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2.1 "Smart-amp" with DSP

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  • 2.1 "Smart-amp" with DSP

    This is a fun project for a desktop computer sound system. It uses a 2-input, 6-output DSP board for active crossovers, EQ, BSC, and bass enhancement. It's stereo analog input with stereo 3-way output, but I'll be using it as an active 2.1 system, with woofer and tweeter channels for left and right small speakers on the desktop and a sub box with dual subs under the desk.

    All of the DSP functions are controlled from a cell phone using a Bluetooth link. I've got a new version of the cell phone app written with Android Studio, and it isn't complete, but it is moving along. The old app written with MIT App Inventor still works, though.

    Click image for larger version

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    The DSP board is on the left, with a Bluetooth board plugged in. There is also a socket for using a WiFi board for control instead of the Bluetooth.

    The back of the amp is simple enough: two 4-pole Speakon connectors for left and right woofer/tweeters, and another Speakon connector for the two sub drivers.

    Click image for larger version

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    The chassis is from a prototype Virtue Audio Sensation amp--it's a nice chassis that I couldn't bear to toss. I didn't take a picture of the top, but it is a nice veneer-covered MDF cover that won't block the Bluetooth signal. But since the box is "sealed, I needed to use heat pipes to draw the heat from the amp heatsinks. The heat pipes do a good job of sinking the heat to the back and side panels..

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    The three main components are all items that I wish PE would stock. First, the power supply is a Meanwell UHP-200, which is much smaller than the "standard" Meanwell 24V 200W supplies. The small form factor of this series is much better suited to making compact power amps, and it would be nice to have them available at PE. Second, the 6-channel amp is one of those $25 "5.1" amps that are advertised as 4x50W + 2*100W. PE sells the Sure 6-channel amp with the TDA7492 chips, but these amp boards are smaller and use the TPA3118 chips with good quality film caps in the output filters. It would be nice to see this product along with the Sure board available at PE. And third, that DSP board with cell phone control is pretty cool and would make a nice product. I need to talk with PE about this...

    Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

  • #2
    Wow Neil - this looks amazing!
    Where can you pick up the Meanwell supplies? (edit: easily found at Mouser or Digikey) Is the 6 channel Sure board at PE ok in your opinion?

    Thanks and again, really excellent project!

    Comment


    • #3
      PE stocks Meanwell PSUs, but not those.
      Wolf
      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
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      • #4
        Thanks.

        The 6 channel Sure board is well built, with a sturdy heatsink and a thicker board and better mechanical parts than the $25 eBay amp. But it uses ceramic capacitors in the output filter, which turned me off. Trevor Marshall took measurements of a Sure TDA7498 amp before and after replacing the ceramic caps with stacked polys, and the difference was an order of magnitude in measured distortion. I don't know how audible the difference is, but just knowing that the measured performance was so much better with the poly caps prompted me to replace them. That added a lot of time and some cost to the board. Also, the best way to take advantage of that nicer heatsink is to remove the fan and mount the amp upside-down with standoffs that allowed thermal contact of the heatsink with the chassis. But in order to do that, you need to unsolder all of the speaker connectors from the top of the board and solder them to the bottom of the board--otherwise, you can't get to the screws. That's what I did for the plate amp version of this amp project (see pic below).

        The eBay amp is cheaply made, but it uses poly caps in the output filter, so it has that advantage. Also, it uses the TPA3118 chips, which some people prefer, although for me that is not a big decision-driver. But the price difference is important--even at twice the price it would be a "good deal" for a 6-channel power amp. If PE could sell a version with a heatsink that could easily be bolted to a chassis, it would be even better!


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        Last edited by neildavis; 12-04-2018, 08:22 AM.
        Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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        • #5
          That's an awesome project Neil. It looks so neat too... not like my usual birds nest of jumbled lines. Forget about pushing DIY boundries, that's advanced for retail I think.
          are the copper tubes filled with anything to help transfer heat? I haven't seen that done before, that's a cool trick.
          TomZ
          Last edited by tomzarbo; 12-04-2018, 01:20 PM.
          Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
          *Part 2 *Gluing multiple curved laminations of HDF

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          • #6
            Thanks.

            The heat pipes are available at Digikey or Mouser. They come straight and sealed, filled with distilled water to transfer heat via vaporization. You have to buy the right length and bend them yourself.

            The challenge is bending them without kinking, which I failed at for the one on the right. HomeDepot/Lowes sell tubing benders for about $14 that work fine for the round heat pipes, but don't work well for the flat ones. You can mix some 5-minute epoxy with thermal compound (the white stuff available for CPU heatsinks) to make your own thermal epoxy. The thermal epoxy can be used to "attach" the heat pipes, and it fills the gaps for better heat transfer.
            Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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            • #7
              Awesome.
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              • #8
                We need more of this!! From soundbars to boomboxes, this is the future PE. Problem is, outside of the amps, what is available for DSP and Bluetooth/Source is too often flawed as we saw with the Sure DSP and that BT/radio for $15 which has too much noise (relegated my bedroom radio to the garage because of this). Would be nice to see PE develop a modular ecosystem, where you have Source in one unit, DSP in another, and amps in another, and you can just plug and play according to your power needs.
                ~Brandon 8O
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                • #9
                  Originally posted by neildavis View Post
                  Second, the 6-channel amp is one of those $25 "5.1" amps that are advertised as 4x50W + 2*100W. PE sells the Sure 6-channel amp with the TDA7492 chips, but these amp boards are smaller and use the TPA3118 chips with good quality film caps in the output filters.
                  Great project! Given the description about, I'm having trouble sourcing the amp you specify. Could you be a little more specific? thanks

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                  • #10
                    never mind, tried another direction and found it.

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                    • #11
                      Neil, you always come up with interesting projects! Nice job on this one.
                      Charlie's Audio Pages: http://audio.claub.net

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                      • #12
                        Originally posted by charlielaub View Post
                        Neil, you always come up with interesting projects! Nice job on this one.
                        Hey Charlie, how ya doing these days? Thank you for hosting all those wonderful DIY get togethers.

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