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TPA3116 2.1 Amp - Step by Step Modifications

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  • tomzarbo
    replied
    Mike, thanks for spending the time to do this. The ratio of "2" to ".1" wattage figures are right on and the adjustability of xover points makes this a pretty nice setup.
    Why, oh why don't they set these up this way from the start?

    TomZ

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  • DanP
    replied
    Nice job Mike. Looks like the perfect 2.1 amp after your mods.

    Dan

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  • Millstonemike
    started a topic TPA3116 2.1 Amp - Step by Step Modifications

    TPA3116 2.1 Amp - Step by Step Modifications

    I've discussed this amp before in posts but here is it is all in one place.

    I used this dual chip, 2x50w & 1x100W amp in a 2.1 boombox build. I feed it with 26v or 25v (SLA-AGMS versus LiPos) and run it hard on the beach. One full season without any issues running 2x35W and 70w (140w total).

    The amp uses one chip for the ".1" sub channel and has a fixed, sallen-key topology 2nd order LP filter with Butterworth damping. On my board, the LP F3 was 107hz. I've successfully modified that filter by replacing 2 box poly caps. In the schematic, you can see a table of possible F3s given standard value capacitors. I added a legend to the amp's picture to cross refrence with the schematic.

    The amp has an audio frequency bandpass filter, strangely, only on the sub channel. Unfortunately, the F3 of the 1st order HP section is set at ~34Hz limiting low frequency. This is easily solved by replacing two 1uf electrolytic caps with a 4.7uf ones - same physical can size. That lowers the HP F3 to ~ 7hz.

    There are two 1uf signal coupling caps between the L-R input volume pot and the chip's input. With the chips impedance impedance (30K w/gain set at 26dB), these caps form a 1st order HP, F3 = 5hz. The schematic has a table with cap values for increasing that F3 relieving the L-R speakers from some bass duty.

    The chip's gain is set 26dB. My PC output drove to full volume as would most line outs. But my my phone's headphone out was weaker and I needed to front end it with a Sure headphone amp for additional gain. Easy enough to front end that with a Sure BT module if you care (though that requires 12v power, a issue to resolve).

    The front panel switch is Standby - On (not off on). Using this switch, there isn't a turn on/off thump. Leaving this switch in the on position and switching power will cause a thump.

    Lastly, there are similar boards based on the same core design. Most notably the version with 3 PS bypass caps instead of one. Coming from different manufacturers, the triple cap board has exhibited problems with component population causing several problems (chips not in sync mode, sub LP filter at 1Khz, etc.) And, apparently on fleabay: "what you see is what you get - NOT." One guy received a different amp than pictured. So, YMMV.

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