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Bluetooth Audio Amplifier AUD $8.92, Battery Capacity Voltage Indicator AUD $10.19, Voltage to PWM Converter AUD $4.84 ICStation

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Digital Amplifier Wireless Bluetooth Audio Amp Board Headphone Dual Channel 50W+50W Power Amplifier Module with Protective Shell
$6.99, 35% off with extra $3 for tracking number service.
Find it from http://www.icstation.com/digital-amplifier-wireless-bluetoot…

0-5V/0-10V to 0-100% Voltage to PWM Converter Board Duty Cycle Adjustable Conversion Module
$3.79, 35% off with extra $3 for tracking number service.
Find it from http://www.icstation.com/voltage-converter-board-duty-cycle-…

New LY7 12V Lead Acid Battery Capacity Indicator Voltage Indicator LCD Display Battery Power Tester with Touch Button
$7.99, 25% off with extra $3 for tracking number service.
Double indicator from http://www.icstation.com/lead-acid-battery-capacity-indicato…

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ICStation, China
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  • Store name in title pls.

  • What's the amperage needed for the Bluetooth board?
    Assuming voltage is 12v

    • How loud do you want? 12V @ 1A will be OK, but not 50W.

      An old laptop power brick will give more volume / less clipping. Or run it from an 18V/20V powertool battery.
      These work well with a li-ion battery,

      Can't really answer as the shop does not even say what chip this amp uses. But I'd guess input voltage limits output voltage?

      • That's what I'd like to know, does the loudness limited by wattage?
        The minimum requirement for amperage

    • That heatsink looks to be about 30 degrees per watt, so it can dissipate one watt for 30 degrees temperature rise, or two watts for 60 degrees temperature rise above ambient. So at two watts, on a hot day, the chip will be 90 degrees. You wouldn't want to run it hotter than that.

      So if you run it at two watts dissipation, and guesstimating 90% efficiency for a class-D (or similar) amplifier, gives 20W maximum power input with 18W maximum output (=2x9W rms output).

      20W from a 12V supply is 1.67 Amps.

      • That's fairly accurate but isn't the board output can handle a total of "100w"? Or is it actually limited to the ic's Max temp?

        • Because of the belief that "bigger is better", non-professional amplifiers have for many years used bogus figures for output power measurements. Most use a figure called "Watts PMPO", where PMPO stands for "Peak Maximum Power Output". It's a rubbish measurement, it's how much power the unit can put out for a single millisecond without failing. It doesn't even concern itself with "niceties" such as not having distorted audio.

          If you want to compare amplifiers, the figure to use is Watts rms at a distortion level of 1% or less.

          The IC's temperature will be the limiting factor for this amplifier.

        • @Russ:Thanks Russ for the detailed explanation :)

        • I purchased a TDA7498 amp from eBay and a power brick that's 24v 5A and it makes some great sound for the price. At a guess, I'd say this is a TDA7492 or a TPA3116. Should still be pretty good for the money.

        • but isn't the board output can handle a total of "100w"

          That would be short-term RMS output under certain conditions.
          Russ is talking about sustained average power limit.

          guessing the chip is a TDA7492:

          The TDA7492 is a dual BTL class-D audio amplifier with single power supply designed for LCD TVs and monitors

          50 W + 50 W continuous output power at
          THD = 10% with RL = 6 ohm and VCC = 25 V

          Suppose you really tried to sustain >50W continuous - e.g. a big air-raid siren, it would hit thermal limits.

        • @manic:

          I think you're being a bit too generous in your comment.

          THD = 10% with RL = 6 ohm and VCC = 25 V

          THD=10% means you're into "really noticeable distortion".
          http://www.avsforum.com/forum/90-receivers-amps-processors/9…

          RL=6 ohm was cherry-picked by the manufacturer to make the figures look better. Most home speakers are 8-ohm, most car speakers are 4-ohm. In defense of the manufacturer, this sort of chip is intended to be designed into TVs and similar devices, so the TV manufacturer will be able to source 6-ohm speakers.

          50W continuous - e.g. a big air-raid siren

          Logitech Z623 is 200W RMS, most home stereos are in the 10W-450W range
          https://www.logitech.com/en-au/product/speaker-system-z623
          10W stereo: http://www.lg.com/au/home-audio/lg-CM1560
          450W stereo: http://www.panasonic.com/au/consumer/home-entertainment/hi-f…

          As I mentioned above, this particular circuit will be limited by heat. The TDA7492 does say 90% efficiency, so my calculations still stand. If it had a much, much larger heatsink, as large as the entire circuit board and with fins ~25mm tall, I'd believe it could do the 100W claimed.
          http://www.st.com/en/audio-ics/tda7492.html

          However I don't think the chip is a TDA7492, that chip requires a minimum of 8V and has undervoltage cutout at 7V. ICstation claim the board works down to 4.5V, so it can't be the TDA7492.
          http://www.st.com/en/audio-ics/tda7492.html

          9+9W RMS will nicely fill a room with sound, as long as you are still able to have conversations in the room and you're not playing "doof doof" music. However it won't be enough for a party.

        • @m13:

          I reckon you're correct, the specs are very similar to the TPA3116. But this board won't do 50+50W, the datasheet for the TPA3116 specifies a much larger heatsink for that power level.

        • @Russ:

          THD=10% means you're into "really noticeable distortion".

          That only applies to the volume peaks though. 10% THD for the cannon shots in 1812 overture is no problem :-)
          Or the explosion effects in movies.

          Note the "designed for LCD TVs and monitors" part. That should set realistic expectations. These are great for making portable li-ion battery-powered portable speakers.

  • Rep, do I have to have tracking no and insurance ? I can't seem to remove it.

  • Rep, I can't even pass through the details page, I've been updating 3 times already. The price is not inclusive of postage, is it?

  • I have something similar to the BT Amp. I literally grabbed an old set of shelf speakers and hot glued it to the back. Used an old power brick and now thats my BT sound system in the kitchen.

  • +1

    After adding shipping, cheaper on eBay here and here

    • Thank you. Glad that I didn't buy it from icstation. The rep is non responsive. So, they lose the sale.

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