Transfer a cellphone speaker unit into a useful audio monitor and signal tracer
Transfer a cellphone speaker unit (say between 8 and 20 Euro’s or Dollars) into a usable audio monitor (20 Hz-18 KHz) and signal tracer that can be connected to (say) Hi Fi speakers boxes in a hobby shack. There will be a dramatic improvement in audio reproduction when the chip is OK and has good properties and is able to drive a Hi Fi box. Preconditions: A) the speaker unit must be made in a “classical” way, so (in general, to keep it simple) earth is minus is ground. B) the used audio Chip must have normal/good properties (good frequency response) in the audio range, say between 50 Hertz and 15000 Hertz (15 KHz). This can be checked at first sight by looking at the speakers that are used in the box. When they have an “extra big” magnet you can be (almost) sure that the chip is able to reproduce the lower part of the audio spectrum (100 Hertz-500 Hertz) in a good way. C) the wall transformer that often supplies the speaker unit must be freed completely of any hum (!!). When the cellphone speaker unit is supplied via the computer via the USB it will be difficult to use this drawing/circuit. Of course it is possible to use a 110V/230 V USB power supply (few Euro’s) and then connect it to the series regulator/hum suppressor, but it is not sure that this will work due to the specific electronic properties from directly supplied USB supplies. D) Hum suppression means that the wall transformer must be followed by a series regulator that suppresses the hum in an extreme way, always necessary for audio circuits. Link is : • the transistor series voltage regulator pr... And E) the external speakers must be connected via a power resistor from 3 Ohms to prevent a burn-out from these fragile audio chips when they are shortcut at their (loudspeaker) output(s). With the help of switches we can switch both internal spakers off so that the chip only supplies (via the 2 series resistors from 3 Ohm) the external (Hi Fi) Loudspeaker boxes, left and right channel. Also: a signal tracer, that can be used with a diode head to detect AM signals etc. All the videos hat I have published on You Tube can be found via my Channel Trailer: Link is • Radiofun232 on YouTube, find working & tes... In thematic order you can find these video’s under the “comments” section. My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there. Link is https://www.lulu.com/shop/search.ep?k... My books are also available via Barnes and Noble and via Amazon. Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics) and important adaptations to the circuits. Be aware of that, I saw on the internet many of my circuits reproduced in a poor or even not proper way. I can not help that, sorry. Upload 8 april 2018.
