5
kurtr
2y

[Question]
What type of amplifier circuit would I need to power a 60w 8ohm speaker or can you recommend any prebuilt amplifier boards ?

[TLDR;]
I spotted the below stuff while cleaning out my junk cupboard and thought it might be a fun side project to convert them into a portable bluetooth speaker since the earphones are shit anyway and I've always wanted to learn more about amplifiers.

The only question remaining is how to amplify the headphone output signal enough to power the speaker. I plan on either using cells from old laptop batteries or a motorbike battery as a power supply so input voltage would be roughly 10-12v.

The speaker is from a set I salvaged from an old 80's hifi and has excellent sound quality, would mounting the components inside it have a large negative effect on it's sound?

Also although I would prefer to make my own amplifier board as a learning experience the goal is to have a portable speaker with good sound quality... is this something I'm likely to get from my first attempt at an amplifier or should I rather get a ready made board?

Comments
  • 3
    Summoning @condor
  • 2
    If you asking about the type of amps. personally, depends on what quality of sound you want to get, while considering the power efficiency. i alway build Amp type A and AB for my amusement.

    Power the amps is not as easy as powering high power PC, the quality of power supply really affect the output quality, using low quality psu means more noise. in my experience, amps circuit, especially type A, and C, don't like switching power supply; so i use Huge Transformer rectified by Full-Bridge Mosfet Rectifier and Huge Capacitor.

    And the structural quality of the amps really affect the sound output. even if you use same construction with different wood.

    i might be wrong tho, i'm no professional.
  • 1
    I haven't built amplifiers myself yet (but maybe I should, to use my phone/tablet/PC headphone jack as a makeshift function generator.. Afrotechmods has a tutorial on class D amplifiers which are apparently good enough for anyone that isn't an audiophile. They're quite efficient too. Only if you're going for the best of the best in audio quality, I'd go for an AB amplifier.. especially at 60W because the BJT's that it uses aren't very efficient, while MOSFET's in class D amplifiers are.
  • 0
    @Condor the only difference between class A, AB, and D amps is the power consumption, btw
  • 0
    @j4cobgarby i.e. efficiency when coupled with a particular driver :P

    It's kinda like a light bulb I guess, where a 400 lumen incandescent bulb will take a whole lot of power (60 watts or so) whereas a 400 lumen LED bulb will take much less power (a couple of watts, say 3-5W).. both give the same amount of light, but the power consumption i.e. efficiency is different.

    Speaker drivers are just inductors really (a coil with a permanent magnet in it that moves to make sound) and their power consumption only changes as you increase the amplitude i.e. voltage. For any given amplitude, its power consumption should be constant (similar to the light output in lights).. the driver's efficiency is the only thing that's different. BJT's being less efficient than MOSFET's, they'll obviously take more power for the same amount of usable sound.
  • 0
    @j4cobgarby No, class D amplifiers have a completly different working principle.
  • 0
    @bootleg-dev yes, and that working principle means it's the most power efficient of the designs
    But to be fair, the sound quality is different too
  • 0
    @j4cobgarby That was not even my point, but you said that the *only* difference is the power consumption, which is definitely not the case.
  • 2
    You could also make separate amplifiers for each element. It would allow for more precise tuning of the crossover. And maybe try Class D for the woofer and AB for the midrange and the tweeter.
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