showAddButton=true&productID=BB12339197


2 Answers 2


If the source has enough power, then it will work. If it doesn't, then it will need an amplifier.

Simplest is to have an amplifier anyway, then you don't care about the source.

  • \$\begingroup\$ Are there amplifiers for .75 Watt speakers? I've googled and found amplifiers that provider >1 Watt of power. I don't mean to start a discussion about what amplifiers to choose. I just need the knowledge to know which amplifiers can drive it. \$\endgroup\$
    – Minh Tran
    Commented Dec 30, 2014 at 19:42
  • \$\begingroup\$ You can use a more powerful amplifier than the speakers need. 1-2W is fine. You could even get away with a little below the speaker rating if you don't turn it up to max volume \$\endgroup\$
    – Majenko
    Commented Dec 30, 2014 at 19:44

Driving 8 ohms from a line out is not likely to succeed. You can use a 5 volt D class amplifier such as CP2212 / TPA2012. That would be pretty much perfect for the job.

I've used http://www.chiphomer.com/cp2212.htm, but there are a lot of D class amplifiers like this.

  • \$\begingroup\$ Interesting! I've never used or ordered an QFN-packaged device before. Looking at the datasheet (chiphomer.com/pdf/en_cp2212.pdf), What should Ci be? (Inputs to gain adjust) \$\endgroup\$
    – Minh Tran
    Commented Dec 30, 2014 at 20:03
  • \$\begingroup\$ Also, what is SDR/SDL and how can I adjust volume? By using gain select bits? \$\endgroup\$
    – Minh Tran
    Commented Dec 30, 2014 at 20:04
  • \$\begingroup\$ Those pins are Shutdown Left and Shutdown Right. And yes, controlling the gain bits gives you a kind of volume control, although it's really meant for adjusting the amplifier's operation to best match the speaker elements that are connected to it. You must adjust the volume by adjusting the input signal. \$\endgroup\$
    – PkP
    Commented Dec 30, 2014 at 20:27

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