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  • Make Your First Serious Amplifier

    It's possible. Consider starting with a bare circuit board from ebay, or a kit, or even a completed board. Bare PCBs are dirt cheap, and will make for a much neater build.

    Not impossible, but it's unlikely to be cost-effective compared with buying an amp (new or used). The LM3886 can be paralleled to increase the current (and handle lower impedance loads), and then bridged to double the voltage swing (and roughly quadruple the power).

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  • If the gear doesn't have a set screw, you could drill and tap it. Or, maybe drill a hole through the gear and the shaft and lock them together with a split pin.

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  • 4x4 mini-truck or body-on-frame SUV? Look for one with a rusted-out body but decent chassis and running gear, and hopefully some aftermarket upgrades.

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  • I'd make a rough cut around the drum with a sabre saw, then fit a piece of plywood (or mdf or particle board) in the end (somehow), then position my router to trim the rough edge flat (space the router (which has an extended base) off the plywood with a scrap of mdf).

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  • Pretty much every "high power" head unit is only doing about 10 to 15 watts RMS per channel. Read the fine print in the specs. So, you can pretty much ignore the "watts" in the ads. As for speakers, power ratings are even less well defined. You can get a hint of the real power handling ability by looking at voice coil diameter; bigger voice coils can handle more heat. And require bigger and more expensive magnet structures. The only way that speakers influence power amplifier clipping is by their efficiency (or sensitivity); a less efficient speaker will need more power to play as loudly as an efficient speaker.I'd avoid the sort of brands sold at big box stores (like Dual) and go with stuff that car audio specialists are willing to sell (they sometimes have barg…

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    Pretty much every "high power" head unit is only doing about 10 to 15 watts RMS per channel. Read the fine print in the specs. So, you can pretty much ignore the "watts" in the ads. As for speakers, power ratings are even less well defined. You can get a hint of the real power handling ability by looking at voice coil diameter; bigger voice coils can handle more heat. And require bigger and more expensive magnet structures. The only way that speakers influence power amplifier clipping is by their efficiency (or sensitivity); a less efficient speaker will need more power to play as loudly as an efficient speaker.I'd avoid the sort of brands sold at big box stores (like Dual) and go with stuff that car audio specialists are willing to sell (they sometimes have bargain tables). Or with used name-brand stuff from thrift stores, pawn shops, auto wreckers, swap meets.

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  • Another option is, get a PCI serial card from a computer recycler, or buy a new PCIe card (if no PCI slot). Or, chances are that any software that needs a serial (or parallel) port will run fine on an ancient computer and maybe not at all on Windows 10, so keep a small desktop, embedded or POS (point of sale, not the other p.o.s.), or laptop computer around with Windows XP to run that stuff.

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  • This could be a job for the MQTT protocol, where sensor clients (like ESP-8266) talk to a central hub or server (Raspberry Pi). WiFi on the ESP-8266 may be too power-hungry, but it's a start: you can buy Sonoff modules off-the-shelf with temp and humidity sensors. Bluetooth Low Energy would presumably use much less power, but I know too little about BLE to suggest what to use.https://iot.stackexchange.com/questions/1825/is-mqtt-protocol-appropriate-for-transmitting-sensor-readings-over-ble/1827

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  • I'm pretty sure most of the Hauppauge WinTV PCI TV tuner and capture cards ignore the Macrovision protection. (They also handle both NTSC and PAL video formats, if you have a foreign camcorder and tapes.) PCI capture cards could be found at computer recyclers like Freegeek.

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  • Weight? That would just require putting a little platform or maybe a smaller tube within the tunnel with a load cell underneath. A quick search on ebay finds HX711 load cell interface boards and 10 kg load cells for under $5 total.I don't think visual (or ultrasound) measurements would be as useful, since rats are very flexible and stretchy.

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  • Also, signal to noise measurements, and frequency response. RMAA could do that using a computer sound card, except there is the problem of the bridged output. I'd try a sound card with optical input and a battery-powered ADC with optical output (eBay, analog digital audio converter).I suspect performance will be unimpressive, since there's no feedback. Suitable for a vehicle PA horn or siren, the kinds of music production applications where distortion is a good thing, or a science fair project. If you actually want to listen to music, there are awesome little class-D amp boards from China for the price of a burger combo.

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  • In my experience, solder gives way or flows under pressure so that screw or clamp terminals don't stay tight. It's better to put a ring or fork or ferrule terminal on the wire, as appropriate. If that's not practical, then just solder the very tip of the wire to prevent fraying.

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  • there's a bunch of potential reasons for linking the radio into the vehicle bus. discouraging aftermarket stereos, theft protection, knowing when the headlights are on, different eq profiles for different models or perhaps according to speed or window or convertible top position. I'd guess this stuff started happening in the mid-'90s. radios from the '80s would be safe bets, and not so old that wrecking yards would call them collectible.

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  • Some late model car radios aren't usable unless they're connected to the car's computer bus. I don't know when that became a thing. They do it because it simplifies connections to steering wheel controls, and because a radio can automatically use different EQ curves for different vehicle models, and stuff.

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