LM 386 as audio amp. 0,5 Watt, connected to the headphone out, more considerations (SW listening)

Please read the description first. Again about that LM 386 Chip, gives out max. 0.5 Watt audio.
More info in the final text of this description about my experiments to make a simple and good quality audio filter with a 1 or 1.5 Watt audio end amplifier, that can be connected to the headphone out of a computer, when it receives SW signals, via SDR (Software Defined Radio). 3 okt 2024.

More info there, in that first vid. Also in the links in the descriptions there.

In reality, undistorted audio is say 300 mW out.

Correction: I tell in this video now (30 sep 2024) that the "adaption potmeter/trimmer" to the input of the LM 386 Chip was 47 K but it was 25 K. I think it will not differ much, in practice.

I show here a second experiment with that LM 386 Chip. That chip + its datasheet can be found everywhere on the www/internet. The “problem” with this chip is that its audio output to a loudspeaker with an impedance in the order of 4-16 Ohms (DC, nominal), in fact, is somewhat (too) small.

With loudspeakers that have a good amount of energy-out when driven by a small voltage (say their efficience/rendement) it can work OK. But with low-efficient loudspeakers it could be a problem to hear the nuances in the audio or music, via that 300 mW (normal) or (max. 500 mW) LM 386 Audio Chip.

For a Shortwave Radio inteligibility is key. It means: properly (fierce) reproducing in the range between (say) 800 Hertz and (say) 4 KC (KHz), that is the typical “audio range”. All other frequencies in that audio band (that goes, completely, in theory, between 20 Hertz-20 KC) must be pressed down to a not-relevant level.

Thus, in terms of audio “hearing”, that makes voices (and music with a limited audio range) good intelligible. And: that audio amp that does that job must have a low noise level. Though the properties of the human ear (able to filter that noise out naturally, scientific proven) play a big role here.

It means, in practice, that you need an audio ”bandfilter”. That is not showed here & now, but it can be made with Opamps or a few transistors.

Many circuits of such audio bandfilters with a peak between 800 Hertz and 4000 Hertz are on the www. Perhaps that will be my second project, though there are many audio bandfilters (with their bandwidth calculations) published on the www.

They realize, when listening, in this audio “range” the typical (old school, by the way) “telephone” sound, made (via audio filtering) the human speech (man/women, studied via their different audio profiles when talking) good intelligible.

It all has and had (in the past & now) much to do with the bandwidth that is/was possible/usable via speech communication via satellite, glass fiber, or copper lines (coax and so) to where we live. Thus receiving telephone calls & making the www. working all over our earth, so that we can talk via our (smart) phones. And do much more: direct TV communication with sound etc.

Bandwidth is here and now “key” and a higher bandwidth comes with a price, you pay for that via your abonnement/subscription via a certain provider of your smartphone.

Anyway: these “wires” and the non-wired transmission of signals (HF, VHF,UHF) all have specific properties, based on physics.

Type there the keywords that you like (e.g. radio/audio/amplifiers/test/filter/) in the “looking glass” = search function” and give “enter”. Via that you can find specific video’s (under the say 1500 published).

When you search, search always “NEWEST FIRST” to get the right overview.
You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.

I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims. Upload 30 September 2024.

NB (update) I developed a much better circuit during the past days, working with a 1 Watt audio output and a sound (noise reduction) filter, going from the headphone output of the computer to that 1 Watt audio Amp. I will publish that ASAP (now 3 okt 2024).

[radiofun]

Completely transparent (for audio frequencies) loudspeaker cloth is mosquito netting/nylon mesh. That is what I have used here/now in the final circuit. It works OK. Use the type of maze-width of (say) 1 mm or so. I used the type of mesh where the wires are "welded". It makes it easy to use. 1 Oct 2024.

[commandoPR]

I have built a guitar amp using LM386, two of them, in a bridged configuration. Super easy IC to work with!

[td]

As a coincidence, I am working on this exact same project and application. I stream movies, over the web. The audio of older movies' was not designed with digital electronics in mind and their sound can be too low for my old ears. I am using my DIY LM386 amp - It is open source from YTer John Audio Tech. And very similar 3" speakers. I am putting those into their own boxes. The PCBs are being manufactured, as we speak. Thank you for sharing.

[acestudioscouk-Ace-GACE]

Interesting project and results. Thanks for the notes too and I look forward to your next update.

[td]

Tip = The computer audio output is stereo. If you only have one of your amp and speaker arrangements, you need to remember to set the computer output to monaural, or set the speaker pan function completely over to the output channel that you are using, or, better yet, build a second amp and speaker arrangement, to be able to listen in stereo. I like the last, best = grin. HTH.