Thanks! I just make vector drawings in Inkscape/Adobe Illustrator!
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.
Hey hey :P
No worries, thanks for reading!
Awesome! For integrating into smaller form factors, I'd seriously consider Class D amplifiers over Class A/B. Far more efficiency means less heat (and less heatsinking), lower voltages for equivalent volumes and (often) fewer components needed. However, the best Class D chips are typically SMD/SMT devices, which can be trouble if you're used to through-hole components. Try the TPA3125 from TI to see what can be done! (http://www.ti.com/lit/ds/symlink/tpa3125d2.pdf)
Tales From the Chip: LM1875 Audio AmplifierView Instructable »
No problem! The LM1875 Instructable is almost finished, will be up in a day or two.
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Thanks for the feedback! I deliberately use both terms in the article. I use "resistance" to refer to the resistors themselves and considerations around which ones to use (for the sake of avoiding confusion), but as "impedance" with regards to how an amplifier or source "sees" the load in an AC circuit, which is actually the more correct usage. Check this out for clarity!http://www.electronics-tutorials.ws/resistor/res_8.html
Thanks! Yeah, I've become an instrumentation nerd recently - they seriously help speed up prototyping. Cheers!
Headphone Dummy LoadView Instructable »
DIY External Volume ControlView Instructable »
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!
Extremely versatile little guy. Thanks!
Great, thanks man!
Thanks for reading it!
Great tutorial - clear and comprehensive. Nicely done!
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.
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!
Thanks for the feedback - yeah, no doubt jumpers are the safer option. I like to live dangerously, apparently! Fortunately I haven't had a DIP switch accident yet ;)
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Tales From the Chip: LM386 Audio AmplifierView 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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Thanks @itzzzmee! My variable power supply needs are a little different - I work a lot with DIY audio projects, where a higher powered amplifier can often require around ~36V, if not higher. So my DIY variable supply will need to be pretty beefy. When I get around to making that, I'll stick it on Instructables too. Thanks for the comments!
Awesome, thanks very much! Hope you get around to making one (or something like it) soon!
Oh wow, this is awesome! Thanks for crunching the numbers - this is by far preferable. Well done, thanks for sharing!
Thanks very much!
Great suggestion. I recently had the (adventure?) of wiring up a 3 position, 4 pole rotary switch for an amplifier, and I must admit things got a bit hairy, so perhaps the DIP switch was my attempt to keep it simpler in construction!
Amen brother! You beat me to it - I'm busy working on a little chop-shop step-down converter using salvaged parts. Will put up a walkthrough when I'm done!
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