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How can I identify re-used electronic components? I need help with a guitar amplifier circuit as well. Answered


I want to make an amplifier based on the schematic in this instructable https://www.instructables.com/id/Make-a-Sweet-Portable-Guitar-Amp/. I wanted to add a power input jack so I left a comment on the instructable and the 'ibler replied and told me how to do that.

Now I am considering more possibilities, firstly, could I incorporate an led tuner? If so would it be best to just take a tuner apart and use that, could it share the same battery and mono guitar input jack?

Recently I took apart a cd player and salvaged two nice speakers, but they don't say how many watts they are they just say "QS" then "8Ω" and "5V". I don't think they will be suitable for this project anyway because they are 5v and I'm sure this circuit requires lower output voltages than that but i just thought i'd check. A label on the cd player said the power consumption for the device was 15W, can you work out the power of one of the speakers from any of this? Bearing in mind there were two speakers in total.

Another question, if I want to reuse resistors I know how to figure out their resistance using the colour bands and a resistance calculator etc. But is there a way of identifying what is a 1/4 watt resistor and what is a 1/2 watt resistor.


I'll bet the 5V is really 5W. Guess at around 10W RMS sound output.

Power rating can be guessed at from the size, but only by comparison between known samples, cheap resistors are often lower ratings that more expensive ones.

yeah i googled the device name and model that i took apart and it said it"features: 2 X 2 watts RMS" so that's 2 W per speaker?

RMS is the most you can apply to the speaker, i think only for a short amount of time. Yours are probably .5 or 1W speakers, with the instructable you mentioned, its actually quite underpowered. you could buy a higher powered chip (see instructable for part #), and it would be louder, otherwise i think you are fine. For a 3mm resistor i think it would be >=1/16 W. Its probably an 1/8w or 1/4 watt.

ok so i'm still none the wiser really i can't be entirely sure.

If i bought a higher power output chip, would it be wired exactly the same as in the instructable, because i really need something to follow step by step.

Also bearring in mind i am tryin to make the amp as small as possible, would the chip increase the size of the circuit significantl?

oh yeah, i just realised why it has low output. You need a lowish output otherwise it'll be too loud to use with headphones as well as built in speaker

As for your resistors, i think the half watt is usually slightly larger, but depends on the manufacturer and quality, so dont exactly make it your decisions based only on that :)

based on the sizes sated in my reply above (to '7654321') what wattage resistor do you think i have.

The power rating of the speaker is a maximum (like steve said its probably actually a W), so it's ok if the output is smaller.
The power rating of the resistor can be crudely determined by applying high voltages and marking when it starts smoking/stops working and then comparing that size to others.

I can now clarify that I have a resistor with the value I am after (1kΩ) and it is 3mm long.

Now what i would consider the usual size for resistors is about 5mm.

can you hazard a guess as to whether the resistor i have is right, i need a 1/4 watt resistor.