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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ICStation, China

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  pyramid on 13/10/2017 - 16:40

  Store name in title pls.

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  rtk74 on 13/10/2017 - 17:50

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

  • 

    bargaino on 13/10/2017 - 18:20

    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?

    • 

      rtk74 on 13/10/2017 - 18:24

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

  • 

    Russ on 13/10/2017 - 20:19

    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.

    • 

      rtk74 on 13/10/2017 - 21:06

      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?

      • 

        Russ on 13/10/2017 - 21:16

        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.

      • 

        rtk74 on 13/10/2017 - 21:32

        @Russ:Thanks Russ for the detailed explanation :)

      • 

        m13 on 13/10/2017 - 21:44

        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.

      • 

        bargaino on 14/10/2017 - 10:28

        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.

      • 

        Russ on 14/10/2017 - 13:46

        @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.

      • 

        Russ on 14/10/2017 - 14:13

        @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.

      • 

        bargaino on 14/10/2017 - 15:04

        @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.

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  apprentice on 14/10/2017 - 00:04

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

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  rtk74 on 14/10/2017 - 00:51

  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?

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  Troposa on 14/10/2017 - 09:17

  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.

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  bamzero on 14/10/2017 - 17:48

  +1

  After adding shipping, cheaper on eBay here and here

  • 

    apprentice on 14/10/2017 - 19:19

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