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I sent something similar to a friend who gave me two audio amplifier boards:-
I've failed with the PAM8403 audio boards. Removing the 22nF capacitors seems to tie output to supply Voltage. This may be due my poor unsoldering or the 22nF capacitors having oscillator functionality in addition to blocking DC drift from audio input. It may be possible to connect the 22nF capacitors to ground (for the purpose of oscillation?) and connect signal behind the capacitors (for the purpose of permitting DC drift for motor control).
People at my makerspace are quite amused that a turtle or tank robot could be controlled with stereo audio output and an 80 cent audio amplifier. Four or more PAM8403 chips multiplexed with a 4052 chip or suchlike and controlled with two or more GPIO pins would be particularly cheap but effective.
After a technical argument at the makerspace about Lego motor specifications, it was determined that approximately all Lego motors (from 3V to 9V, excluding servo motors) may be compatible with a PAM8403. This applies much more generally - if a PAM8403 chip can be made to work with a DC offset.
Also, two of the amateur radio enthusiasts and electronics experts at the makerspace were particularly impressed by the size and cost of PAM8403 boards. However, they confirmed that D-Class amplifiers cannot be ganged.
If anyone can get this working then you'll be *very* popular.
(Score: 2, Interesting) by xyz on Tuesday July 04 2017, @12:54AM
3W RMS will get you around 1A and 3VRMS of course (given a 5V supply rail as is the case here).
Class D single ended is basically a totem pole (push / pull, half bridge) driving a ground referenced LC.
But for bridge tied load connections as the PAM8403 data sheet shows (speaker tied between Left_Out+, Left_Out-) that'd translate to a half bridge output on each of the two BTL output drive pins, so a full H bridge being driven in something which may be anti-phase or may be a bit more complicated than than.
The "more complicated" could be taken in the direction of something like a phase-shifted full bridge topology (used in DCDC power conversion) or some multi-phase power conversion topology.
Anyway I just happened to be reminded of the topological similarities of a class-D half-bridge output stage with a synchronous buck converter, which is also a push-pull half bridge output stage driving an inductive (actually LC filtered, just like a speaker) output when it comes right down to it (and with an analog input controlling the output by a control loop -- the feedback pin). And there are some $0.10 price class (albeit only in full reel volumes) synchronous buck converters that run off of 5V and which can produce say 2A at 0.6V...5V output ranges and which are capable of 100% duty cycles and run at ~1 MHz rates (though the control loop / soft start stuff probably limits it in TBD ways). Granted those seem to be the single vs. dual / quad channel ones, and they'd have either too few or too many (depending on your perspective) built in "op amps" / amplifier / PWM loops to work just like an analog in to PWM Class-D out converter though the basic error feedback amplifier / triangle wave PWM generator / ... internal loop as the datasheets will depict is analogous and interesting. You could probably abuse the "feedback pin" maybe with resistive negative feedback from the output mixed with an external analog input to servo the output or something...maybe.
Keep in mind that a voltage source needs an inductive or resistive impedance and can't be connected to another voltage source and so the "Class D" totem pole outputs derived from the PVDD/GND rail voltage sources can't mix directly because they're just switched voltage sources. But just like in a multi-phase buck converter you can parallel voltage sources through an L or R or such.
So between Class-D (E, F, ...) , sigma delta modulators (see below), single/multi-phase buck converters, hysteretic converters, and on into even more exotic things there's plenty of fun to be had at low cost using "switching techniques" and low cost drivers. Which is a pet-peeve of mine why more devkits like mid-range Arduinos or something don't have at least one or more H-bridges / op-amps / comparators / FET drivers or what not or at least PCB footprints for "add it yourself" ones. A banner feature of most MCUs are the ever popular PWM outputs but they make it all but impossible to use them for anything interesting (3W "audio", motor control, ...) external to the MCU without another $0.25 of discrete analog/power components.
https://en.wikipedia.org/wiki/Class-D_amplifier [wikipedia.org]
https://www.digikey.com/products/en/integrated-circuits-ics/pmic-voltage-regulators-dc-dc-switching-regulators/739?FV=1c0001%2C1c0011%2C1c00c5%2C1c0109%2C1c0003%2C1c0004%2C1c0006%2C1f140000%2Cffe002e3%2C1bcc0069%2C1bcc006c%2C1bcc006d%2C1bcc006e%2C1bcc006f%2C1bcc0070%2C1bcc0071%2C1bcc0073%2C1bcc0074%2C1bcc0075%2C1bcc0076%2C1bcc0077%2C1bcc0078%2C1bcc0079%2C1bcc007a%2C1bcc007b%2C1bcc007c%2C1bcc007d%2C1bcc007e%2C1bcc007f%2C1bcc0084%2C1bcc0085%2C1bcc0086%2C1bcc0087%2C1bcc0088%2C1bcc0089%2C1bcc00fc%2C1bcc0003%2C1bcc0004%2C1bcc01db%2C1bcc01dc%2C1bcc01dd%2C1bcc01e5%2C1bcc01e7%2C1bcc01e8%2C1bcc01e9%2C1bcc01ea%2C1bcc01eb%2C1bcc01f6%2C1bcc01fc%2C1bcc0202%2C1bcc020b%2C1bcc020f%2C1bcc0210%2C1bcc0006&mnonly=0&ColumnSort=1000011&page=1&stock=0&pbfree=0&rohs=0&cad=0&datasheet=0&nstock=0&photo=0&nonrohs=0&newproducts=0&quantity=&ptm=0&fid=0&pageSize=100 [digikey.com]
https://www.digikey.com/product-detail/en/diodes-incorporated/AP3429KTTR-G1/AP3429KTTR-G1DITR-ND/5359835 [digikey.com]
https://www.diodes.com/assets/Datasheets/AP3429.pdf [diodes.com]
Anyway some things may be of interest also depending on how much you want to go down the rabbit hole of analyzing / simulating / modeling / repurposing / designing such things:
http://personal.strath.ac.uk/barry.williams/book.htm [strath.ac.uk]
https://www.scilab.org/scilab/features/xcos [scilab.org]
http://www.cppsim.com/ [cppsim.com]
http://www.linear.com/solutions/ltspice [linear.com]
http://www.electronicdesign.com/analog/signal-processing-density-domain-part-i [electronicdesign.com]
http://www.electronicdesign.com/analog/signal-processing-density-domain-part-ii [electronicdesign.com]
http://www.electronicdesign.com/analog/signal-processing-density-domain-part-iii [electronicdesign.com]
http://www.electronicdesign.com/analog/signal-processing-density-domain-part-iv [electronicdesign.com]
http://www.electronicdesign.com/analog/signal-processing-density-domain-part-v [electronicdesign.com]
http://www.electronicdesign.com/analog/my-favorite-modulator-only-needs-leftover-components [electronicdesign.com]
http://www.electronicdesign.com/analog/integrate-your-signals-digitizing-them [electronicdesign.com]
http://www.ti.com/lit/sg/sluw001f/sluw001f.pdf [ti.com]
http://ww1.microchip.com/downloads/en/AppNotes/01114A.pdf [microchip.com]
https://www.onsemi.com/pub/Collateral/SMPSRM-D.PDF [onsemi.com]
http://www.linear.com/product/LTC3861 [linear.com]