Thanks! I just make vector drawings in Inkscape/Adobe Illustrator!
Absolutely - these guys bridge together nicely, although as you'd expect power requirements shoot up (4 times the power, potentially). And four times the heat! You could also consider using them in parallel if you were sure to be driving only 4 ohm speakers.
Thanks! Yeah, also important to keep that resistor capable of handling greater-than-average power. While it won't have to dissipate the full force of the current being sent to the speaker, it could face a couple of watts worth of power in a very high power system - 1W for smaller chip amps, but 5W for larger ones is common.
Hey hey :P
Great question! For volume you'd use a single gang (mono) or dual gang (stereo) potentiometer - a variable resistor. This is the classic volume knob, which you typically include just after the audio input (image attached). The more anti-clockwise you turn the potentiometer, the greater the resistance introduced to the incoming audio signal, and the less signal there is to amplify in the rest of the circuit - and thus less volume.
Tales From the Chip: LM1875...View Instructable »
No problem! The LM1875 Instructable is almost finished, will be up in a day or two.
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Exactly! A few high power 8Ω resistors - with a switch to connect them in parallel for 4Ω - are the perfect way to test the muscle of a speaker amplifier.
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Yeah, the obsession with wattage as it relates to volume is really bewildering, but you can understand why the marketing departments need to latch on to something somewhat relatable. I honestly don't know why anyone would need a 300W speaker in say, their living room.
Hey John!Thanks - you spotted a typo. Changed that cap to "electrolytic" :)To add to your comment, although we don't tend to think this way anymore 100uf is actually a heck of a lot of capacitance, and really at the upper limit of what ceramics can offer reliably (and cheaply).However, it is a little-known fact that higher value ceramics also degrade at higher voltages, with greater variance and unwanted microphonic effects that electrolytics largely avoid. And considering that many audio applications require higher voltages (a typical DIY speaker amplifier might need +-24V) these effects start becoming relevant.So your rule of thumb is spot on - once you start getting into micro-farad territory, electrolytics should generally be considered.
Cheers - no problem! I've got a bunch of classic audio and general-use chips I'd love to write about, as well as some details about audio electronics in general.
Oh cool, that piggybacking idea is awesome, will investigate!
Thanks for your feedback! Cheers :)
Ha ha, yeah - I built the circuit before drawing out the schematic, so had the benefit of neatening things up and simplifying the layout somewhat. The two are electrically identical, however. And as long as the 0.1uF cap is between the output path and ground, it should still work like a charm. Thanks for the comment!
Yeah, I've got a pile of these lying around :) That being said, "old" doesn't mean "useless", and there is certainly a lot to be learned about audio electronics by understanding some of its more basic components, particularly one like the LM386 which has a very low barrier to entry. A great place to start, with little upfront cost and few extra components required. From there you can of course graduate to your dual LM4780 monoblock beasts!
You're correct! A more accurate term in my context would have been "loudness" as well as sound-pressure level (dB-SPL). That being said, dB is useful when talking relative terms or comparing levels, which was my intention here. I'll attempt to clarify :)
Extremely versatile little guy. Thanks!
Thanks for reading it!
Great, thanks man!
Great tutorial - clear and comprehensive. Nicely done!
Ha ha, blowing stuff up and starting again is all part of the fun. Thanks for sharing your build - seriously cool stuff. Jumpers are also a good idea - probably a safer option than my DIP switches.
Beautiful, elegant solution!
Sure thing. SPDT/DPDT are a shorthand to describing both the number of terminals that a switch connects, as well as the number of connections those terminals can make. For instance, a simple ON / OFF rocker switch might be a SPST (single pole, single throw) switch. It would have one terminal connected to the circuit in the ON position, and no terminals connected to anything in the OFF position.A power switch that needs to connect or disconnect both the LIVE and NEUTRAL wires might be best suited as a DPST switch (double pole, single throw). In the ON position, both wires are each connected to the circuit, and in the OFF position both wires are connected to nothing.Finally, a switch that has to route two terminals to different parts of a circuit might be a DPDT switch. In the A position ...
Sure thing. SPDT/DPDT are a shorthand to describing both the number of terminals that a switch connects, as well as the number of connections those terminals can make. For instance, a simple ON / OFF rocker switch might be a SPST (single pole, single throw) switch. It would have one terminal connected to the circuit in the ON position, and no terminals connected to anything in the OFF position.A power switch that needs to connect or disconnect both the LIVE and NEUTRAL wires might be best suited as a DPST switch (double pole, single throw). In the ON position, both wires are each connected to the circuit, and in the OFF position both wires are connected to nothing.Finally, a switch that has to route two terminals to different parts of a circuit might be a DPDT switch. In the A position two terminals are connected to one part of the circuit, and in the B position the same two terminals connect to a different part of the circuit.Sparkfun has a good explanation here:https://learn.sparkfun.com/tutorials/switch-basics/poles-and-throws-open-and-closed
Spot on - you'd need to select the potentiometers quite carefully, but that would work no problem. As for a little on-board voltmeter you would almost certainly have a small forward voltage drop you'd have to work around, but of course with the potentiometers you can just dial it a little higher and maintain the output you need.
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Tales From the Chip: LM386 ...View Instructable »
Awesome! Looks great - love the inclusion of the battery.
Awesome, looks great!
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Cheers! Such a great little idea
Your design is lovely - simple, minimal, but striking. Looks like a genuine piece of high-end equipment. Well done!
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Dang, will keep that in mind ;) Thanks for the feedback!
Thanks very much!
Thanks so much for the kind words, and I'm glad it was useful to you. Good luck, looking forward to seeing your results ;)
Thank you very much!
Yeah, my board is certainly light on protection and safety features - noted! The LM317 has a max current output of 1.5A, even if fed with more current, otherwise flipping the passtrough switch and bypassing the IC will give you as much current as your power brick can provide.
Phwoooar, that is a seriously cool design - love the plug-n-play idea there. Such great work!
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